About the Fish Study

By Chuck Yonker




Picture 1. Ryerson Lake,  July 2014

 Study performed: 24-25 July 2014

Final report submitted: 15 January 2015

Prepared by: David J. Jude, Ph.D.,

Limnologist, Fishery Biologist



5293 DANIEL, BRIGHTON  MI  48114 P:810-227-6623

Table of Contents











Depth. 6

Acreage. 6

Hydrographic Map. 6

Sediments. 7

Light Penetration. 7

Temperature. 7

Stream Flows from Inlets and Outlets. 7


Temperature Stratification. 8

Dissolved Oxygen. 9

pH.. 11

Alkalinity. 11

Hardness. 12

Chlorides. 12

Phosphorus. 12

Nitrogen. 13


Algae. 13

Macrophytes. 14

Zooplankton. 14

Benthos. 15

Fish. 15





Depth. 21

Acreage. 21

Light Penetration. 21

Temperature/Dissolved Oxygen. 21


pH.. 24

Chlorides. 24

Phosphorus. 24

Nitrates. 25

Ammonia. 25

Hydrogen Sulfide. 25

Conductivity. 2626


Algae. 26

Aquatic Macrophytes. 27

Zooplankton. 27

Fish. 30



  1. Nutrient inputs. 54
  2. Northern Pike. 54
  3. Largemouth Bass. 54
  4. Yellow perch. 55
  5. Walleye. 55
  6. Prevent Exotic Species from Entering Ryerson Lake. 55




Appendix 1.  Guidelines for Lake Dwellers; some may not apply. 56












PICTURE 1.   Ryerson Lake

PICTURE 2.   Starry stonewort

PICTURE 3.   Zooplankter, copepod

PICTURE 4.  Zooplankter, Daphnia

PICTURE 5.  Trap net

PICTURE 6.   Some fish caught in Ryerson Lake

PICTURE 7.   50-ft seine

PICTURE 8.   Gill net




Table 1.  Listing of times various nets were set in Ryerson Lake

Table 2.  Listing of station descriptions for Ryerson Lake

Table 3.   Dissolved oxygen/temperature profile, summer

Table 4.  Conductivity, pH, chloride, and nutrient data, 24 July 2014

Table 5.  Zooplankton data, station A

Table 6.  List of fishes caught

Table 7.  Diets of fish examined

Table 8.   Raw fish age data

Table 9.  Summary table






FIGURE 1.  Temperature relationships over time

FIGURE 2.  Dissolved oxygen relationships over time

FIGURE 3.  Google map of Ryerson Lake

FIGURE 4.  Hydrographic map of Ryerson Lake

FIGURE 5.  Map showing location of sampling stations

FIGURE 6.  Dissolved oxygen/temperature profile for Ryerson Lake

FIGURE 7.  The high temperature/low dissolved oxygen squeeze put on fishes

FIGURE 8.  Bluegill age data: Ryerson vs. MDNR

FIGURE 9.  Largemouth bass age comparison: Ryerson vs. MDNR

FIGURE 10. Yellow perch age comparison: Ryerson vs. MDNR

FIGURE 11. Green sunfish age comparison: Ryerson vs. MDNR

FIGURE 12. Pumpkinseed age comparison: Ryerson vs. MDNR

FIGURE 13.  Walleye age comparison: Ryerson vs. MDNR

FIGURE 14. Northern pike age comparison: Ryerson vs. MDNR





Appendix 1: Guidelines for lake dwellers











We were asked to perform a fishery investigation of Ryerson Lake located near Fremont, MI in Newaygo County, and to develop short-term and long-term management plans for the lake. Ryerson Lake is a eutrophic lake with mostly shallow littoral zone with an 80 - ft deep hole in the middle of the lake.  The lake is ringed with many houses located around the lake, but there is a large area owned by YMCA that is relatively undeveloped on the east side of the lake.  There is a considerable amount of sand and gravel in and along the shores along with extensive beds of aquatic plants, which can act as good habitat for insect prey and good spawning sites for sunfishes.  There are four inlets and one outlet which can act as good spawning sites for spawning, migrating species, such as white suckers and northern pike.

The lake is a 292-acre lake according to MDNR.  The dissolved oxygen measurements we took showed that at the deep spot, there was a thermocline between 9.8 ft (3 m) and 13.1 ft (4 m) and there was little or no dissolved oxygen at 16 ft (5 m) and below.  Hence there would be no fish below 16 ft in this area.  Zooplankton results are not available yet.





The lake has been monitored by Progressive Engineering and the aquatic plants managed as well.  Their data and ours show the lake has a considerable buildup of phosphorus and nitrogen in bottom waters during summer and probably winter stratification periods.  Those nutrients are then re-distributed throughout the lake during spring and fall overturn promoting plant algae growth.




Our study involves physical, chemical, and biological measurements and observations by professional aquatic biologists who have conducted lake management studies since 1972; we incorporated in 1974.  We use specialized samplers and equipment designed to thoroughly examine all components of an aquatic ecosystem.  Shallow water, deep water, sediments, animal and plant life as well as inlet and outlet streams are intensively sampled and analyzed at several key stations (sites on the lake).  Some samples are analyzed in the field, while the balance is transported to our laboratory for measurements and/or identification of organisms found in samples.

After the field study, we compile, analyze, summarize, and interpret data.  We utilize a comprehensive library of limnological studies, and review all the latest management practices in constructing a management plan.  All methods used are standard limnological procedures, and most chemical analyses are according to Standard Methods for the Examination of Water and Wastewater.  Water analyses were performed by Grand Valley State University.



During any study we choose a number of places (stations) where we do our sampling for each of the desired parameters.  We strive to have a station in any unusual or important place, such as inlet and outlet streams, as well as in representative areas in the lake proper.  One of these areas is always the deepest part of the lake.  Here we check on the degree of thermal and chemical stratification, which is extremely important in characterizing the stage of eutrophication (nutrient enrichment), invertebrates present, and possible threats to fish due to production of toxic substances due to decomposition of bottom sediments.  The number and location of these stations for this study are noted in that section.







Depth is measured in several areas with a sonic depth finder or a marked sounding line.  We sometimes run transects across a lake and record the depths if there are no data about the depths of the lakes as we did in this study.  These soundings were then superimposed on a map of the lake and a contour map constructed to provide some information on the current depths of the lake.




Acreage figures, when desired, are derived from maps, by triangulation, and/or estimation.  The percentage of lake surface area in shallow water (less than 10 feet) is an important factor.  This zone (known as the littoral zone) is where light can penetrate with enough intensity to support rooted aquatic plants.  Natural lakes usually have littoral zones around their perimeters.  Man-made lakes and some reservoirs often have extensive areas of littoral zone.


Hydrographic Map


A map of the depth contours of the lake was prepared for Ryerson Lake, since there was no prior one and because the depths changed due to dredging.  We secured starting and ending GPS values for transects across the lake and then ran the pontoon boat at a consistent speed and measured the depth every 5 sec until the opposite shore was reached.  These depth data were recorded and later entered on each of the transect lines drawn across a copy of the lake map showing the lake shoreline outline.  The distance of the transect line (in mm) was divided by the number of observations for each transect so that the depths could be assigned accurately to the line at equal intervals.  Next we interpolated contour lines based on the depth contour of interest, including lines for 5, 10, 15, 20, and 30 ft.  This map will assist us in making assessments of the lake and hopefully fishers who want to fish in specific depths on the lake.




Bottom accumulations give good histories of the lake.  The depth, degree of compaction, and actual makeup of the sediments reveal much about the past.  An Ekman grab or dredge sampler is used to sample bottom sediments for examination.  It is lowered to the bottom, tripped with a weight, and it "grabs" a 1 square foot sample of the bottom.  Artificial lakes often fill in more rapidly than natural lakes because disruption of natural drainage systems occurs when these lakes are built.  Sediments are either organic (remains of plants and animals produced in the lake or washed in) or inorganic (non-living materials from wave erosion or erosion and run-off from the watershed).


Light Penetration


The clarity of the water in a lake determines how far sunlight can penetrate.  This in turn has a basic relationship to the production of living phytoplankton (minute plants called algae), which are basic producers in the lake, and the foundation of the food chain.  We measure light penetration with a small circular black and white Secchi disc attached to a calibrated line.  The depth at which this disc just disappears (amount of water transparency) will vary between lakes and in the same lake during different seasons, depending on degree of water clarity.  This reference depth can be checked periodically and can reflect the presence of plankton blooms and turbidity caused by urban run-off, etc. A regular monitoring program can provide an annual documentation of water clarity changes and also a historical record of changes in the algal productivity in the lake that may be related to development, nutrient inputs, or other insults to the lake.




This is a physical parameter but will be discussed in the chemistry section with dissolved oxygen. Thermal stratification is a critical process in lakes which helps control the production of algae, generation of various substances from the bottom, and dissolved oxygen depletion rates.


Stream Flows from Inlets and Outlets


Estimation of flows in and out of a lake gives us information about ground water inputs, inputs of nutrients and toxic substances, and amount of water moving through the ecosystem.  When tied to the chemical analyses described earlier, nutrient inputs and outputs can be calculated and amount of impact of these inputs evaluated.





Water chemistry parameters are extremely useful measurements and can reveal considerable information about the type of lake and how nutrients are fluxing through the system.  They are important in classifying lakes and can give valuable information about the kind of organisms that can be expected to exist under a certain chemical regime.  All chemical parameters are a measure of a certain ion or ion complex in water.  The most important elements--carbon (C), hydrogen (H), and oxygen (O) are the basic units that comprise all life, so their importance is readily obvious.  Other elements like phosphorus (P) and nitrogen (N) are extremely important because they are significant links in proteins and RNA/DNA chains.  Since the latter two (P and N) are very important plant nutrients, and since phosphorus has been shown to be critical and often times a limiting nutrient in some systems, great attention is given to these two variables.  Other micronutrients such as boron, silicon, sulfur, and vitamins can also be limiting under special circumstances.  However, in most cases, phosphorus turns out to be the most important nutrient.


Temperature Stratification


Temperature governs the rate of biological processes.  A series of temperature measurements from the surface to the bottom in a lake (temperature profile) is very useful in detecting stratification patterns.  Stratification in early summer develops because the warm sun heats the surface layers of a lake.  This water becomes less dense due to its heating, and "floats" on the colder, denser waters below.  Three layers of water are thus set up.  The surface warm waters are called the epilimnion, the middle zone of rapid transition in temperatures is called the thermocline, and the cold bottom waters, usually around 39 F (temperature of maximum density), are termed the hypolimnion.  As summer progresses, the lowest cold layer of water (hypolimnion) becomes more and more isolated from the upper layers because it is colder and denser than surface waters (see Fig. 1 for documentation of this process over the seasons).



Figure 1.  Depiction of the water temperature relationships in a typical 60-ft deep lake over the seasons.  Note the blue from top to bottom during the fall turnover (this also occurs in the spring) and the red yellow and green (epilimnion, thermocline, and hypolimnion) that forms (stratification) during summer months.  Adapted from NALMS.


When cooler weather returns in the fall, the warm upper waters (epilimnion) cool to about 39 F, and because water at this temperature is densest (heaviest), it begins to sink slowly to the bottom.  This causes the lake to "turnover" or mix (blue part on right of Fig. 1), and the temperature becomes a uniform 39 F top to bottom.  Other chemical variables, such as dissolved oxygen, ammonia, etc. are also uniformly distributed throughout the lake.

As winter approaches, surface water cools even more.  Because water is most dense at 39 F, the deep portions of the lake "fill" with this "heavy water".  Water colder than 39 F is actually lighter and floats on the more dense water below, until it freezes at 32 F and seals the lake.  During winter decomposition on the bottom can warm bottom temperatures slightly.

