The 2002 Fish Survey of Dunham Lake

Introduction

Dunham Lake is an exceptionally fine natural lake in a unique setting. The lake is located on the border of Livingston County (Hartland Township) and Oakland County (Highland Township), in T3N R6-7E Sections 13, 24, 18, and19. The setting is unique for southern Michigan because only a few houses are visible from the center of the lake, rolling hills and woods form the scenic backdrop, and motors are prohibited. The lake is beautiful and tranquil. In the 1950s, a 600-acre bird sanctuary was converted to real estate development with a 100-200 foot green belt around most of the shoreline (George 1984). This exceptional foresight is attributed to the planning of Murray Van Wagoner, a civil engineer and former Michigan governor. This parcel is collectively owned and managed by the 350 residential units of the Dunham Lake Property Owners Association (DLPOA). The north shore, developed later, is not in DLPOA, and has somewhat less restrictive regulations on green belt and house visibility. Lake access is restricted to residents and guests of approximately 400 fine homes.

Alterations to the water’s edge also have been very minimal. Three small parks with swimming beaches have been established, but there are no artificial frontages with bulkheads or rock riprap.

Anglers report that fishing activity is light, most game fish are released, relatively few fish are harvested, and fishing quality is average. Fish have not been stocked in recent years.

In May 2002, a survey of the lakes’ fish and aquatic habitat was authorized and contracted by the DLPOA Board. The primary contact person was Rob Schmitt of the Fish and Water Committee. Julie Magill was also especially helpful. Fish sampling fieldwork was conducted May 22 and 23. An additional visit to the lake was made on July 8 to obtain supplemental limnological data.

Several fish-related concerns expressed by residents were addressed by the fish survey and will be discussed in this report. A controversial question was should a walleye stocking program be re-initiated. (See Table 1 for scientific names of fishes and the Encyclopedia Section and for discussion of terminology). Of concern was the apparent decline in yellow perch and the sparseness of small fish. Also of interest was if the lake still supported a unique cisco population (also called lake herring). But more generally, the charge was to update the status of all fish populations, as the last fish survey had been conducted in 1987, 14 years ago.

Concerns regarding fish were addressed by collecting basic data on all species of fish present and their relative abundance, and determining for the important sport fishes the population characteristics of maximum size, recruitment, growth, and longevity. Also, I examined relative abundance of zooplankton and aquatic plants because they are of special importance to fish habitat.

Status and trends in water quality were evaluated recently by Water Quality Investigators (2001). Consequently, I focused on sampling fish and selected habitat characteristics most relevant to fish.

A considerable amount of background information is available for Dunham Lake about fish populations and water quality. Prior surveys of fish were conducted in 1890, 1976, 1979, and 1987. Their results enable the determination of trends through time and provide a perspective on the natural variation in this dynamic ecosystem. The 1890 survey, which was quite superficial, was conducted by a crew sent out by the Michigan Fish Commission, the precursor of the Fisheries Division of the Michigan Department of Natural Resources (Michigan Fish Commission, 1890). Later surveys, by James Merna (1976, 1979, and 1987) were more thorough and were entirely supported by DLPOA. Numerous water quality surveys have been conducted also.

The Watershed

Dunham Lake rests in a deep depression left by glaciers about 10,000 years ago. It is one of the headwaters of the Shiawassee-Flint river drainage. The lake has no inlet streams. Spring water rising up within Dunham Lake feeds North Ore Creek, then Bullard Lake, Parshallville Mill Pond, Lake Shannon, the Shiawassee River, the Flint River, and ultimately Saginaw Bay of Lake Huron. There is a concrete sill in the Dunham Lake outlet, but it is no barrier to fish migration during high water. The immediate watershed of Dunham Lake has been estimated at 2589 acres (Water Quality Investigators 2001). Generally, headwater lakes with and protected watersheds are less likely to develop water quality problems than lakes in large drainage systems exposed to more human activities.

Historically, fish and other organisms from as far away as the Great Lakes had access to all upper lakes in the Flint system. But within the last century, dams at the City of Flint, Lake Shannon, and Parshallville have blocked upriver movement. Fortunately, easy access by some noxious species—such as gizzard shad and white perch—has been blocked also.

Physical and Chemical Characteristics

Dunham Lake is exceptionally deep (maximum 118 feet) for it’s size (110 acres) (Water Quality Investigators 2001). In addition, there are two other deep basins, 85 and 65 feet deep (Figure 1). Only five other lakes in southeastern Michigan exceed 100 feet in depth, and none are so small in area. The surrounding soils are mostly sandy and well drained with relatively high amounts of limestone. Consequently, the lake receives considerable inputs of ground water and has a very stable water level. Because the ground water is high in calcium carbonate, marl (calcium carbonate) precipitates out and forms the grey mud characteristic of so-called marl lakes. This gradually causes, on a geological time scale, lake shoals to become progressively shallower and lake drop offs to become more abrupt.

Dunham Lake water is classified as “hard” due to the high amount of calcium carbonate. Alkalinity ranges from 123 to 198 ppm and pH from 8.1 to 8.8 (Water Quality Investigators 2001). Marl lakes tend to be clear and of low to moderate productivity because some phosphorus (an essential and often limiting nutrient for algae and aquatic plants) is bound by the marl. This beneficially reduces the rate at which lakes become eutrophic due to man’s fertilizing effects, and also completely buffers the lake from acid rain effects. On windy days, marl particles are suspended and may reduce the transparency of the water.