In spring when the ice melts and surface water warms from 32 to 39 F, seasonal winds will mix the lake again (spring overturn), thus completing the yearly cycle.  This represents a typical cycle, and many variations can exist, depending on the lake shape, size, depth, and location.  Summer stratification is usually the most critical period in the cycle, since the hypolimnion may go anoxic (without oxygen--discussed next).  We always try to schedule our sampling during this period of the year.  Another critical time exists during late winter as oxygen can be depleted from the entire water column in certain lakes under conditions of prolonged snow cover.


Dissolved Oxygen


This dissolved gas is one of the most significant chemical substances in natural waters.  It regulates the activity of the living aquatic community and serves as an indicator of lake conditions.  Dissolved oxygen is measured using an YSI, dissolved oxygen-temperature meter or the Winkler method with the azide modification.  Fixed samples are titrated with PAO (phenol arsene oxide) and results are expressed in mg/L (ppm) of oxygen, which can range normally from 0 to about 14 mg/L.  Water samples for this and all other chemical determinations are collected using a device called a Kemmerer water sampler, which can be lowered to any desired depth and like the Ekman grab sampler, tripped using a messenger (weight) on a calibrated line.  The messenger causes the cylinder to seal and the desired water sample is then removed after the Kemmerer is brought to the surface.  Most oxygen in water is the result of the photosynthetic activities of plants, the algae and aquatic macrophytes.  Some enters water through diffusion from air.  Animals use this oxygen while giving off carbon dioxide during respiration.  The interrelationships between these two communities determine the amount of productivity that occurs and the degree of eutrophication (lake aging) that exists.

A series of dissolved oxygen determinations can tell us a great deal about a lake, especially in summer.  In many lakes in this area of Michigan, a summer stratification or stagnation period occurs (See previous thermal stratification discussion).  This layering causes isolation of three water masses because of temperature-density relationships already discussed (see Fig. 2 for demonstration of this process).




Figure 2.  Dissolved oxygen stratification pattern over a season in a typical, eutrophic, 60-ft deep lake.  Note the blue area on the bottom of the lake which depicts anoxia (no dissolved oxygen present) during summer and the red section in the fall turnover period (there is another in the spring) when the dissolved oxygen is the same from top to bottom.  Adapted from NALMS.


In the spring turnover period dissolved oxygen concentrations are at saturation values from top to bottom (see red area which is the same in the spring – Fig. 2).  However, in these lakes by July or August some or all of the dissolved oxygen in the bottom layer is lost (used up by bacteria) to the decomposition process occurring in the bottom sediments (blue area in Fig. 2).  The richer the lake, the more sediment produced and the more oxygen consumed.  Since there is no way for oxygen to get down to these layers (there is not enough light for algae to photosynthesize), the hypolimnion becomes devoid of oxygen in rich lakes.  In non-fertile (Oligotrophic) lakes there is very little decomposition, and therefore little or no dissolved oxygen depletion.  Lack of oxygen in the lower waters (hypolimnion) prevents fish from living here and also changes basic chemical reactions in and near the sediment layer (from aerobic to anaerobic).

Stratification does not occur in all lakes.  Shallow lakes are often well mixed throughout the year because of wind action.  Some lakes or reservoirs have large flow-through so stratification never gets established.

Stratified lakes will mix in the fall because of cooler weather, and the dissolved oxygen content in the entire water column will be replenished.  During winter the oxygen may again be depleted near the bottom by decomposition processes.  As noted previously, winterkill of fish results when this condition is caused by early snows and a long period of ice cover when little sunlight can penetrate into the lake water.  Thus no oxygen can be produced, and if the lake is severely eutrophic, so much decomposition occurs that all the dissolved oxygen in the lake is depleted.

In spring, with the melting of ice, oxygen is again injected into the hypolimnion during this mixing or "turnover" period.  Summer again repeats the process of stratification and bottom depletion of dissolved oxygen.

One other aspect of dissolved oxygen (DO) cycles concerns the diel or 24-hour cycle.  During the day in summer, plants photosynthesize and produce oxygen, while at night they join the animals in respiring (creating CO2) and using up oxygen.  This creates a diel cycle of high dissolved oxygen levels during the day and low levels at night.  These dissolved oxygen sags have resulted in fish kills in lakes, particularly near large aquatic macrophyte beds on some of the hottest days of the year.




The pH of most lakes in this area ranges from about 6 to 9.  The pH value (measure of the acid or alkaline nature of water) is governed by the concentration of H (hydrogen) ions which are affected by the carbonate-bicarbonate buffer system, and the dissociation of carbonic acid (H2CO3) into H + ions and bicarbonate.  During a daily cycle, pH varies as aquatic plants and algae utilize CO2 from the carbonate-bicarbonate system.  The pH will rise as a result.  During evening hours, the pH will drop due to respiratory demands (production of carbon dioxide, which is acidic).  This cycle is similar to the dissolved oxygen cycle already discussed and is caused by the same processes.  Carbon dioxide causes a rise in pH so that as plants use CO2 during the day in photosynthesis there is a drop in CO2 concentration and a rise in pH values, sometimes far above the normal 7.4 to values approaching 9.  During the night, as noted, both plants and animals respire (give off CO2), thus causing a rise in CO2 concentration and a concomitant decrease in pH toward a more acidic condition.  We use pH as an indicator of plant activity as discussed above and for detecting any possible input of pollution, which would cause deviations from expected values.  In the field, pH is measured with color comparators or a portable pH/conductivity meter and in the laboratory with a pH meter.




The amount of acid (hydrogen ion) that needs to be added to a water sample to get a sample to a pH of 4.5 (the endpoint of a methyl-orange indicator) is a measure of the buffering capacity of the water and can be quantitatively determined as mg/L or ppm as calcium carbonate (CaCO3).  This measurement is termed total alkalinity and serves as an indicator of basic productivity and as an estimate of the total carbon source available to plants.  Alkalinity is a measure of hydroxides (OH-), carbonates (CO3=) and bicarbonates present.  Plants utilize carbon dioxide from the water until that is exhausted and then begin to extract CO2 from the carbonate-bicarbonate buffer system through chemical shifts.  As discussed before, this decrease in CO2 concentrations causes great pH increases during the day and a pH drop during the night.  There are two kinds of alkalinity measured, both based on the indicators, which are used to detect the end-point of the titration.  The first is called phenolthalein alkalinity (phth) and is that amount of alkalinity obtained when the sample is titrated to a pH of 8.3.  This measurement is often 0, but can be found during the conditions previously discussed; that is, during summer days and intense photosynthesis.  Total alkalinity was noted above and includes phenolthalein alkalinity.




Like alkalinity, hardness is also a measure of an ion, though these are divalent cations, positive double charged ions like calcium (Ca++) and magnesium (Mg/L++).  Again, the units of hardness are mg/L as CaCO3.  A sample of water is buffered and then an indicator is added.  Titration to the indicator endpoint using EDTA completes the analysis.  As with all our analyses, for more detail, consult Standard Methods.  Alkalinity and hardness are complementary, so that comparing the two readings can give information about what ions are present in the system and confirm trends seen in other data.  Alkalinity and hardness are complementary because every calcium ion must have a bicarbonate ion or other such divalent negative ion and vice versa; each carbonate or hydroxide ion must have a divalent or monovalent anion associated with it.  For example, we might find high chlorides from street run-off in a particular sample.  Since chlorides are probably applied as calcium chloride (CaCl2), we would confirm our suspicions when hardness (a measure of Ca++ ions) was considerably higher than alkalinity.  If alkalinity were higher than hardness it would indicate that some positive anion like potassium (K+) was present in the lake, which was associated with the bicarbonate and carbonate ions but was not measured by hardness.  Generally speaking, high alkalinity and hardness values are associated with a greater degree of eutrophication; lakes are classified as soft, medium, or hard-water lakes based on these values.




Chlorides are unique in that they are not affected by physical or biological processes and accumulate in a lake, giving a history of past inputs of this substance.  Chlorides (Cl-) are transported into lakes from septic tank effluents and urban run-off from road salting and other sources.  Chlorides are detected by titration using mercuric nitrate and an indicator.  Results are expressed as mg/L as chloride.  The effluent from septic tanks is high in chlorides.  Dwellings around a lake having septic tanks contribute to the chloride content of the lake.  Depending upon flow-through, chlorides may accumulate in concentrations considerably higher than in natural ground water.  Likewise, urban run-off can transport chlorides from road salting operations and also bring in nutrients.  The chloride "tag" is a simple way to detect possible nutrient additions and septic tank contamination.  Ground water in this area averages 10-20 mg/L chlorides.  Values above this are indicative of possible pollution.




This element, as noted, is an important plant nutrient, which in most aquatic situations is the limiting factor in plant growth.  Thus if this nutrient can be controlled, many of the undesirable side effects of eutrophication (dense macrophyte growth and algae blooms) can be avoided.  The addition of small amounts of phosphorus (P) can trigger these massive plant growths.  Usually the other necessary elements (carbon, nitrogen, light, trace elements, etc.) are present in quantities sufficient to allow these excessive growths.  Phosphorus usually is limiting (occasionally carbon or nitrogen may be limiting).  Two forms of phosphorus are usually measured.  Total phosphorus is the total amount of P in the sample expressed as mg/L or ppm as P, and soluble P or Ortho P is that phosphorus which is dissolved in the water and "available" to plants for uptake and growth.  Both are valuable parameters useful in judging eutrophication problems.




There are various forms of the plant nutrient nitrogen, which are measured in the laboratory using complicated methods.  The most reduced form of nitrogen, ammonia (NH3), is usually formed in the sediments in the absence of dissolved oxygen and from the breakdown of proteins (organic matter).  Thus high concentrations are sometimes found on or near the bottom under stratified anoxic conditions.  Ammonia is reported as mg/L as N and is toxic in high concentrations to fish and other sensitive invertebrates, particularly under high pHs.  With turnover in the spring most ammonia is converted to nitrates (NO3=) when exposed to the oxidizing effects of oxygen.  Nitrite (NO2-) is a brief form intermediate between ammonia and nitrates, which is sometimes measured.  Nitrites are rapidly converted to nitrates when adequate dissolved oxygen is present.  Nitrate is the commonly measured nutrient in limnological studies and gives a good indication of the amount of this element available for plant growth.  Nitrates, with Total P, are useful parameters to measure in streams entering lakes to get an idea of the amount of nutrient input.  Profiles in the deepest part of the lake can give important information about succession of algae species, which usually proceeds from diatoms, to green algae to blue-green algae.   Blue-green algae (an undesirable species) can fix their own nitrogen (some members) and thus out-compete more desirable forms, when phosphorus becomes scarce in late summer.







The algae are a heterogeneous group of plants, which possess chlorophyll by which photosynthesis, the production of organic matter and oxygen using sunlight and carbon dioxide, occurs.  They are the fundamental part of the food chain leading to fish in most aquatic environments.

There are a number of different phyla, including the undesirable blue-green algae, which contain many of the forms, which cause serious problems in highly eutrophic lakes. These algae can fix their own nitrogen (a few forms cannot) and they usually have gas-filled vacuoles which allow them to float on the surface of the water.  There is usually a seasonal succession of species, which occurs depending on the dominant members of the algal population and the environmental changes, which occur.

This usual seasonal succession starts with diatoms (brown algae) in the spring and after the supply of silica, used to construct their outside shells (frustules), is exhausted, green algae take over.  When nitrogen is depleted, blue-green algae are able to fix their own and become dominant in late summer.