Most limnologists would rank Dunham Lake’s current level of basic productivity as relatively low, borderline oligotrophic. This ranking is based on phosphorus concentration (average about 10 ppb), chlorophyll content (range 1-5 ppb), and Secchi disk transparency (range 10-15 feet) (data from Water Quality Investigators 2001). As for most lakes, the productivity of Dunham Lake is probably limited more by the input of phosphorus rather than by the input of nitrogen. Low productivity is also indicated by the rarity of rooted aquatic plants and the relatively sparse fish population.

The overall quality of water in Dunham Lake has been ranked as A (index > 90) based on a mixture of nine characteristics (Water Quality Investigators 2001)

Biological Characteristics

A modest level of primary (plant) production is essential to every lake for it forms the basis of the food chain. Algae and other plants are eaten by secondary producers, namely invertebrate animals that live in the water column (zooplankton), or on the surface of plants or in the substrate (benthos). Fish, on the next level of productivity, eat both benthos and zooplankton, but zooplankton is essential to the young of all species of fish. Crayfish, midges, and burrowing mayflies are important types of benthos and are favorite foods of older fish.

Algae

The term algae include simple plants without roots that are either suspended in the water column (phytoplankton) or attached to the surface of the bottom or other plants (periphyton). Technically, Chara is also an algae; this plant rests on the bottom, is long, branched, and becomes encrusted with lime. In most lakes, phytoplankton (measured by chlorophyll sampling) is the dominant form. In Dunham Lake, all three forms are sparse. Algae are the plants most likely to respond to cultural eutrophication caused by high levels of phosphorus and/or nitrogen that leach into the lake from septic systems, fertilizers applied to lawns, and feces of pampered geese and ducks. Dunham Lake is one of a few lakes in southern Michigan in which algae and rooted plants are so sparse that chemical plant control is not being practiced.

Zooplankton

Zooplankton was sampled on May 23 and again on July 8, 2002. Results indicated the secondary level of productivity in Dunham Lake is not favorable for good growth of rainbow trout and bluegill. The protocols of Galbraith and Schneider (2000) were used to take and analyze the sample. A Wisconsin-style plankton net (#20 mesh, 4.5-inch diameter opening) was raised from depths of 60 feet (May) or 90 feet (July) to the surface while the boat was held steady over the deepest basin. In the laboratory, sample contents were strained through a screen to sort out the larger Cladocera, which are the preferred food items for trout and large bluegill. A favorable sample will contain more than 150 Cladocera over 1.4 mm in length. The May strained sample from Dunham Lake contained only 70 small Cladocera, 1.0 to 1.2 mm in length, and many small copepods. The July strained sample contained only 140 small Cladocera, 1.0 to 1.4 mm in length.

The most likely explanation is that cisco, also zooplankton feeders, are abundant enough to depress the large Cladocera. A lack of large zooplankton can have side effects: phytoplankton is cropped less, phytoplankton becomes more abundant, and water transparency is reduced. This side effect may explain why Dunham water is not as transparent, on average, as other lakes of similarly low basic productivity.

Vegetation

Higher aquatic plants play important roles in fish ecology, both positive and negative. Rooted plants enhance the production of invertebrates and fish. Plants also shelter small fish from predators such as bass and pike. This is desirable in moderation for some small fish eventually grow into large fish. However, excessive numbers of small fish relative to the available food supply causes “stunting”, especially of bluegill, black crappie, and yellow perch. Stunted fish grow slowly and very few reach a size large enough to interest anglers. A balance is needed, and is usually achieved when higher aquatic plants cover about 30% of the littoral zone.

By that standard, Dunham Lake has too few plants and other forms of fish cover. However, sparse vegetation is much better than over-abundant vegetation from both fisheries and aesthetic perspectives. The abundance of rooted aquatic vegetation in Dunham Lake is limited by the narrow littoral zone (<15 feet deep, where light can penetrate to the bottom), exposure to wave action, bottom soil type, and low nutrient input.

No floating or emergent vegetation was observed during the fish study. Submergent vegetation was very sparse. I noted one type of milfoil (Myriophyllum alterniflorum) and two types of pondweeds (thinleaf and gramineus?). Chara, the low-growing and crusty algae mentioned earlier, was the most common plant. Also present, especially in deeper water at station G4 (Figure 1), was a moss. Moss occurs in only a few relatively pristine Michigan lakes. Notably absent were exotic and obnoxious plants such as Eurasian water milfoil and curleyleaf pondweed. On the negative side, also absent were marshes, which are important spawning habitat for northern pike.

Invertebrates

Dunham Lake contains populations of two species of good-sized native clams. They are giant floater (Pyganodon grandis) and fat mucket (Lampsilis siliquoidea). These are species most commonly found in clean, hard water Michigan lakes. Clams can be a hazard to the feet of people wading in the lake, but their presence indicates good water quality because they are sensitive to certain pollutants. As part of their life cycle, clams release small parasitic glochidia that attach to the gills of fish but are relatively harmless.

No exotic zebra mussels were observed, and care should be taken to prevent their introduction into Dunham Lake. Fortunately, boats that may be contaminated are rarely brought into Dunham. Clams are at great risk because zebra mussels attach to clam shells and eventually smother them. Zebra mussels have already decimated native clams in Lake St. Clair. Aside from effects on clams, zebra mussels are not likely to become very abundant and serious nuisance in Dunham Lake because most of the lake bottom is too soft for their attachment.

Another exotic mollusk, Viviparus georgianus, is well established at the south end of Dunham Lake. This is a large striped snail, native to the southern United States, which is migrating northward and has recently reached southern Michigan waters. It is not known to be harmful but may displace native snails.

Small crayfish were found in fish stomachs and may be common in the lake. This is a native species (Orconectes propinquus) and not the invasive and aggressive rusty crayfish. They are a desirable link in the food chain because they mature at a small size do not grow too large for fish to eat.

Other observations

Blue herons were observed during the survey. One map turtle was captured in a trap net.

Past Fish Management Practices

The first fish surveyors of the lake, in July 28-30, 1890, captured “herring, bluegills, bullheads, suckers and perch” (Michigan Fish Commission 1890). The fish were reported to be “ very fat but small.” Surveyors recorded a maximum depth of 110 feet with temperatures of 77ºF at the surface and 42ºF at the bottom. They recommended stocking of “lake trout, wall-eyed pike, and black bass.” These recommendations probably were not carried out. Bass were surely already present, and both bass and walleye had access to Dunham Lake via the Shiawassee River. No records of stocking by the State have been found, especially for the period 1935-2000. Some private stockings have occurred. Merna’s 1976 report mentions the stocking of walleye, adult northern pike, rainbow trout and brook trout within the last 3 years. The last fish stocking, of walleye, probably occurred in 1987.

Fish Survey Methods

Fish samples were collected May 22 and 23, 2002 at the sites shown in Figure 1. Large fish were collected with gill nets and trap nets set over one night; and small fish were captured with a seine. Six experimental gill nets, a total of 625 lineal feet of net, were set at medium and deep sites. Five of the gill nets were 100 feet long and 6 feet deep, and all nets were composed of panels with mesh of 1½, 2, 2½, 3, and 4 inches (stretched measure). Two trap net sets were made at in-shore sites. Trap nets had 50-foot leads and 3-foot x 5-foot pots of 1.5-inch stretched mesh. The seine, 20 feet long with ¼-inch mesh, was used at six widely scattered locations with firm substrates suitable for wading.

All fish were identified to species, counted (actually, numbers of minnows were estimated), and their total length was measured to 0.1 inch or to inch group (e.g., 3 = 3.0 to 3.9 inches; 4 = 4.0 to 4.9 inches; etc.). Scale samples were removed from representative northern pike, largemouth and smallmouth bass, bluegill, pumpkinseed, rock bass, cisco, and yellow perch. Some of the fish caught in gill nets were lively enough for release back into the lake; all fish caught by other methods were released in good condition. Some dead pike, rock bass, and cisco were examined to determine the food in their stomachs. The fillets of some rock bass and cisco were examined for the occurrence of parasites.

In the laboratory, impressions of the scales were made on plastic, projected with a microfiche reader, and then examined to determine age and growth rate. Growth rates were compared to the State of Michigan averages for each species (Schneider et al. 2000a). Weight of fish caught in nets was estimated from fish lengths and state average length-weight equations (Schneider et al. 2000b).

In analyzing these data, the important considerations were:

·Physical, chemical, and biological suitability of the habitat;

·Relative abundance of each species;

·Species proportions, an indicator of predator-prey balance;

·Presence of large fish, which are important to anglers;

·Presence of small fish, an indicator of recent spawning success and future fishing;

·Mortality rate, as indicated by maximum age (longevity);

·Consistent reproductive success, as indicated by presence of all age groups

(year classes) expected to be caught by the gear;

·Growth, which indicates the balance between number of fish and food supply.

Fish Survey Results

Fish Species

The family, common, and scientific names of fishes collected from Dunham Lake in the year 2002 are listed in Table 1. The list is long and diverse, indicative of the diversity and quality of habitat that the lake provides. We collected 15 species, observed two others, and another (walleye) was reliably reported as late as 2001. The lake contains a mixture of coldwater (cisco), coolwater (e.g., smallmouth and rock bass), and warmwater (e.g., largemouth bass and bluegill) species. Note that other species (such as white sucker) may be present because failure to collect fish does not prove they are absent.

Fish Abundance and Community Structure

Information on relative abundance and size distribution of collected fish are summarized in Tables 1 and 2. Detailed records of catches in gill nets, trap nets, and seine may be found in Appendices 1-3. Note that a ranking system for relative abundance was used in Table 1 because nets are selective for certain species and sizes and not others. No type of fish sampling gear gives a completely unbiased picture of the abundance and size structure of a population and the species composition of the fish community.

The fish community in Dunham Lake is unusual among southern Michigan lakes due to the relatively high presence of cisco, smallmouth bass, and rock bass (Table 2). Among the sport species, rock bass was ranked as abundant and bluegill, largemouth bass, smallmouth bass, and northern pike were ranked as common. Combined sport fish totals were satisfactory, comprising 40% of the total numbers caught and 95% of the total weight caught (Table 2).

The catch of the top sportfish predators—northern pike and bass—was higher than normal. Their combined total was 73% by weight (Table 2). As a rule of thumb, all predators should make up 20-40% of the fish community biomass for good predator-prey balance (Schneider 1981).