The types of algae found in a lake serve as good indicators of the water quality of the lake.  The algae are usually microscopic, free-floating single and multicellular organisms, which are responsible many times for the green or brownish color of water in which they are blooming.  The filamentous forms, such as Spirogyra and Cladophora are usually associated with aquatic macrophytes, but often occur in huge mats by themselves.  The last type, Chara, a green alga, looks like an aquatic macrophyte and grows on the bottom in the littoral zone, sometimes in massive beds.  It is important to understand the different plant forms and how they interact, since plants and algae compete for nutrients present and can shade one another out depending on which has the competitive advantage.  This knowledge is important in controlling them and formulating sensible management plans.  Samples are collected using a No. 20 plankton net (63-micron mesh), preserved with 10% formaldehyde and examined microscopically in the laboratory.




The aquatic plants (emergent and submersed), which are common in most aquatic environments, are the other type of primary producer in the aquatic ecosystem.  They only grow in the euphotic zone, which is usually the inshore littoral zone up to 6 ft., but in some lakes with good water clarity and with the introduced Eurasian water-milfoil (Myriophyllum spicatum), milfoil has been observed in much deeper water.  Plants are very important as habitat for insects, zooplankton, and fish, as well as their ability to produce oxygen.  Plants have a seasonal growth pattern wherein over wintering roots or seeds germinate in the spring.  Most growth occurs during early summer.  Again plants respond to high levels of nutrients by growing in huge beds.  They can extract required nutrients both from the water and the sediment.  Phosphorus is a critical nutrient for them.  The aquatic plants and algae are closely related, so that any control of one must be examined in light of what the other forms will do in response to the newly released nutrients and lack of competition.  For example, killing all macrophytes may result in massive algae blooms, which are even more difficult to control.




This group of organisms is common in most bodies of water, particularly in lakes and ponds.  They are very small creatures, usually less than 1/8 inch, and usually live in the water column where they eat detritus and algae.  Some prey on other forms.  This group is seldom seen in ponds or lakes by the casual observer of wildlife but is a very important link in the food web leading from the algae to fish.  They are usually partially transparent organisms, which have limited ability to move against currents and wave action, but are sometimes considered part of the 'plankton' because they have such little control over their movements, being dependent on wind-induced or other currents for transport.

Zooplankton is important indicators for biologists for three reasons.  First, the kind and number present can be used to predict what type of lake they live in as well as information about its stage of eutrophication.  Second, they are very important food sources for fish (especially newly hatched and young of the year fish), and third, they can be used to detect the effects of pollution or chemical insult if certain forms expected to be present are not.  These data can be added to other such data on a lake and the total picture can then lead to the correct conclusions about what has occurred in a body of water.

Zooplankton is collected by towing a No. 10 plankton net through the water and the resulting sample is preserved with 10% formaldehyde and then examined microscopically in the laboratory.  Qualitative estimates of abundance are usually given.




The group of organisms in the bottom sediments or associated with the bottom is termed benthos.  These organisms are invertebrates (lacking a backbone) and are composed of such animals as aquatic insect larvae and adults, amphipods (fairy shrimp), oligochaetes (aquatic worms), snails, and clams.  The importance of this group for fish food and as intermediates in the food chain should be emphasized.  Because of the tremendous variety of animals in each group and their respective tolerances for different environmental conditions, this group is a very important indicator of environmental quality.  One of those organisms is called Hexagenia, the large mayfly that hatches in late July and precipitates much trout fishing in our local trout streams.  This organism has a 2-yr life cycle; the larval form (naiad) lives in thick organic muds making a U-shaped burrow, so it can take in algae and detritus on which it feeds.  It requires high dissolved oxygen at all times and good water quality to survive, so when present it indicates excellent water quality is present. We examine samples from deep water stations for the presence of organisms, as certain types live in low to no dissolved oxygen conditions, whereas other kinds can only exist when their high dissolved oxygen needs are satisfied.

These benthic organisms are collected using a special sampler called an Ekman dredge or Ekman grab sampler.  It is lowered to the bottom in the open position, a messenger sent down the line and tripped.  This results in about an l square foot section of bottom being sampled.  The sample is washed through a series of screens to remove the fine mud and detritus, leaving only the larger organisms and plant material behind.  The sample is then picked in the field or lab and the organisms found identified.





The top carnivores in most aquatic ecosystems, excluding man, are the fish.  They are integrators of a vast number and variety of ever-changing conditions in a body of water.  They, unlike the zooplankton and benthos, which can reflect short-term changes, are indicative of the long-range, cumulative influences of the lake or stream on their behavior and growth.  The kind of fish, salmon or sunfish, can tell us much about how oligotrophic (low productivity) or eutrophic (high productivity) a lake is.  We collect fish with seines, gill nets and from lucky fishermen on the lake.  Most fish are weighed, measured, sexed, and their stomach contents removed and identified.   Fish are aged using scales, and breeding condition is observed and recorded.  The catches from our nets and age information on the fish will tell us how your length-at-age data compare with state averages and whether or not fish growth is good.  Another problem, "stunting", can be detected using these sources of information.

Stomach contents of fish document whether or not good sources of food are present and help confirm age and growth conclusions.  Imbalances in predator-prey relationships are a closely related problem, which we can usually ascertain by examining the data and through discussions with local fishermen.  From studying the water chemistry data and supportive biological data, we can make recommendations, such as habitat improvement, stocking of more predators, and chemical renovation.  We can also predict for example, the effects of destroying macrophytes through chemical control.  All elements of the ecosystem are intimately interrelated and must be examined to predict or solve problems in a lake.






Ryerson Lake is located in Newaygo County and is in the Muskegon River watershed.  The local watershed is composed of the land surrounding the lake which has many houses located on it.  There are lawns and large areas of grasses and shrubs and some forested areas, especially on the east side near the YMCA camp.  The houses are on septic tanks and so we are concerned about the septic tank effluent, which depending on soil type could end up seeping into the lake through groundwater.  There is also Eurasian milfoil in the lake which can expand and cover large areas of the substrate if conditions are optimal.

The local riparian zone is very important also, especially that band right at the lake (see Appendix 1 for lawn care and other recommendations). Things that can be done to inhibit entry of undesirable and deleterious substances into the lake are: planting greenbelts (thick plants that can absorb nutrients and retard direct runoff into the lake) along the lake edge, reducing erosion where ever it occurs, reducing or eliminating use of fertilizers for lawns, cutting down on road salting operations, not feeding the geese or ducks, no leaf burning near the lake, prevention of leaves and other organic matter from entering the lake, and care in household use of such substances as fertilizers, detergents to wash cars and boats, pesticides, cleaners like ammonia, and vehicle fluids, such as oil, gas, and antifreeze (summarized in Appendix 1).



Ryerson Lake is a 292-acre located near Fremont, MI.  We established two types of stations on Ryerson Lake for sampling various parameters in this study (Fig. 3-5, and Table 1, 2).  Water chemistry and zooplankton were sampled at one site (station A), while places and times for sampling fish were set up in various locations around the lake to maximize catch of fishes (Table 1).  Fishes were collected using seines at stations S1, S2, S3, and S4, gill nets at stations G1 and G2, and trap nets at stations TN1, TN2, and TN3 (Fig. 5).

Figure 3.  Google map of Ryerson Lake showing the extensive development, especially on the west side and the undeveloped watershed on the east side.




Figure 4.  Hydrographic map of Ryerson Lake showing the depth contours, distribution of various depths of water, inlets, and the outlet.  Map provided by Progressive Engineering.




Figure 5.  Map of Ryerson Lake showing the water quality 80-ft deep sampling station (A- see Table 1 for description) and fish sampling sites for seining (S1, S2, S3, S4), gill netting (GN1, GN2), and trap netting (TN1, TN2).




Table 1.  Place, time during which various gear were deployed at Ryerson Lake.  GN = gill net, TN = trap net, S = seine.

Fishing Site Time Time
Gear Name Start Finish Start Finish
GN1 East shore 1430 2020 2022 925
GN2 East shore 1416 1943 1955 900
TN1 East shore 1430 1000
TN2 West shore – S 1510 1030
TN3 West shore – N 1545 1110
S1 Marge’s Pointe 1740 1800
S2 Boat Launch Pointe 1810 1818
S3 Caretaker house 1630 1642
S4 North Creek Sandbar 1700 1709


Table 2.  Location and description of sampling stations where various water quality and biological samples were collected in Ryerson Lake, Newaygo Co., Michigan, 2013.  See Fig. 3 for map of locations and Fig. 4 for hydrographic map.


Station Letter                                     Description/Location



A                               In the northern basin, depth = 80 ft


S1                               Seining station, south end, east shore: Marge’s Pointe


S2                               Seining station south end, Boat Launch Pointe


S3                               Seining station north basin east shore; Caretakers house


S4                               Seining station north basin north shore; North Creek Sandbar


GN1                           Gill netting in south basin east shore


GN2                           Gill netting in south basin east shore


TN1                            Trap net set in south basin along the east shore


TN2                            Trap net set in the middle basin, south shore


TN3                            Trap net set in middle basin, west shore







Most eutrophic lakes we work on are shallow, but Ryerson Lake is unusual in that it has a deep hole of 80 ft (Fig. 4).  There are several other deep spots in the lake which adds to the habitat diversity, but none are 80 ft.  The littoral zone is extensive and highly vegetated.




Ryerson Lake is 209 acres and is extensively developed on the west side.



Light Penetration


The Secchi disc (measure of water transparency) readings during 24 July 2014 at station A was 2 m (6.6 ft) (Fig. 5, Table 2), which is not a particularly good reading, but it does indicate high productivity in the lake (eutrophic status).  This is a reflection of the high concentrations of nutrients measured in the lake which results in growth of algae and plants.



Temperature/Dissolved Oxygen


Water temperature is intimately associated with the dissolved oxygen profiles in a lake.  The summer profile is the one that most characterizes a lake and the stratification impacts are very important.  A lake goes through a series of changes (see introductory material- Temperature) in water temperature, from spring overturn, to summer stratification, to fall over turn, to winter conditions.  During both summer and winter rapid decomposition of sediments and detritus occurs when bottom waters are fertile and can cause degraded chemical conditions on the bottom (to be discussed).   Because the lake is essentially sealed off from the surface when it is stratified during summer, no dissolved oxygen can penetrate to the bottom and anoxia (no dissolved oxygen conditions- a dead zone) can result.  This has implications for the aquatic organisms (fish will not go there) and chemical parameters (phosphorus is released from the sediments under anoxic conditions, which then contribute these nutrients to the lake during the fall overturn).

During early summer, when we measured the temperature/oxygen profile, water temperatures were warm at the surface (24.4 C - 76 F), there was a thermocline (rapid change between warm and cool water temperatures) between 13 and 16 ft, and little or no dissolved dissolved oxygen at or below 16 ft (Table 3, Fig. 6).  This has two consequences:  it effectively makes the entire water volume below 16 ft unavailable to fish and this dead zone promotes phosphorus regeneration from the bottom sediments, which was abundantly clear from Progressive Engineering and our dataset (see water quality data – Table 4).  We measured this profile prior to maximum stratification, so we expect conditions will get much worse before summer ends.  This finding indicates the lake has some fertile mud or other organic material on the bottom of the lake, which degraded the oxygen levels. Most warm water fishes require at least 3 mg/L while cool water fish, such as northern pike and walleye require 5 mg/L.  Hence these fish will be subject to the squeeze noted in Fig. 6 : warm temperatures in surface water forces them downward, while no dissolved oxygen in the preferred bottom cool waters of the lake forces them into too warm surface waters. This point is important for fish management considerations.




Table 4.  Dissolved oxygen (mg/L) and water temperature (F) profile for station A

(80 ft) 24 July 2014 on Ryerson Lake, Newaygo County (see Fig. 3 for station location).