Rough fish (e.g., longnose gar, carp, bullheads, and sucker) are unusually rare in Dunham Lake and are not a potential problem. These species (white sucker excepted) prefer warmer water. The net catch was limited to one yellow bullhead (2%, Table 2). As a rule of thumb (Schneider 1981), rough fish may have a significant negative effect on sport fish when they exceed 50% of the fish community biomass.

Small “forage” fish were of modest overall abundance (Table 1). Small bluegill were present but were not plentiful compared to other lakes. No small yellow perch were collected, which is very unusual. Four species of minnows were found, of which two, bluntnose minnow and blacknose shiner, were abundant. Two important species usually found in area lakes, golden shiner and lake chubsucker were not captured; those species prefer greater amounts of submerged vegetation than Dunham Lake offers.

Status of Fish Populations

Bluegill

The bluegill is a key species in Michigan lakes because it is often abundant and it’s growth is usually a good indicator of overall fishing potential. In Dunham Lake, bluegills are only of moderate abundance and on average are growing rather slowly, 1.0 inch below the State of Michigan standard (Figure 2 and Table 3). However, some large bluegills are produced and the population should be considered satisfactory. The largest one we netted was 8.8 inches long (Tables 2), but anglers have reported bluegills close to 10 inches. A “good” bluegill lake (in terms of size structure, not necessarily abundance) has been defined as one producing bluegills over 8.0 inches (Schneider 1990).

In Dunham Lake, the bluegill population is constrained by the relatively small amount of warm-water habitat, low basic productivity, and lack of vegetative cover. Growth of smaller bluegill, especially, was much below the State standard. Research elsewhere has shown that small bluegill are reluctant to move offshore and out of weed beds because they would be more vulnerable to bass and pike predation in open waters.

Zooplankton sampling (see above) confirmed that bluegill food is relatively sparse even in deeper waters.

Bluegill up to age 8 were netted, which suggests the population’s mortality rate is normal and that harvest by anglers is not excessive (Table 3). However, no bluegills from the youngest age group were collected. This suggests that poor spawning or survival may have occurred in 2001. Sometimes such “weak year classes” are due to cold summer weather, but that is not a likely explanation in this case.

Bluegills have been caught in every survey of Dunham Lake since 1890 (Table 4). Compared to prior data, the bluegill population in 2002 may be slightly depressed (Table 4) and much slower growing. However, these data have been quite variable. Growth indices were -0.4 in 1976, +0.8 in 1979, +0.1 in 1987, and –1.0 in 2002.

Pumpkinseed

Based on the limited sample, common sunfish were found to be sparse but some were relatively large (up to 8.1 inches). It appears small pumpkinseeds grow as slowly as small bluegills, but large pumpkinseeds grow better than large bluegills, indicating a more favorable balance between food supply and population abundance. Pumpkinseeds have a different “ecological niche” than bluegills because they eat less zooplankton, eat more snails and other benthos, and live on the shoals most of the time. Marl lakes usually support large snail populations and good pumpkinseed populations.

Surprisingly, pumpkinseeds were not taken in Dunham Lake surveys until 1987 (Table 4). However, it is likely that the species is native to the lake because it is native to the watershed. They can be missed in surveys that use only gill nets.

Yellow perch

Only one perch, 8.0-inches long, was taken (Tables 1 and 2). That strongly suggests that perch have become sparse in Dunham Lake. Usually, gill nets and beach seines are very effective tools for sampling adult and juvenile perch. The problem is more likely to be poor survival than poor reproduction. Here, as in other lakes, many small perch may become food for predators, and even large perch are vulnerable to large predators such as pike and walleye. Perch grow well on diets of minnows and benthic invertebrates such as mayflies, and midge larvae. In some lakes, perch eat significant numbers of small bluegills during winter.

A very unusual observation was this 8.0 female perch still contained ripe eggs when captured on May 23. In most southern Michigan lakes perch spawning is completed by mid April. However, due to great depth and the cool spring, Dunham Lake surface water did not warm to 55^oF, the temperature perch prefer for spawning, until May 15.

Perch were present as far back as 1890 and are likely native to Dunham Lake (Table 4). Gill net catch data indicate perch were decidedly more abundant in the 1970s than since then.

Largemouth bass

This population has satisfactory characteristics given the limited amount of warm-water habitat available to them. Largemouth bass comprised 21% of the total catch by weight. The largest bass netted was 16.9 inches long and 7 years old (Tables 1-3). Anglers occasionally take larger sizes and fishing is considered to be satisfactory. Bass growth rate matched the State average (Figure 2 and Table 3). Bass and other predators have a large variety of food types available to them in Dunham Lake and have an advantage because prey fish have relatively few places to hide.

Historically, the numbers of largemouth bass in Dunham Lake have been approximately the same since 1976 (Table 4). (The species was likely missed by gill netting conducted in 1890.) Growth indices have varied considerably (-0.1 in 1976, +1.7 in 1979, +2.7 in 1987, and +0.1 in 2002) but that is probably normal population oscillation and sampling variation. Some improvement in bass size should have occurred after 1976 due to increases in bass minimum size limit (10 to 12 to 14 inches) and the widespread practice of catch-and-release angling, but the samples are insufficient to detect changes in population size structure.

Smallmouth bass

This population probably has satisfactory characteristics. This a is a tentative conclusion based on a sample of one fish, 14.8 inches long and 4 years old (Tables 1-3). Growth rate of this bass far exceeded the State average. Smallmouth bass comprised only 2% of the total catch by weight of fish sampled, but this may be an underestimate of their true abundance because anglers report they catch nearly as many smallmouth as largemouth. Anglers occasionally take larger sizes and bass fishing is considered to be satisfactory. Crayfish, a favorite food of smallmouth, occur in the lake, and the volume of suitable cool-water habitat should favor this species over largemouth bass.