  (M)      C       (MG/L)
0 24.4 8.7
1 24.4 8.6
2 23.8 8.7
3 23.6 8.5
4 21.9 5
5 15.3 0.1
6 11.9 0.1
7 10 0.1
8 8.8 0
9 8.2 0
10 7.8 0
11 7.5 0
12 7.1 0
13 6.7 0
14 6.3 0
15 5.8 0
16 5.3 0
17 4.9 0
18 4.8 0
19 4.5 0
20 4.4 0
21 4.4 0
22 4.3 0
23 4.3 0
24 4.2 0
25 4.3 0







Figure 6.  Dissolved oxygen (mg/L) and water temperature (F) profile for station A, Ryerson Lake, 24 July 2014.







Figure 7.  Depiction of the dissolved oxygen concentrations in a stratified lake, showing the surface layer (epilimnion) where warmest temperatures exist, the thermocline area where water temperatures and dissolved oxygen undergo rapid changes, and the bottom layer, where the coolest water exists, but has no or very low dissolved oxygen present.  Cool water fishes, such as northern pike and walleyes are “squeezed” between these two layers and undergo thermal stress during long periods of summer stratification. 






The pH (how acid or alkaline water is) for Ryerson Lake during 24 July 2014 at station A (80 ft) showed a typical pattern matching the expected situation. The pH was highest at the surface (8.18) where algal and aquatic plant growth remove carbon dioxide and increase pH, while it is lowest on the bottom (7.98) where decomposition of bottom sediments increases the CO2 produced and reduces pH (Table 4).


Table 4.  Conductivity (uSiemens), pH, chlorides (CL), nitrates (NO3), ammonia (NH3), and soluble reactive phosphorus (SRP) for Ryerson Lake, 24 July 2014.  See Table 2, Fig. 5 for location of station A.  All concentrations are in mg/L.

Surface 8.18 585 12 0.5      <0.02    <0.005
12 M 8.07 384 12 0.22 0.0987 0.0144
23 M 7.98 437 14 0.59 0.7606 0.1605





Chloride concentrations in Ryerson Lake were surprisingly low ranging from 12 to 14 mg/L (Table 4), which is one of the lowest chloride concentrations we have measured in a lake. Chloride ions are conservative ions, which mean they are not altered by biological or chemical activity; they can only change with evaporation or input of water of differing concentrations of chlorides.  They can derive from septic tank effluent, road salt runoff, or can be naturally occurring.  Therefore they accumulate in a lake and give a good impression of the past history of inputs of that ion, as well as co-occurring substances from runoff, such as nutrients, toxic substances, and sediment. This low a concentration indicates almost pristine conditions with no suggestion of septic tank or road salt runoff.   Part of the reason for these low values may be input from the inlet streams, which may be dominated by rainwater which has low chloride concentrations.




We are interested in phosphorus (P) because P is generally the limiting nutrient for plant growth and the level of concentrations can indicate the trophic state or amount of enrichment in the lake.  Soluble reactive phosphorus (SRP) measures only that P which is dissolved in the water, which is the form that is readily available for algal and plant growth.  Total P would be all the P in the water, dissolved and that tied up in algae or other detritus.  During summer, SRP values were at trace levels (<0.005 mg/L) in the surface sample, because algae and aquatic plants take up all the phosphorus for growth (Table 4). Phosphorus is probably limiting in surface waters at this time in Ryerson Lake.  At mid depth (ca. 40 ft) the SRP was 0.01 mg/L which is fairly low as well.  The bottom sample however contained 0.16 mg/L which is very high and indicative of decomposition processes producing phosphorus and ammonia, as well as other toxic substances, such as carbon dioxide.  These findings are fairly typical of a eutrophic lake and are corroborated by a much larger and long term dataset of Progressive Engineering.  For example during summer 2013, they found total phosphorus which is different than SRP and probably a bit higher, to be 0.69 mg/L on the bottom in the deep spot.

We concluded two things from these data: first, P is limiting in the lakes in surface waters during summer and will stop growth of algae and plants until more phosphorus enters the lake (limiting nutrient).  One way for that to happen is excessive water skiing in the lake, which can stir up bottom sediments, resulting in the release of phosphorus and promotion of algal growth.  SRP could come in from the inlets, septic tank flow into groundwater and by lawn fertilization.    Second, it confirms the finding that the bottom waters are inhospitable to fish during summer stratification.  Residents need to do all they can to prevent nutrients from entering the lake so as to preserve the current water quality they do enjoy.  See Appendix 1 for suggestions.




Nitrate is very important since it too is a critical plant nutrient as well as P; however, blue-green algae can generate their own nitrogen, favoring them when nitrate concentrations are depleted.  Nitrates in Ryerson Lake during 24 July 2014 ranged from 0.22 at the surface to 0.59 mg/L on the bottom (Table 4).  We usually see trace concentrations of nitrates in the surface waters as we observed with SRP, so it appears that there is inadequate P but excess nitrates.





Ammonia is also a plant nutrient, but it can be toxic to fish in high concentrations, which is exactly what we observed on the bottom during summer 24 July, since we found trace amounts in surface waters (expected since most ammonia is converted to nitrates) (Table 4).  At mid depths ammonia levels were 0.1 mg/L, but on the bottom we measured 0.76 mg/L, which would be toxic to fish, if the lack of dissolved oxygen would not kill the fish first.  Ammonia is formed by the decomposition of bottom sediments under low or no oxygen present.



Hydrogen Sulfide


Hydrogen sulfide is a toxic substance produced under conditions of no dissolved oxygen (anoxia) from the decomposition of organic matter on the bottom.  It is the rotten-egg smelling chemical; it was zero on the bottom on 24 July, which was unexpected with the lack of dissolved oxygen measured.




Conductivity is a measure of the ability of water to conduct current and is proportional to the dissolved solutes present.  During our early summer survey, conductivity ranged from 384 to 585 uS (Table 4).  There did not appear to be any pattern with depth.  These are moderately low values, compared to other lakes, partially explained by the low chlorides.







            We did not sample algae in Ryerson Lake, but wanted to ensure that residents be on the lookout for an exotic species, called starry stonewort (Picture 2), which has been observed in many Michigan lakes in the past few years.  Note this species is an alga, and is a very destructive plant.  It looks a lot like Chara, another green alga but is somewhat different.  If seen, it should be reported to the board and follow up studies done to confirm identification and begin treatment before it reaches nuisance levels.





Picture  4.  Starry stonewort



Aquatic Macrophytes


Ryerson Lake was populated with many species of macrophytes based on observations during the 2014 study. They are a very important component of the lake ecosystem serving several functions.  They are shelter and nurseries for young fish, they are spawning substrates for some species (e.g., minnows), they produce many insects which are important food for fishes, and help to retard wave action from producing and re-suspending sediments from wave action.    Those aquatic plants (not an exclusive list) include one invasive species: Eurasian milfoil (Myriophyllum spicatum) and several native species including: lily pads Nymphaea, cattails Typha, bulrushes Scirpus, eel grass Valliseneria, and thin-leafed naiads Naijas spp. We also found the alga Chara, which looks a lot like an aquatic macrophyte.






Zooplankters are small invertebrates present in most lakes and ponds (See Picture 3 for an example of a copepod).  They are critical connectors between plants (they eat algae) and fish, since they are important as food for larval fish and other small fishes in the lake and are indicators of the amount of predation that fish  exert on these organisms.  Zooplankton we collected (Table 5) was comprised of very few species (five), indicating that there was not a diverse group of these organisms in Ryerson Lake.  These species included: Daphnia (see Picture 4), Mesocyclops, Sida crysalina, Skistodiaptomus oregonensis, and Chydorus.  The two dominant groups were Daphnia (45% by number) and Skistodiaptomus oregonensis (also 45%), which has two implications.  First, one of the things we look for is the presence of the large species of zooplankton: Daphnia especially. Daphnia is slow, energy-rich, large, and an easy target for fishes.  Therefore, since we found large quantities of these large zooplankters present in the lake it indicates that at least during summer fish predation is not intense, as is often seen in lakes dominated with planktivores (zooplankton eaters), such as small bluegills, yellow perch, and black crappies.  Our fish sampling confirmed that there were moderate numbers of small bluegills present, but they were confined to the near shore zone in the aquatic plants, and apparently did not go offshore into the open water during our sampling in July.

Second, Daphnia is more efficient than copepods (a smaller, faster group of zooplankton – Skistodiaptomus orgegonensis is an example and was abundant) at filtering algae from the water column.  Since Daphnia were so abundant, they are helping to control algae in the surface waters.  Copepods are also not fed on as often by fish since they are faster, unless other large zooplankters are rare.

Lastly, Chaoborus, an insect larva called phantom midges in the Diptera (fly) family was also present in the zooplankton samples in large numbers.  This is an intriguing finding, since it is known that these larvae are not present in lakes with dissolved oxygen present in bottom waters during summer since they are eaten by fish.  The fact that they are so abundant in our zooplankton tow shows that these organisms, which can live in anoxic conditions, were present and moving up and down in the water column during this period.  They will be subject to predation when the lake overturns in the fall.



Table 5.  A listing of the abundance (% composition based on counting a random sample of 100 organisms) of zooplankton species (see Picture 3-4) collected from station A in Ryerson Lake,  2014 (see Fig. 5 for station locations).  Chaoborus are insects in the family Diptera (flies) called phantom midges.  They are usually eaten quickly by fish, but can survive in lakes with no dissolved oxygen in the bottom waters, which is the case here.

Group Abundance
Daphnia spp.  45%
Chydorus spp. Rare
Sida chrysallina Rare
Mesocyclops edax Rare
Skistodiaptomus oregonensis  45%
Many Chaoborus present



Picture 3.   A copepod (zooplankter).



Picture 4.  Daphnia, a large zooplankter, adept at eating algae.





Fish Species Diversity


We collected fish using three trap nets (stations TN1, TN2, TN3) (Fig. 5, see Picture 5) with some of the resulting fish shown in Picture 6.  A 50-ft seine (stations S1, S2, S3, S4 – Fig. 5, Picture 7), and two gill nets (shown as stations GN1 and GN2 – Fig. 5, Picture 8) were also deployed in the lake. The nets were used during the daytime on 24 July 2014 (see Table 1 for times); the gill nets were picked up and reset, while the trap nets were left overnight.  Seining with a 50-ft seine was done at four sites on the lake in different habitats.  Most fish were released; we kept enough for an adequate sample for ageing and diet analyses.   We never want to kill too many fish, especially top predators, as they are so important to fish community balance in a lake.  We could have used a few more large fish (especially largemouth bass), but the ones we did catch and those that were donated by fishers provided a fairly good sample for some basic information on the lake.


The lake has a high diversity of fish species, some of which were stocked (walleye); most were native.  We collected 19 species in our sampling efforts in July (Table 6) plus common carp Cyprinus carpio which were reported to us as being in the lake.  There appears to be a huge year class of northern pike in the lake, since we collected and were given many fish in the 19-24-inch range.  The high abundance of northern pike has prompted MDNR to expand fishing opportunities for this species in the lake, which is justified based on how many we caught and the slow growth rate measured.  In addition there are three other important top predators in the lake:  largemouth bass, black crappie, and walleye.  In addition, rock bass and yellow perch also are predaceous at larger sizes and act as top predators, along with yellow and brown bullheads and yellow perch (large adults).  It appears from what we know about northern pike and walleyes and our diet information, that northern pike are having a depressing effect on yellow perch in your lake, since they are a preferred prey item, if not enough soft-rayed fishes (minnows) of sufficient size are available.  Our sampling also reflected a dearth of larger yellow perch which would also be expected. It was surprising to us that walleyes can even survive in the lake, with the degraded water quality environment in which they are forced to live during summer, but since they are present during the whole year, and because the lake is so productive, they probably will grow well during the cooler periods of the year.