The history of smallmouth bass in Dunham Lake is unclear. This species, like others, had access to the lake via the connecting waters prior to the construction of dams by white settlers. Yet, the presence of smallmouth bass was not reported in any of the four previous surveys (Table 4). This strongly suggests the population has increased considerably since 1987. As far as known, smallmouth bass have not been stocked and this change is natural.

Rock bass

This population is relatively abundant (7%of the net catch by weight). Because the species prefers cool waters, they find more suitable habitat in Dunham Lake than in other southern Michigan lakes. Good-sized rock bass were taken (up to 10.4 inches long) and their growth rate was above the state average (Figure 3 and Table 4).

Unfortunately, these rock bass carry a burden of parasites that, while rarely lethal to the host fish, makes them unappetizing. Two out of five fillets contained yellow grub (Clinostomum) and three out of five contained black spot (Neascus). Both parasites have complicated life cycles involving fish-eating birds such as herons. These cysts should be removed while cleaning the fish, but are harmless to man if cooked and eaten.

The stomach contents of 14 rock bass were examined to determine their diet. Nine out of 14 contained food: nine had crayfish, six had dragonfly naiads, and two had small bluegills. These types of food items are also traditional favorites of smallmouth bass and yellow perch.

Rock bass have been on the increase (Table 4). None were reported in 1890 (but were probably present) and only small catches were made in 1976 and 1979. Gill net catches increased slightly in 1987 and strongly in 2002.

Cisco

Lake herring are still present in Dunham Lake, a sign that water quality remains good. Only four ciscoes were taken, but others could have avoided the gill nets set in deep water for them. One angler reported seeing many cisco surface feeding after ice-out last spring, and confirmed their identity by catching some by hook-and-line. The cisco taken in nets ranged from 10.6 to 11.4 inches long and from age 3 to age 4 (Table 3). Their growth rate approximated the State average. Two out of three fillets contained yellow grub infestations. All three cisco had been feeding on zooplankton, as expected.

Ciscoes are surely native to Dunham Lake because some have been caught in every netting survey since 1890 (Table 4). The species was never (or rarely) stocked anywhere in Michigan. The highest catch rate (and probably abundance) occurred in 1976. The catch in 2002 has appreciably lower, but on a par with 1979. Growth indices were lower in 2002 (-0.1) than in 1976 (+0.9), 1979 (+1.8), and 1987 (+1.9). That data, plus the relatively low numbers of zooplankton present in deeper waters noted above, suggests the cisco population is still healthy.

Generally, ciscoes live in midwater where they feed primarily on zooplankton. Consequently, they are rarely caught by anglers, but will occasionally bite on small minnows. In early December, they move into a depth of 10 feet where they spawn over sparse beds of Chara. At that time they may be observed by shining floodlights into the water.

Only 153 Michigan lakes contain populations of cisco due to this species’ need for high-quality habitat (Latta 1995). As a member of the trout family, it requires a layer of cold water in mid-summer containing a relatively high amount of dissolved oxygen (DO). Definitions of this “cisco layer” vary, but the most strict is where temperature £63^oF and dissolved oxygen ³4 ppm (Latta 1995). Ciscoes are very vulnerable to the degradation of the layer by eutrophication because organic decomposition depletes the reserve of DO. This may cause cisco die-offs in mid summer.

The table below defines the summer cisco layer in Dunham Lake from 1984 to 2002 based on temperature-DO profiles (Fusilier 2001 and this study). These show a high annual variation, but no overall trend toward degradation. In summer 1989, the cisco layer became dangerously thin (5 feet) because the lake did not completely turnover (i.e., regenerate DO by mixing with air) the previous spring (Water Quality Investigators 2001). In 2002, the cisco layer deceptively appears to be thicker (50 feet) because the profile was taken earlier in the summer.

	Depth where	Depth where	Thickness of
Sample date	Temp < 63^oF	DO >4 ppm	cisco layer
September 12, 1984	>34 ft	<52 ft	18 ft
August 23, 1989	>25 ft	<30 ft	5 ft
August 7, 1995	>22 ft	<42 ft	20 ft
August 31, 2000	>27 ft	<45 ft	18 ft
July 8, 2002	>22 ft	<85 ft	50 ft

Northern pike

Pike were surprisingly abundant. Nine pike were taken that comprised 50% of the weight of all fish sampled (Table 2). That proportion may be somewhat inflated because pike are more readily caught in gill nets than bass and bluegills. The largest pike was 30.3 inches (about 6.5 pounds) and the smallest was 15.0 inches. A good mixture of age groups was represented, from age 1 to age 6 (Table 3). This suggest that successful spawning is occurring in most years even though Dunham Lake lacks the marshy habitat pike prefer. Other possible explanations are pike are making due with poor spawning habitat or are migrating into the lake via the outlet. Interestingly, a 21.7–inch female caught on May 23 still contained ripe eggs that should have been deposited 1-2 months earlier. Apparently, that pike was frustrated and was not going to spawn at all in 2002.