In addition to a good suite of top predators, the lake also contains a good population of bluegills and black crappies.  A few green sunfish and pumpkinseeds were also documented.  As noted, yellow perch sizes appear to be truncated; there were many young of the year (YOY) indicating excellent reproduction (same for largemouth bass), but few yellow perch appear to be making it to larger sizes, undoubtedly due to northern pike and walleye predation with some contribution by largemouth bass as well.  There are a few rock bass and we found two species (brown and yellow) bullheads in the lake.  There were also seven species of minnows captured: emerald, bluntnose, spotfin, golden, mimic, blacknose, and blackchin shiners.  Overall this is an excellent diversity of predators and prey.

It appears that there is adequate spawning substrate for yellow perch and largemouth bass (sandy gravel areas) and a diversity of habitats that support the high number of other species of minnows which also seem to have adequate populations.  The northern pike situation is interesting.  It appears there was an outstanding year class formed probably 3-5 years ago which resulted in the lake being overrun with northern pike.  This infers that there is or can be great spawning somewhere in the lake, mostly likely the four inlets and outlet creeks, when conditions are optimal (high water or flooding?).  Since we did not find any or few other small pike nor any huge ones (there are reports of a few in the lake), it indicates that there was poor recruitment in other years.  Usually one should see a large number of hammer-handle pike (juveniles) in years with successful reproduction, which fisherman would report and we would sample.

Lastly, we noted two species of larval mayflies (Hexagenia and Baetidae) and caddisflies in the diet items eaten by various sunfish.  This is a good indication of the high water quality of the lake, since these aquatic insects can only survive in areas with high dissolved oxygen over at least 1 year as well as appropriate substrate and water temperatures.


Picture 5.  One of the trap nets used at station TN-1 (Fig. 5, Table 1) Ryerson Lake, 24-25 July 2014.




Picture 6.  Fishes captured in Ryerson Lake, 24 July 2014.



Picture 7. Deployment of the 50-ft seine in the near shore zone.


Picture 8.  Experimental gill net with fish being brought into the boat.

Table 6.  List of the code, common name, and scientific names of the fishes collected during a 24-25 July 2014 survey of Ryerson Lake.

Table 6.  Fish code, common name, and scientific name of the fishes collected from

Ryerson Lake, 24-25 July.



Code Taxon Scientific Name
BC BLACK CRAPPIE Pomoxis nigromaculata
ND BLACKCHIN SHINER Notropis heterodon
NH BLACKNOSE SHINER Notropis heterolepis
BG BLUEGILL Lepomis macrochirus
BM BLUNTNOSE MINNOW Pimphalus notatus
SV BROOK SILVERSIDES Labidesthes sicculus
BN BROWN BULLHEAD Amerius nebulosus
ES EMERALD SHINER Notropis athernoides
GL GOLDEN SHINER Notemigonus crysoleucas
GN GREEN SUNFISH Lepomis cyanellus
LB LARGEMOUTH BASS Micropterus salmoides
MC MIMIC SHINER Notropis volucellus
PS PUMPKINSEED Lepomis gibbosus
RB ROCK BASS Ambloplites ruprestis
SF SPOTFIN SHINER Cyprinella spiloptera
WL WALLEYE Sander vitreus
YB YELLOW BULLHEAD Amerius natalis
YP YELLOW PERCH Perca flavescens

*Common carp Cyprinus carpio were reported in the lake by sports fishers.



Fish Diets


The diet of bluegills was almost exclusively insects with the addition of some algae (Chara) (Table 7).  Fish caught ranged in size from 1.1 to 8.5 inches.  The smaller 2-5-inch group ate insects, including mayflies, caddisflies, chironomids (fly larvae), snails, amphipods, and some Chara.  Bigger fish (6-8.5 in) fed on a similar group of organisms, including chironomids, caddisflies, dragonflies, terrestrial insects, and most importantly the larval form (naiad) of the large mayfly Hexagenia.  It is important to document Hexagenia present in the diets, since it indicates they must be present in the lake and they are excellent fish food as well.   Hexagenia is an indicator of high water quality as well as very high energy fish food.  In many other lakes I work on, at this time of the year, the bluegills are struggling to find food and often I see these fish eating only algae and aquatic plants, which does not get them much energy.  Hence, I expect their populations are doing well in the lake.



Table 7.  Listing of the species collected, length, weight, sex, and diet information for fishes from Ryerson Lake, Newaygo County, MI 24-25 July 2014.  NA = not available, ZOOP = zooplankton, M = male, F= female, 1= poorly developed gonads. I = immature, MT = empty stomach, CHIR = Chironomidae, MT = empty stomach, xx = unknown.  See Table 6 for a definition of fish species codes.


Total Weight
Gear Date Species len (in) (Oz.) Sex Diet
S2 24-25 JULY BC 1.4 0.02 II NA
S3 24-25 JULY BC 1.7 0.02 II NA
S3 24-25 JULY BC 2.0 0.05 II MT
S3 24-25 JULY BC 2.0 0.06 II NA
S2 24-25 JULY BC 2.1 0.06 II NA
S2 24-25 JULY BC 2.2 0.07 II NA
S2 24-25 JULY BC 2.2 0.09 II NA
S3 24-25 JULY BC 2.3 0.08 II MT
S2 24-25 JULY BC 2.3 0.08 II NA
S2 24-25 JULY BC 2.3 0.08 II NA
S3 24-25 JULY BC 3.6 0.3 II MT
TN3 24-25 JULY BC 4.1 0.5 II II
TN3 24-25 JULY BC 4.2 0.5 II II
TN3 24-25 JULY BC 4.3 0.6 II II
TN2 24-25 JULY BC 7.0 3 II ODONATA
TN1 24-25 JULY BC 8.9 6.3 M1 BG 48 MM
GN1 24-25 JULY BC 11.2 12.6 F5 XX FISH
TN1 24-25 JULY BC 11.9 13.5 F5 MT
TN1 24-25 JULY BC 11.9 15 F5 MT
S3 24-25 JULY BG 1.1 0.01 II NA
S2 24-25 JULY BG 1.2 0.02 II NA
S2 24-25 JULY BG 2.5 0.1 F1 MT
S2 24-25 JULY BG 4.0 0.6 F1 MT
S2 24-25 JULY BG 4.1 0.6 F1 MT
GN1 24-25 JULY BG 5.3 1.5 II II
GN1 24-25 JULY BG 5.4 1.6 F1 F1
GN1 24-25 JULY BG 5.7 2.0 F1 F1
S4 24-25 JULY BG 6.3 2.8 M3 MT
S1 24-25 JULY BG 6.4 2.8 M3 MT
S1 24-25 JULY BG 6.5 3.4 M3 MT
GN1 24-25 JULY BG 6.5 2.9 F3 F3
S1 24-25 JULY BG 6.6 3.7 M3 MT
S1 24-25 JULY BG 6.7 4.1 M3 MT
S1 24-25 JULY BG 7.1 4.3 M3 CHARA
S1 24-25 JULY BG 7.5 4.4 M3 MT
S1 24-25 JULY BG 8.5 8.4 M3 MT
S3 24-25 JULY BM 1.2 0.01
S3 24-25 JULY BM 1.5 0.01
S3 24-25 JULY BM 1.8 0.02
S3 24-25 JULY BM 2.0 0.04
S3 24-25 JULY BM 2.7 0.1
S3 24-25 JULY BM 3.0 0.1
TN1 24-25 JULY BN 13.3 22.4 F5 BG 108 MM
S3 24-25 JULY ES 1.7 0.02
S3 24-25 JULY ES 1.7 0.02
S3 24-25 JULY ES 1.8 0.02
S3 24-25 JULY ES 1.8 0.02
S3 24-25 JULY ES 1.8 0.02
S3 24-25 JULY ES 1.9 0.03
S3 24-25 JULY ES 1.9 0.03
S3 24-25 JULY ES 2.0 0.04
S3 24-25 JULY ES 2.1 0.03
S3 24-25 JULY ES 2.1 0.03
S3 24-25 JULY ES 2.4 0.05
S3 24-25 JULY ES 2.4 0.06
S3 24-25 JULY ES 2.7 0.07
S4 24-25 JULY GL 4.7 0.6 CC NA
S2 24-25 JULY GN 3.7 0.5 F3 MT
S3 24-25 JULY LB 1.3 0.01 II NA
S2 24-25 JULY LB 1.3 0.01 II NA
S3 24-25 JULY LB 1.3 0.02 II NA
S1 24-25 JULY LB 1.4 0.02
S1 24-25 JULY LB 1.5 0.02
S1 24-25 JULY LB 1.5 0.03
S1 24-25 JULY LB 1.5 0.04
S1 24-25 JULY LB 1.6 0.02
S1 24-25 JULY LB 1.6 0.03
S1 24-25 JULY LB 1.6 0.03
S3 24-25 JULY LB 1.6 0.03 II NA
S1 24-25 JULY LB 1.7 0.03
S1 24-25 JULY LB 1.7 0.05
S1 24-25 JULY LB 1.7 0.04
S1 24-25 JULY LB 1.7 0.03
S1 24-25 JULY LB 1.7 0.04
S1 24-25 JULY LB 1.7 0.04
S3 24-25 JULY LB 1.7 0.04 II NA
S3 24-25 JULY LB 1.7 0.03 II NA
S3 24-25 JULY LB 1.8 0.04 II NA
S1 24-25 JULY LB 2.1 0.1
S1 24-25 JULY LB 2.1 0.1
S1 24-25 JULY LB 2.2 0.1
S1 24-25 JULY LB 2.4 0.1
S1 24-25 JULY LB 4.1 0.5 II 2 XX FISH (MINNOWS?)
S2 24-25 JULY LB 4.8 0.8 II LB 45 MM
S3 24-25 JULY LB 4.9 0.9 F1 MT
S3 24-25 JULY LB 4.9 0.9 II MT
S3 24-25 JULY LB 5.4 1.3 F1 2 LB 47, 43 MM
S3 24-25 JULY LB 5.4 1.2 II LB 54 MM
S3 24-25 JULY LB 5.5 1.3 F1 LB 48 MM
S3 24-25 JULY LB 5.5 1.3 II LB 35 MM
S4 24-25 JULY LB 5.7 1.6 CC MT
GN1 24-25 JULY LB 5.8 NA II MT
S4 24-25 JULY LB 5.9 1.6 F1 LB 46 MM
S2 24-25 JULY LB 6.2 2.0 F1 3 XX FISH , 1 YP 45 MM
S3 24-25 JULY LB 6.4 2.0 F1 MT
S4 24-25 JULY LB 9.4 6.4 F1 XX FISH
GN2 24-25 JULY LB 10.5 NA F1 MT
GN2 24-25 JULY LB 11.6 NA F1 MT
GN2 24-25 JULY LB 11.8 NA F1 XX FISH
GN2 24-25 JULY LB 12.0 NA F1 MT
GN1 24-25 JULY LB 12.0 15.9 F1 XX FISH - 2
GN2 24-25 JULY LB 12.4 NA M1 XX FISH
GN2 24-25 JULY LB 12.5 NA M1 BG 1.8, 1.3 IN
S3 24-25 JULY MC 1.9 0.04
S3 24-25 JULY MC 1.8 0.03
S3 24-25 JULY MC 1.7 0.02
S3 24-25 JULY MC 1.8 0.03
S3 24-25 JULY MC 1.7 0.02
S3 24-25 JULY MC 1.8 0.03
S3 24-25 JULY MC 1.6 0.03
S3 24-25 JULY MC 2.0 0.04
S3 24-25 JULY MC 2.0 0.04
S3 24-25 JULY MC 1.7 0.03
S3 24-25 JULY MC 1.7 0.02
SC 16-Jun NP 13.0 NA NA MT
SC 17-Jun NP 14.0 NA NA MT
SC NO DATE NP 14.7 10.3 F1 NA
SC 21-Jun NP 15.0 NA NA MT
SC 16-Jun NP 15.0 NA NA MT
GN1 24-25 JULY NP 15.4 11.1 M1 LB 55 MM
GN1 24-25 JULY NP 15.6 13.3 F1 YP 90 MM
SC 17-Jun NP 16.0 NA NA MT
SC 16-Jun NP 16.0 NA NA ?YP 105 MM
SC NO DATE NP 16.5 14 F1 NA
GN1 24-25 JULY NP 16.5 NA F1 MT
GN2 24-25 JULY NP 16.8 NA F1 NA
SC 21-Jun NP 17.0 NA NA MT
SC 17-Jun NP 18.0 NA NA MT
GN2 24-25 JULY NP 18.2 NA F1 MT
GN1 24-25 JULY NP 18.3 19.1 F1 XX FISH
SC 16-Jun NP 19.0 NA NA YP 115 MM
GN1 24-25 JULY NP 19.1 NA M1 MT
GN1 24-25 JULY NP 19.9 23.8 M1 MT
SC 17-Jun NP 20.0 NA NA MT
GN2 24-25 JULY NP 20.9 27.8 F1 MT
GN2 24-25 JULY NP 20.9 24 M1 MT
GN2 24-25 JULY NP 21.6 NA F1 BG 4.87 IN
GN1 24-25 JULY NP 21.7 NA F1 MT
GN1 24-25 JULY NP 22.4 NA F1 MT
SC 7-Jan NP 24.0 NA NA LB 125 MM, GL 113 MM
SC 16-Jan NP 25.0 NA NA BG 72, 75 MM
SC 24-May NP NA NA NA YP 65 MM
S2 24-25 JULY PS 3.2 0.3 F1 MT
S2 24-25 JULY PS 4.2 0.8 F1 ALGAE
S4 24-25 JULY PS 4.2 0.8 F1 MT
S2 24-25 JULY PS 4.6 1.2 M1 MT
S3 24-25 JULY PS 4.7 1.3 M2 MT
S3 24-25 JULY PS 4.8 1.5 M2 CADDISFLIES
GN1 24-25 JULY PS 5.2 1.8 F3 F3
S2 24-25 JULY RB 1.3 0.03 II NA
GN1 24-25 JULY RB 8.5 8.2 M1 MT
TN2 24-25 JULY RB 8.5 8.2 M1 MT
GN1 24-25 JULY RB 10.5 14.6 F5 LARGE CRAYFISH 0.7 OZ
S3 24-25 JULY SF 1.3 0.05
S3 24-25 JULY SF 1.6 0.02
S3 24-25 JULY SF 1.6 0.02
S3 24-25 JULY SF 1.8 0.03
S3 24-25 JULY SF 2.0 0.04
S3 24-25 JULY SF 2.0 0.04
S3 24-25 JULY SF 2.0 0.04
S3 24-25 JULY SF 2.2 0.05
S3 24-25 JULY SV 1.6000 0.01 NA NA
S3 24-25 JULY SV 1.7 0.01 NA NA
S2 24-25 JULY SV 1.3 0.01 NA NA
GN1 24-25 JULY WL 10.8 6 F1 XX FISH
GN1 24-25 JULY WL 11.9 7.8 F1 MT
GN2 24-25 JULY WL 12.0 8 F1 MT
GN1 24-25 JULY WL 12.4 9.6 F1 MT
GN2 24-25 JULY WL 23.3 63.5 F5 MT
TN2 24-25 JULY YB 8.1 5 F1 CRAYFISH
S4 24-25 JULY YP 2.1 0.05 II NA
S3 24-25 JULY YP 2.2 0.06 II NA
S3 24-25 JULY YP 2.4 0.08 II NA
S3 24-25 JULY YP 4.2 0.4 M1 MT
S3 24-25 JULY YP 4.3 0.4 F1 MT
TN3 24-25 JULY YP 4.7 0.6 F1 F1
S4 24-25 JULY YP 5.8 1.2 F1 MT
GN1 24-25 JULY YP 5.9 1.2 F1 F1
S4 24-25 JULY YP 5.9 1.2 F1 MT
S4 24-25 JULY YP 6.3 1.5 F1 MT
S4 24-25 JULY YP 6.3 1.5 F1 MT
S4 24-25 JULY YP 6.5 1.7 F1 MT
S4 24-25 JULY YP 6.7 2.0 F1 MT