Pike growth rate was considerably above the Michigan average (Figure 3 and Table 3). Favorable growth can be attributed to good temperature conditions, presence of cisco, and sparse cover that makes all species of smaller fish more vulnerable to pike predation. Large pike can eat relatively large fish of all species, and excessive pike populations can significantly reduce fishing for other fishes. Cisco and yellow perch are often preferred food. We examined the stomach contents of four dead pike from Dunham Lake: three were empty and the fourth contained two 9-inch ciscoes.

Pike were not reported in the 1890 survey, and the species may not have been established in Dunham Lake until after some adults were stocked in the mid 1970s (Merna 1976). Five of those stocked adult pike were netted in 1976. Only two pike were netted in 1987, but they were ages 4 and 6, indicating that they been produced within the lake. The catch of nine pike in 2002 indicates the pike population continues to expand. The cause of the increase in pike in the last decade is unclear, but it may be aggravating the decline in yellow perch.

Walleye

No walleye were captured during this survey. However, anglers reportedly caught a few walleye as recently as 2001, so it is likely that a few more remain in Dunham Lake. Because of their very large size (circa 30 inches) these were likely remnants from the last walleye stocking (1987?). Walleye were also stocked in 1975, and nine of those survivors were taken in the 1976 survey when two years old and 13.6 inches long (Merna 1976). No walleyes were taken in 1979, 1987, and 2002 surveys, suggesting that walleyes were not able to establish a reproducing population. Dunham Lake lacks the rocky shoals or inlet rivers that walleyes require for successful spawning. However, Dunham Lake provides good habitat for walleye survival and growth because of its coolwater habitat and cisco forage base. That is confirmed by the results 1975 and 1987 stocking. The survival of walleye from 1987 to 2001 (14 years) is remarkably good. A typical life span is 10 years, but the Michigan record is held by one walleye that lived 26 or more years in Lake Gogebic.

Other species

As noted above, among the larger sized “rough” fishes common to lakes only the yellow bullhead was represented in 2002 netting results. Catches of both bullheads and suckers were much higher in 1987, but there are other years when none have been caught in sampling (Table 4).

A total of 25 species of fish have been collected from Dunham Lake since 1890 (Table 4). Rarer species, collected sporadically, may have been present in all years. Especially interesting is the catch of several emerald shiners in 2002. That species is abundant in the Great Lakes but is established in only a couple large and cool inland lakes. They are widely sold as fishing bait, and most likely some were dumped into Dunham Lake by an angler. They may reproduce in Dunham Lake and provide additional food for predators.

Analysis

Dunham Lake is the most unique and beautiful lake I have seen in southern Michigan. Because the lake has exceptional depth, it has cold and well-oxygenated water, provides diverse fish habitats, has low basic productivity, and lacks problems with excessive algae and rooted plants. It’s pristine character is well protected by the green belt and caring residents.

The relative fish productivity of Dunham Lake can be roughly estimated from the limnological and fish community data at hand (Schneider 2000). The standing crop of all fish is computed from an equation to be approximately 36 pounds/acre, or 4000 pounds for the entire lake. The potential yield to anglers is computed to be approximately 3 pounds/acre/year, or 334 pounds for the entire lake. These values are 1/3 to 1/7 of those of a typical southern Michigan lake. They quantify the reasonable expectations for the Dunham Lake fishery.

Survey results indicate the fish populations, with the exception of yellow perch, are satisfactory to good. The lake produces sport fish of quality size, but in relatively low quantity. Panfish such as bluegill and yellow perch have low amounts of invertebrate foods available, so are unable to develop large numbers. Consequently, predators that would feed on panfish are also constrained. Fortunately, ciscoes are able to use the deep midwater resources of the lake and they help support the larger predators such as northern pike and walleye.

The fish community of Dunham Lake has become a bit “top heavy” with predators in recent years. Largemouth bass have remained constant, but coolwater species—northern pike, smallmouth bass, and rock bass—have increased. Walleye are an additional complication because they too can be effective predators (Schneider and Lockwood 1997). It appears that predation in Dunham Lake is excessive on yellow perch, and to a lesser extent bluegill. Fortunately, both species are very resilient and it is likely they eventually improve. There is a subtle difference in predation effects by bass and predation effects by pike. Bass predation typically focuses on small and medium perch and bluegill and often serves to improve their growth. However, in unproductive Dunham Lake that benefit may be negated by food competition with rock bass and cisco. Pike predation typically focuses on larger sizes of panfish, thereby placing pike in competition with anglers. Lakes with the limnological characteristics of Dunham Lake typically have no pike and better populations of yellow perch (as Dunham Lake was in 1976). In lakes with more submerged vegetation, more intensive predation is needed for panfish control and pike or walleye can be of some assistance in those waters.

Some changes in Dunham Lake fish have occurred through the years but they have not been extraordinary. Fish populations in all lakes experience at least modest fluctuations. Some fluctuations are caused by fishing (cropping of the largest sizes) or habitat alteration by man, but many are due to factors beyond our control such as weather. In a chain reaction, weak and strong year classes induced by weather during spawning may cause short-term fluctuations in the composition of the fish community, in numbers of large fish, and in quality of fishing. Fortunately, strong natural resiliency allows species to recover and (usually) to return to their former abundance. A recent example is the volcanic eruption of Mount Penetubo, Philippines. It sent a cloud around the Earth in 1992 that caused a cool summer in Michigan and poor reproduction by bluegill and other fishes in many lakes (Schneider and Lockwood 1997).

Fish kills

Fish die-offs are a common occurrence in all lakes but are rarely observed because of scavengers. Sometimes mortalities occur because of a pollutant or abnormally low dissolved oxygen in winter or summer. As mentioned before, cisco are especially sensitive to low dissolved oxygen in the thermocline. However, die-offs also occur in lakes that have no apparent deficiencies and cannot be attributed to a specific cause other than “stress”. Fish, like humans, have their burden of natural diseases, parasites, and physiological breakdowns. The natural mortality rate among even adult fish is high, about 30-50% each and every year.

Walleye stocking

The proposal to stock walleye in Dunham Lake to enhance walleye fishing has pros and cons. Past experience has demonstrated that a few large, long-lived walleye can be produced. The lake has characteristics favorable to the growth and survival of large walleye, but not to walleye reproduction. Consequently, walleye would have to be stocked periodically to maintain a fishery. After stocking ceases, all walleye would disappear within about 14 years due to natural and fishing mortality, and the ecosystem would probably return to status quo.

But there are five considerations in a stocking program, all involving potential costs and benefits. First, the lake already has populations and fisheries for smallmouth bass, largemouth bass and northern pike, so walleye stocking (if too successful) would place these (smallmouth in particular) at some risk. Second, the lake already has relatively high numbers of predators, so extra walleye predation might further harm populations of yellow perch and bluegill. Third, stocked walleye fingerlings would be heavily preyed upon by bass and pike, so relatively large sizes and high numbers would have to be stocked to get some to survive. Fourth, walleye are notoriously difficult to catch, so will there be sufficient interest? Fifth, walleye are not native to Dunham Lake, so to stock them (or any other species) is a philosophical departure from maintaining a “natural” system.

A token walleye population and fishery could be established by stocking relatively large (8-10”) fingerling walleyes. That size has a better chance of avoiding hungry bass and pike and growing to a catchable size. A stocking rate of approximately 2 fingerlings/acre (220 fingerlings) every third year would be appropriate over the long term under the prevailing conditions. I predict that about 5% (11 fish) will eventually be caught by anglers. Since the fingerlings will cost at least $1 each, the cost per adult walleye caught will be approximately $20. Stocking success and impact on other fish species (especially perch and cisco) should be evaluated in 4 years. Then, stocking rate should be adjusted accordingly or discontinued.

Trout stocking

Dunham Lake supported stocked rainbow trout in the 1970s. Several large (19-inch) trout were captured in the 1976 and 1979 surveys. The option to resume stocking still exists because suitable temperature and DO characteristics are still present. However, there are two difficulties to consider. First, northern pike are more abundant now, and they would eat significant numbers of trout. Pike predation can be reduced by stocking expensive larger trout, preferably over 10 inches in length, or by reducing the numbers of northern pike, as by intensive harvesting. Second, the zooplankton in Dunham Lake is sub optimal for rainbow trout stocking success. A more predatory trout, such as the brown trout, might survive and grow better. In 1976, rumor had it that a few large brown trout of unknown origin were present. Negatives to consider are browns are more difficult for anglers to catch than rainbows, and trout are short-lived, so would require frequent restocking. In small quantities (1 trout/acre), brown or rainbow trout are not likely to seriously affect other sport fish.

Water quality

I encourage residents to zealously protect both the quality of the water and the natural populations of plants, fish, and invertebrates. The lake is a jewel among southern Michigan lakes. It is part of the heritage of the state and of generations to come. Dunham Lake is not simply a swimming pool, fishing pond, or scenic backdrop, it is an excellent natural ecosystem. On its own it can support good fish populations and fishing, in addition to aesthetic and recreational uses.

Recommendations

1. Zealously protect the lake from chemicals, and physical and biological alterations;

2. Continue to minimize nutrient loading to maintain high levels of dissolved oxygen in the cisco layer of the thermocline;

3. Generally encourage catch-and-release fishing to make fullest recreational use of the lake’s low productivity;

4. Encourage yellow perch by reducing predation and harvest of perch and increasing removal of rock bass;

5. Carefully discuss the options regarding walleye and trout stocking;

6. If DLPOA proceeds with trout stocking, encourage removal of northern pike;

7. If DLPOA proceeds with either trout or walleye stocking, evaluate rate of return to anglers, survival and growth, and effects on other species within 2-5 years;

8. Otherwise, re-evaluate status of the fish populations in 10 years or if some change in fish or habitat occurs.

References

Galbraith, M. G. and J. C. Schneider. 2000. Sampling zooplankton in lakes. Chapter 18, In Schneider, J. C. (ed.) Manual of Fisheries Survey Methods II: with periodic updates. Michigan Department of Natural Resources, Fisheries Special Report 25, Ann Arbor.

George, M. 1984. Residents fear paradise lost. Detroit Free Press, October 18. 1984.

Latta, W. C. 1995. Distribution and abundance of the lake herring (Coregonus artedi) in Michigan. Michigan Department of Natural Resources, Fisheries Research Report 2014, Ann Arbor.

Merna, J. W. 1976, 1979, and 1987. Fish survey of Dunham Lake. Unpublished reports for DLPOA.

Michigan Fish Commission. 1890. Ninth Biennial Report. Lansing.

Schneider, J. C. 1981. Fish communities in warmwater lakes. Michigan Department of Natural Resources, Fisheries Research Report 1890, Ann Arbor.