Three other species of sunfish we collected included the green sunfish, pumpkinseed, and rock bass. We only caught one green sunfish and it had an empty stomach (Table 7).  Pumpkinseeds are much more abundant, since we caught 13 that ranged from 3.2 to 5.6 inches (Table 7).  Pumpkinseeds are ecologically adapted to eat mollusks and we did observe some snails in their diet.  They mostly ate insects and one ate algae.  The insects included: chironomids, amphipods, mayflies, caddisflies, and snails.  Like bluegills, one ate the large mayfly Hexagenia, further confirmation that this large food item is present in Ryerson Lake.  Rock bass appear to be uncommon in Ryerson Lake, but they are an important predator at large sizes.  We collected four fish from 1.3 to 10.3 inches and the largest one was eating crayfish, which is a common prey item for this species.  They also eat fish.

Largemouth bass appear to be quite common in the lake and we collected fish ranging from 1.3 to 12.5 inches (Table 7).  We always have difficulty catching larger individuals, since they do not appear in trap nets and do not gill very well.  There seems to be great spawning substrate (gravel and sand) both for bluegills and largemouth bass, which build and guard nests during spring-early summer.  There was ample evidence of many young-of-the-year (YOY), since they were common to abundant in the seine hauls (Table 7).  YOY bass from 1.8 to 2.9 inches were eating zooplankton, amphipods (Hyalella – sometimes called skuds), and an adult dragonfly.  Like bluegills, there is an excellent and diverse benthic fauna present for bass (and bluegills as we have already seen) in the littoral zone, available to promote good growth of the small sizes of largemouth bass.

Largemouth bass from 4.1 to 12.5 inches switched from eating zooplankton and insects to being predators on fish as they grew older; some of them were cannibalistic as well, consuming some of the abundant YOY bass present in the environment (Table 7).  Others ate bluegills and minnows.  This is excellent information, since it indicates that largemouth bass are consuming bluegills and minnows and that these prey items are apparently plentiful enough in the lake to sustain the intense predation largemouth bass can exert on prey populations in a lake, which also includes their own young.

The most abundant predator we collected in Ryerson Lake was the northern pike.  We collected many in gill nets and obtained many more from sports fishers.  All together we examined 31 northern pike that ranged from 13 to 26 inches (Table 7).  As expected they were exclusively fish eaters, having consumed a number of prey species, including: one golden shiner (4.4 in), two largemouth bass (2.1-4.9 in), four yellow perch (2.6-4.5 in), and three bluegills (2.8-4.9 in).  All prey except golden shiners were YOY fishes.  Obviously this shows how important northern pike are in maintaining balance in the fish population by consuming smaller fishes.  It also shows one possible reason for why yellow perch are uncommon in the lake.

Walleye is another top predator and some have been stocked into Ryerson Lake in the past.  We collected five walleyes that ranged in length from 10.8 to 23.3 inches (Table 7).  One had eaten an unknown fish, but walleyes are known predators on bottom-dwelling fishes and with their specialized eyes do most of their feeding at night or under low-light conditions.  They would be another predator that would target yellow perch, contributing to their low abundance in the lake.  The fact that we caught five fish in the gill nets we set is an indication that there are quite a few residing in the lake.  The fact that they survived, despite the considerable stresses experienced during summer stratification (fish squeeze (Fig. 7) : no dissolved oxygen in required cool bottom waters, while too warm temperatures in oxygenated surface waters) is somewhat surprising.  Northern pike are also cool-water species like walleyes and also grow poorly and suffer stress during the warmer periods of the year.

Black crappies were collected in modest numbers in our sampling efforts (we saved 22 for analyses).   Those 1.5 to 5.1 inches were eating zooplankton, which is common for this species (Table 7).  Those from 7 to 11.9 inches were eating dragonflies and fishes (bluegill and unknown species).  This is an important predator in the lake and will help to control the abundant bluegill populations.

Another species that appears to be rare in the lake, but might be more abundant than is indicated from our sampling efforts, was the brown and yellow bullheads.  We collected one each of these fish.  The brown bullhead was eating a 4.3-inch bluegill and was a large individual (13.3 inches) (Table 7).  The yellow bullhead was smaller, 8.1 inch and was eating a crayfish.

Yellow perch appear to be uncommon in Ryerson Lake, based on the data we collected and reports of the local fisher people.  We only caught 15 in our nets (mostly YOY and juveniles in our seine), and gill nets are extremely efficient at catching yellow perch. The yellow perch we obtained ranged from 2 to 6.7 inches and were eating zooplankton and insects (mayflies and caddisflies) (Table 7).    Yellow perch usually are common in the presence of largemouth bass, since their habitats do not overlap precisely; largemouth tend to be shallow, while yellow perch adults anyway, tend to be out deeper.  Northern pike, however, are voracious predators on yellow perch, and we see a similar pattern (low abundance) as was observed in Ryerson Lake, in lakes where northern pike are common.  This situation is exacerbated in Ryerson Lake, since there are a great abundance of northern pike present.   Presence of moderate numbers of walleyes contribute to the diminution of yellow perch as well.  The low abundance of yellow perch is unfortunate, since they are great fish to catch and provide outstanding table fare.


The panfish community in the lake is comprised of bluegills, green sunfish, pumpkinseeds, rock bass, and largemouth bass, all members of the sunfish family.  This complex is the backbone of any warm-water lake fish community and is usually self-sustaining, since the largemouth bass have adequate spawning substrate (gravel and sandy shores) and can usually control the panfish and prevent stunting.  The high diversity of prey is being consumed by the bluegills, black crappies, rock bass, and small largemouth bass along with help from bullheads, yellow perch, so it appears that a considerable amount of your prey resources are being efficiently converted into fishable biomass.

We also collected an amazing seven species of cyprinids (minnow family) in our nets.  These included the following species:   Mimic shiner, bluntnose minnow, blackchin shiner, blacknose shiner, emerald shiner, spotfin shiner, and the golden shiner.  The golden shiner is a particularly important minnow, since they are omnivorous eating zooplankton, insects, detritus, and algae and grow to large sizes providing excellent prey for the larger predators in the lake, which can often have a limitation on the number of large prey they require as they grow bigger.  Minnow species are an excellent addition to the fish fauna, since they utilize resources that none of the other fish consume (algae and detritus and probably some insects) and they add an important forage fish for top predators, such as yellow perch, northern pike, and largemouth bass.  These species contribute to the high species diversity we noted in the fish community, which is important for maintaining stability under the different stressors of the environment and varying population swings of the predators in the lake.    The analogy to a diverse stock portfolio is apt here. The large mayfly Hexagenia was found in stomachs of bluegill and pumpkinseed in Ryerson Lake during 2014.  The water quality in the near shore zone must be adequate to support them (high dissolved oxygen), despite the lack of dissolved oxygen in the deep area during summer stratification.  The other requirement that apparently is satisfied is to have soft, thick organic substrate where they can make U-shaped burrows and filter the water of detritus and algae.

Lastly, there is another common species that is probably confused with minnows in the lake called the brook silversides.  They have a 2-year life cycle, grow up to 2-3 inches, and can be seen feeding at the surface, sometimes jumping out of the water when they are chased by predators.  Again this is another good member of the fish community adding another prey species to the wide diversity in the lake.

We were told that common carp are also present in the lake.  This is a destructive species and should be killed or removed if caught or shot by archers.  The predators we documented will probably eat large numbers of their young, but adults should be targeted by humans by any legal means possible to reduce their numbers.



Mercury in fish


As noted, mercury is a problem in most of Michigan’s inland lakes.  Most mercury comes to the watersheds of lakes through deposition from the air with most coming from power plants burning coal.  The elemental mercury is converted to methyl mercury through bacterial action or in the guts of invertebrates and animals that ingest it.  It becomes rapidly bioaccumulated in the food chain, especially in top predators.  The older fishes, those that are less fatty, or those high on the food chain will carry the highest levels.  Studies we have done in Michigan lakes and studies by the MDNR have shown that large bluegills, largemouth bass, black crappies, northern pike, and walleyes all contain high levels of mercury.  This suggests that fishers should consult the Michigan fishing guide for recommendations on consumption, limit their consumption of large individuals, and try to eat the smaller ones.  It also suggests that a trophy fishery be established for largemouth bass, and some of the larger individual bluegills in the lake.



 Fish Growth


Growth of the fishes we collected was determined by ageing a sample of fish of various sizes using multiple scales and comparing the age of fish from Ryerson Lake with Michigan DNR standards (Latta 1958, DNR pamphlet no. 56).  Bluegills are common in Ryerson Lake and those we aged (n=21) were growing at or slightly above state mean lengths (Table 8, Fig. 9).  The fish we aged ranged from 1.1 to 8.5 inches, so there is a good size range of fish present, suggesting a well balanced population in control by the large numbers of predators in the lake.  The scattered aquatic plant beds present in the lake, the good diversity and abundance of benthos, and abundance of large zooplankton are apparently providing food and good habitat for bluegill shelter and sufficient food for adequate growth.



Table 8.  Growth of selected fishes collected from the Ryerson Lake, Newaygo Co., 14 July 2014 and some fishes from later in the year provided by fishers.  Fishes were collected in seines, gill nets, and trap nets, scales removed, aged, and total lengths at various ages compared with Michigan state mean lengths for various fishes at those same ages (see Latta 1958).  Shown is the age (years) of the fish, its total length (inches) based on MDNR state of Michigan mean lengths, and the mean length-at-age of Ryerson Lake fishes along with sample size (N) in parentheses.  See Figs. 8-14 for graphical display of these same data.

Age (yr)             Len (in) Len (in)  
Species              MDNR Ryerson Lake  

0 2.1 1.1(2)
1 2.9
2 4.3 3.9(3)
3 5.5 5.3(4)
4 6.5 6.4(9)
5 7.3 7.1(1)
6 7.8 7.5(1)
7 8 8.5(1)
8 8.5
9 8.5
10 9.2
0 3.3 1.8(9)
1 6.1 5.3(8)
2 8.7 10.8(4)
3 10 11.1(5)
4 12.1 12.2(3)
5 13.7
6 15.1 16.5(1)
7 16.1 18(1)
8 17.7
9 17.9
1 3.2 3.7(1)
2 3.7
3 4.5
4 5
5 5.1
6 5.8
7 4.3
0 2
1 2.9 3.7(2)
2 4.1 4.3(3)
3 4.9 4.8(3)
4 5.7 5.4(3)
5 6.2
6 6.8
7 7.3
8 7.8
0 3.3 2.2(4)
1 4 3.9(1)
2 5.7
3 6.8 6.2(7)
4 7.8
5 8.7
6 9.7
7 10.5
8 11.3
9 11.7
0 2.3(6)
1 4.5(3)
2 5.9 7(1)
3 8
4 9
5 9.9 8.9(1)
6 10.7
7 11.3 11.7(3)
8 11.6
0 7.9
1 15.5 14.3(4)
2 19.4
3 22.2 17(1)
4 23.9 18.2(3)
5 25.4 22.2(6)
6 27.7
7 32.5
8 37.1
9 34.8
10 44.4
0 1.5 1.3(1)
1 3.2
2 4.3
3 5.2
4 6.2
5 7.3
6 7.9
7 8.8 8.5(2)
8 9 10.5(1)
9 9.9
10 10.5
0 6.6
1 9.1 11.9(1)
2 12 12.2(2)
3 15.9
4 17.8
5 18.9
6 18.8
7 18.8 23.3(1)
8 21.4
9 19.7
10 22.6













Figure 8. Growth of bluegill in Ryerson Lake (red squares) compared with the Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.


Largemouth bass were also common in Ryerson Lake, especially YOY, but we never saw very many very large fish.  Fish collected ranged from 1.3 to 18 inches (Table 7).  The age-length relationship for Ryerson Lake bass (Fig. 9) was mostly similar to the growth rates of Michigan DNR’s fish, so there do not appear to be any growth issues with your fish.  This species is one of the keystone predators in your lake and responsible for keeping the bluegills in check, so the big fish should be left in the lake to the degree possible.  Those foul hooked should of course be kept.  The other reason, as noted elsewhere, is that large individuals are probably contaminated with mercury and should not be eaten anyway.  We concluded the following:  first, they are generally growing at state averages, and second, based on our findings of large numbers of young-of-the-year fish caught (personal observations; Table 7), we think that largemouth bass are reproducing adequately in the lakes. We explored the near shore zone in the lake, and there definitely was considerable gravel/sand bottom along shore that is good spawning substrate for the sunfish family members, including largemouth bass.



Figure 9. Growth of largemouth bass in Ryerson Lake (red squares) compared with Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.


Yellow perch seem to be scarce in the lake based on our collections and fishers reports. Those we did catch ranged from 2 to 6.7 inches (N=15) seemed to be growing at or above Michigan DNR averages (Table 8, Fig. 10).  Yellow perch are important prey fish that are usually not too susceptible to bass predation, and are outstanding table fare for people.  Hence, we would like to have seen more of them in the lake.




Figure 10. Growth of yellow perch in Ryerson Lake (red squares) compared with the Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.


We do not think stocking yellow perch would contribute much to increasing the population with the abundance of predators currently inhabiting the lake.


The one green sunfish we collected was growing slightly above state averages.  This fish was a 3.7 – inch YOY (Table 8, Fig. 11).




Figure 11. Growth of green sunfish in Ryerson Lake (red squares) compared with the Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.



Figure 12. Growth of pupkinseeds in Ryerson Lake (red squares) compared with Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.

We analyzed 13 pumpkinseeds from collections; these fish ranged from 3.2 to 5.6 inches (Table 8, Fig. 12).  They also grew approximately at MDNR state averages for this species.

Apparently a number of walleyes have been stocked into Ryerson Lake.  As we have previously noted, we believe this is an activity that runs contrary to fish management principles for three reasons:  first, walleyes are not native to this population and are not expected to reproduce, second, stocking is only acceptable under a number of conditions that must be clearly documented.  This includes a situation where the species is native and some catastrophe reduces numbers to very low levels and stocking can assist recovery of the species.  In some cases we have seen stunted bluegill populations reduce the number of largemouth bass surviving by eating eggs and larvae from nests.  Winterkill can also eliminate susceptible species and re stocking may be the only alternative to restore populations.  Third, Ryerson Lake is a classical example of a eutrophic lake which puts the squeeze (see Fig. 7) on cool water species, such as walleye and also northern pike.  These species require cool water with high dissolved oxygen.  These conditions are met in Ryerson Lake during fall, winter, and early spring.  However, during summer stratification, water warms in surface waters to unacceptable levels, while the cool water required for survival is devoid of or has low dissolved oxygen concentrations.  During this time cool water species are stressed, some probably die, and growth is restricted until other times of the year.

We captured five walleyes that ranged from 10.8 to 23.3 inches (Table 8, Fig. 13). These fish appeared to be growing at state average levels.


Figure 13. Growth of walleyes in Ryerson Lake (red squares) compared with Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.

Northern pike appear to be the most abundant fish predator in Ryerson Lake.  We collected a number in our nets and many were provided by sport fisherman.  In all, 28 fish were collected and 14 were aged; fish ranged from 13 to 26 inches (Table 8, Fig. 14).  Most of the fish were 3-5 years old, were growing below state averages, and because they were so abundant, are probably consuming many prey fish from the community.  Apparently, the years 2009-2011 were good years for the survival of northern pike.  Since we caught no small northern pike (<13 inches) in seines or gill nets, nor were they given to us by fishers, it appears that a good year class was not produced in the last 3 years.  We suspect that during 2009-2011 conditions were optimal for spawning.  We also suspect that most spawning probably occurs in the four inlet streams and perhaps the outlet.  More attention should be paid to finding out if there are northern pike runs in these streams and whether there are marshes which can act as nurseries and in which northern pike are growing and then enter the lake.  Obviously, the slow growth confirms our suspicions that cool water fishes are being stressed and that along with the inflated population of northern pike has led to slower growth than state averages.  The MDNR allowed increased limits are justified by our data.


Figure 14. Growth of northern pike in Ryerson Lake (red squares) compared with the Michigan state averages (blue diamonds) (see Latta 1958), 24 July 2014. See Table 8 for raw data.


Fish management Recommendations

Fish management strategies emanating from these data include the following.  First, we suggest that the abundant northern pike population be reduced, hence the increased limit recommended by MDNR is supported.

Second, we recommend catch and release of the bigger largemouth bass, say those > 15 inches, so they can control the prey fish population. We always encourage people to put back large predators to maintain good fish community balance (in this case with the exception of northern pike).  This allows the larger, mature predators to spawn successfully, promotes good growth of bluegills and prevents fish stunting in the lake, and they are probably contaminated with high concentrations of mercury any way (see Mercury in Fish for a discussion).

Third, as we pointed out, walleyes are stressed in Ryerson Lake during summer stratification by too warm water at the surface and no dissolved oxygen on the bottom where cooler waters reside (see the Fish Squeeze – Fig. 7).  This results in poor growth and probably some fish die as a result.  In addition, as pointed out stocking walleyes into Ryerson Lake violates at least four principles of fishery science:  1.  The fish is not native and most likely will not spawn, 2.  The existing fish community is a co – evolved warm-water fish community and should not be de-stabilized by introduction of another keystone predator, 3.  Water quality conditions, warm surface water and no dissolved oxygen in cool bottom waters, are not conducive nor optimal for a cool water fish, 4.  You are playing ecological roulette with stocking, since you could introduce diseases (VHS see below), parasites, or non-indigenous species through stocking of fish, especially if done by non-professionals.  We therefore recommend against stocking any more walleyes into Ryerson Lake and suggest if fishers want walleyes (they are difficult to catch anyway) they go to Saginaw Bay or Lake Erie where a world-class fishery exists.  Despite these concerns, it is obvious that some stocked walleyes did survive in Ryerson Lake.  Not knowing how many were originally stocked, we have no indication of what the survival rate was.  If a majority of fishers still want to stock walleyes, despite all these warnings, they should be obtained from a reputable source, few should be stocked, and obviously they should be stocked during the cooler periods of the year, spring or fall.  The cautionary tale I experienced in another lake was the elimination of a cool-water species called lake herring or cisco which co habited the lake with northern pike.  Despite my recommendations to the contrary a large number of walleyes were stocked and because of the “squeeze” noted above, the northern pike, walleyes, and ciscos all co occurred in a narrow band of water during summer, apparently resulting in the complete elimination of this prey species, the cisco.

Fourth, there was good spawning by the sunfish family, yellow perch, and by northern pike some years back.  Hence, because of the favorable substrate (sand and gravel) for sunfish spawning, there is no need for stocking any of these species.

Fifth, live bait use (minnows, crayfish) should be discouraged or banned because of the threat of introduction of exotic species (e.g., goldfish) and VHS (viral hemorrhagic septicemia) which killed many muskies and other species in many lakes, including Lake St. Clair.  As noted above, any stocking should be done with a guarantee from the stocker that the fish are VHS-free.  Any stocking by individuals should be banned for this very reason: introduction of fish from other water bodies may bring in parasites and diseases, including VHS, that could have a devastating effect on the fish community of Ryerson Lake.



To summarize, Ryerson Lake is a eutrophic lake with a very deep area in the center of the northern end of the lake. That deep area during summer stratification generates an anoxic, dead zone near bottom devoid of dissolved oxygen and this zone generates products of decomposition, including high concentrations of nutrients (soluble reactive phosphorus and ammonia) as well as carbon dioxide rendering this area off limits to fishes. Interestingly, chlorides, an indicator of septic tank leakage and road salt runoff was extremely low, a sign of good water quality in the lake.  Unfortunately, the buildup of nutrients on the bottom contributes to the eutrophication (nutrient enrichment) in the lake each year after spring and fall turnover, fueling algae and the extensive macrophyte beds that ring the littoral zone.  Riparians also contribute to the lakes enrichment through fertilization and septic tank seepage into the ground water.  To reduce the footprint of residents, no lawn fertilization should be done, but if necessary only nitrogen-based fertilizer should be used.  Septic tanks should be pumped at least once every 2 year.  See Appendix 1 for other suggestions to reduce nutrient input.   The remainder of the lake has variable depths, while the littoral zone is shallow with extensive plant beds, including lily pads, bulrushes, and submerged aquatic plants.  The bottom has extensive areas of sand and gravel which act as good spawning substrate for sunfish, especially largemouth bass.  Our zooplankton (small invertebrates in the water column) sample showed that a large species, Daphnia, composed over 50% of the zooplankton present in the sample. This indicates that there is probably reduced predation on the zooplankton over the deep hole, since lakes with an abundance of planktivores, such as small, stunted bluegills, usually consume most of the Daphnia present, leaving only smaller species. This effect would probably not be seen in the near shore zone because of the abundance of planktivores there. Among the benthos, insects and mussels that inhabit the bottom sediments, we found that the large mayfly Hexagenia was present.  This information was based on the appearance of this mayfly’s naiad in diets of black crappies and bluegills.  The fact this mayfly is present indicates that Ryerson Lake is a high water quality lake with adequate dissolved throughout the year, probably in the near shore zone where there is abundant organic sediments.

We collected 19 species of fishes and another, the common carp, avoided being collected but is reported present in the lake.  This is excellent biodiversity.  Members of the sunfish family (Centrachidae) dominated the species collected, while other predators included northern pike which were the most numerous predator collected and walleyes, which apparently were stocked into the lake. Whether they migrated from the Muskegon River is unknown and improbable.  In addition, there were seven species of minnows also found in the lake, including golden shiners, which are highly favored because they grow to large sizes (up 8 inches) providing forage for some of the larger predators.  Ryerson Lake also had brook silversides present, completing a diverse fish fauna.  We believe the high diversity is due to the high diversity of habitats: varying depths, near shore zone with abundant vegetation, but also some areas of gravel and sand, four inlets and one outlet, and the prey food supply, zooplankton and benthos, appears to be sufficient to feed the diversity of small fishes present, without eliminating the Daphnia from the zooplankton community.  The diets of fishes reflected the species, life stage, and feeding strategy of the fish.  Small fishes were feeding on zooplankton and benthos, while the large specimens of predaceous fishes were feeding on fishes and sometimes crayfishes.  They ate a wide variety of forage, including the young of yellow perch, largemouth bass, sunfish, brook silversides, and minnows.  In fact we believe that the feeding of the abundant northern pike along with walleye predation is probably having a depressing effect on yellow perch survival, since they appeared to be uncommon in the lake.  Growth of the fishes we examined generally was at MDNR state averages for a given age, with the exception of northern pike, which appeared to be growing below state averages.  We think this may be related to the stress that northern pike (and walleye) undergo during the summer “squeeze” (Fig. 7) stratification period and the unusually high abundance of this predator in the lake.


From the data we collected we recommend the following suggestions.  First, reduce nutrient input to the lake by reducing or eliminating lawn fertilization, clean septic tanks at least once/2 yr.  Second, we concur with the expanded limits for northern pike sanctioned by MDNR.  Northern pike appear to be abundant and are growing slowly.  Third, catch-and-release of large largemouth bass (>15 inches) is recommended so they can continue to control the bluegill population and they are probably contaminated with mercury anyway. Fourth, you should consider banning bait from outside the lake (live fish, crayfish) from being used by fishers.  Fifth, we are worried about viral hemorrhagic septicemia (VHS)-infected bait and introduction of other non-indigenous species, such as quagga mussels or VHS, coming into the lake from outside sources.  These introductions should be prevented by careful examination of boats, SCUBA gear, or bait coming from infested lakes or rivers.   Lastly, we cannot recommend any further stocking of walleyes into the lake, especially by lake residents who might inadvertently introduce VHS into the lake. We discussed the reasons for this: 1. Walleyes are not native species, 2. The lake has a co evolved fish community that has been in existence for thousands of years and is not out of balance, 3. There is a potential for introduction of VHS with stocked fish, and 4. The fish will be severely stressed during summer due to the “squeeze” of warm surface water and cool preferred bottom water that is devoid of dissolved oxygen during the summer stratification.  If the board still wants to stock fish, be sure to use a certified VHS-free source, do not stock large numbers, and stock them at large sizes (at least >8 inches during spring or fall.






Recommendations are summarized more concisely below:



1.        Nutrient inputs


Nutrients are entering Ryerson Lake and being regenerated by anoxic sediments. They also enter the lake from the following sources:

  1. Septic tanks: they seep into the groundwater through permeable sand.  They must be cleaned out often, at least once every 2 yr.
  2. Sediments can generate nutrients near bottom during decomposition processes in winter and summer. Little can be done about this except reducing nutrients from riparians, so less organic material accumulates on the bottom.
  3. Runoff, lawn fertilization, and other activities by residents contribute nutrients: Observe suggestions in Appendix 1 – greenbelts, ban pet wastes from lawns, no leaf burning at the lake, reduce impermeable surfaces, etc.
  4. Waterfowl, such as Canadian geese need to be discouraged from visiting, nesting, or hanging around the lake eating lawns.


2.       Northern Pike


Northern pike are the most abundant predators in the lake and they appear to be growing below state averages. We concur with the MDNR increased limits.


3.      Largemouth Bass


We recommend catch and release for all largemouth bass > 15 inches, unless fish are foul hooked and would die.  They help control stunting in sunfish populations.


4.      Yellow perch


Yellow perch are not very abundant, but there were quite a few young in the near shore zone.  Many top predators fed on them, so not much can be done except reducing the northern pike population.


5.      Walleye


Walleye have been stocked into Ryerson Lake.  Amazingly many have survived, providing a small fishery.  We oppose further stocking, because they are not native, they are difficult to catch, they will not spawn, stocking may introduce diseases, and most importantly, they will be severely stressed during summer stratification.


6.      Prevent Exotic Species from Entering Ryerson Lake


Prevent exotic species, besides Eurasion milfoil which has already been introduced, from entering the lake.  Consider banning bait from outside the lake to avoid the introduction of more exotic species, such as quagga mussels and VHS.  Fishers and skiers need to dry out boats and gear that come from other lakes that might be contaminated with exotic species, such as zebra mussels.


Table 9. A compilation of the various physical, chemical, and biological measures for Ryerson Lake and a qualitative assessment (good, bad, no problem) in general.    + = positive, 0 = as expected, - = negative.  “See guidelines” refers to Appendix 1 – guidelines for lake residents to reduce nutrient input into the lake.  C @ R = catch and release, DO=dissolved oxygen.


Condition            Qualitative

Documented        assessment       Problem Potential                         Action to Take




Water Clarity          0                       Moderate turbidity               Reduce nutrients

Water Depth          +                       Sediment buildup                Reduce nutrients

Water Temp.          0                     Warms up in summer            None now

Sediments              +                           Gravel, sandy, organic            None



pH                           0                                  None                                   None

Dissolved oxygen    -                   Reduced DO on bottom    Monitor, reduce nutrients

Chlorides                +                                  None                                   None

Nitrates                    -                    Buildup in lake bottom  See Guidelines; reduce N&P

Ammonia                  -                     Buildup on bottom       See Guidelines; reduce P

SRPhosphorus         -                       Buildup on bottom         See Guidelines; reduce P

Hydrogen sulfide   +                        Not present in July                      Monitor




Macrophytes            -                          Eurasian milfoil         Monitor; Treat if it expands

Zooplankton           +                         Daphnia present                          None

Benthos                  +                        Hexagenia present                        None


Largemouth bass +               Plenty YOY; few big adults                  C @ R

Bluegill               +                               Adequate               Maintain predator balance

Yellow perch       -                               Few seen                        Reduce n. pike

Minnows            +                               Abundant                             Monitor

Northern pike    +-                               Abundant                      Reduce numbers

Walleye               -                                Stocked                      No more stocking








I want to profusely thank Charles Yonkers for invaluable assistance with the lake sampling, provisions of food and lodging, access and captaining his boat, expertise in choosing sites for net deployment, arranging for fish samples, and most importantly congeniality.  Despite the curse of the banana, we successfully completed all the work required for a comprehensive survey of the lake.  I want to thank Don Clark for initial contact and making sure we got the required assistance for the lake work.  I thank my able-bodied assistants James Hart and Kim Bourke for their enthusiasm, observations, and help with the sampling.  Jason Jude provided help with some of the figures.  I appreciate the referral and water quality data provided by Paul Hausler and Tony Groves of Progressive Engineering.





Latta, William C.  1958.  Age and growth of fish in Michigan.  Michigan Department of Natural Resources, Fish Division Pamphlet no. 26. Lansing, MI.




Appendix 1.  Guidelines for Lake Dwellers; some may not apply.


  1. DROP THE USE OF "HIGH PHOSPHATE' DETERGENTS.             Use low phosphate detergents or switch back to soft water & soap.  Nutrients, including phosphates, are the chief cause of accelerated aging of lakes and result in algae and aquatic plant growth.


  1. USE LESS DISWASHER DETERGENT THAN RECOMMENDED (TRY HALF). Experiment with using less laundry detergent.


  1. STOP FERTILIZING, especially near the lake. Do not use fertilizers with any phosphate in them; use only a nitrogen-based fertilizer.  In other areas use as little liquid fertilizer as possible; instead use the granular or pellet inorganic type.  Do not burn leaves near the lake.


  1. STOP USING PERSISTENT PESTICIDES, ESPECIALLY DDT, CHLORDANE, AND LINDANE. Some of these are now banned because of their detrimental effects on wildlife.  Insect spraying near lakes should not be done, or at best with great caution, giving wind direction and approved pesticides first consideration.


  1. PUT IN SEWERS IF POSSIBLE. During heavy rainfall with ground saturated with water, sewage will overflow the surface of the soil and into the lake or into the ground water and then into the lake.


  1. MONITOR EXISTING SEPTIC SYSTEMS. Service tanks every other year to collect and remove scum and sludge to prevent clogging of the drain field soil and to allow less fertilizers to enter the groundwater and then into the lake.


  1. LEAVE THE SHORELINE IN ITS NATURAL STATE; PLANT GREEN BELTS. Do not fertilize lawns down to the water's edge.  The natural vegetation will help to prevent erosion, remove some nutrients from runoff, and be less expensive to maintain.  Greenbelts should be put in to retard runoff directly to the lake.


  1. CONTROL EROSION. Plant vegetation immediately after construction and guard against any debris from the construction reaching the lake.




  1. STOP LITTER. Litter on ice in winter will end up in the water or on the beach in the spring. Remove debris from your area of the lake.




  1. DO NOT FEED THE GEESE. Goose droppings are rich in nutrients and bacteria.


From:   Inland Lakes Reference Handbook, Inland Lakes Shoreline Project, Huron River Watershed Council.