Schneider, J. C. 1990. Classifying bluegill populations from lake survey data. Michigan Department of Natural Resources, Fisheries Technical Report No. 90-10, Ann Arbor.

Schneider, J. C. 2000. Interpreting fish population and community indices. Chapter 21 In Schneider, J. C. (ed.) Manual of Fisheries Survey Methods II: with periodic updates. Michigan Department of Natural Resources, Fisheries Special Report 25, Ann Arbor.

Schneider, J. C., P. W. Laarman, and H. Gowing. 2000a. Age and growth methods and state averages. Chapter 9 In Schneider, J. C. (ed.) Manual of Fisheries Survey Methods II: with periodic updates. Michigan Department of Natural Resources, Fisheries Special Report 25, Ann Arbor.

Schneider, J. C., P. W. Laarman, and H. Gowing. 2000b. Length-weight relationships. Chapter 17 In Schneider, J. C. (ed.) Manual of Fisheries Survey Methods II: with periodic updates. Michigan Department of Natural Resources, Fisheries Special Report 25, Ann Arbor.

Schneider, J. C. and R. N. Lockwood. 1997. Experimental management of stunted bluegill lakes. Michigan Department of Natural Resources, Fisheries Research Report 2020, Ann Arbor.

Water Quality Investigators. 2001. Dunham Lake 1984-2000 water quality studies.

Encyclopedia

Algae (or Phytoplankton)-- Single cell plants that float in the water. They are the primary food for small animals such as zooplankton and benthos. Some species of algae, especially the blue-greens, form stringy clumps. Obnoxious algae “blooms” can be temporarily controlled by treatment with copper sulfate.

Alkalinity-- A measurement of the carbonate and bicarbonate compounds dissolved in water. Like the hardness test, alkalinity is a measure of mineral content and a rough indicator of productivity. An exception is very hard lakes where excess calcium carbonate ties up phosphorus. In lakes with alkalinity of approximately 125 ppm or greater, excess calcium carbonate precipitates out of the water and accumulates on the bottom in the form of marl.

Balance (of population or community)-- To maintain good fishing in a lake there must be a proper balance between numbers of predator fish (bass, pike, and walleye) and forage fish (bluegill, perch, and minnows). A lake should contain from 3 to 5 pounds of forage fish for every pound of predators.

An overabundance of forage fish (bluegills and perch) is a common occurrence in many Michigan lakes. The result is underfed and slow-growing panfish too small to interest anglers. Surprisingly, this situation (stunting) does not necessarily result in an outstanding population of fast growing pike or bass. Most stunted bluegills and perch are 4 to 6 inches long and are beyond the optimum size for forage fish.

An overabundance of predators is a rare occurrence, but leads to equally unsatisfactory fishing. In such situations pike may seldom reach a size of 20 inches. Bluegills and perch will usually persist in the lake, but may be so scarce that they will seldom be caught. They will reproduce each year and produce a crop of young fish. However, most of the young will be eaten during their first year of life. The few that do survive will grow fast and will quickly reach a large size. Consequently, the panfish population will consist of a few large fish and a crop of young with very few fish in intermediate size ranges.

The growth rate of fish is an indicator of the predator‑prey balance in a lake without actually knowing numbers or pounds of fish in the lake. When fish are extremely slow growing it usually indicates populations are out of balance or food supply is limited.

Benthos-- Invertebrate animals that live on the surface of plants or on the substrate, or within the bottom mud. Many are immature stages of aquatic insects that may spend up to 2 years in the water. Other common types are crayfish, scuds, and worms.

Chara (or perch grass)-- The generic name for a plant (multicelled algae) that grows in mats on the bottom. It is not green. It is brittle and smells musty. It forms good habitat for fish and benthos.

Food pyramid (or food chain)-- In lakes, just as on land, the most abundant organisms are plants, which produce the organic materials needed by all higher forms of life. The plants are eaten by herbivores, the herbivores by carnivores, etc. However, some material and energy is lost in the conversion between each level. The ratios between levels in this food pyramid are approximately 10:1. Thus in lakes, each 1000 pounds of plants (mostly algae) will support about 100 pounds of zooplankton, insects and other herbivores, 10 pounds of fish such as bluegill and perch, and only about 1 pound of bass or pike. This is an oversimplification because most fish feed at multiple levels at some stage in their life.

Forage fish-- Smaller fish that are eaten by larger predacious fish. Often refers to minnow species, but broadly includes small perch, bluegill, and other panfish, and even the small sizes of predators.

Growth-- As used here, gain in length or weight of individual fish expressed as average size at a given age. Elsewhere, sometimes refers to an increase in the number of fish in the population, as due to increased recruitment.

Littoral zone-- The shallow area of the lake where light penetrates to the bottom and macrophytes can grow if other conditions (such as soil type) are suitable. The depth of this zone is approximately equal to the Secchi disk reading. The zone is productive and supports diverse plant and animal species.

Longevity-- How old fish in the population become. This varies with species and with lake (for example, some walleye live over 20 years in Lake Gogebic). Generally, few panfish reach 8 years of age and few game fish reach age 10.

Macrophytes-- Multicelled plants with roots, stems, and leaves. Submerged species live under the water but tall ones such as milfoil may extend to the surface and “canopy”. Emergent species, such as bullrush, are rooted underwater but extend above the surface. Floating species, such as water lily, have large leaves designed to float on the surface. “Weeds” are any of the above which hinder recreation.

Productivity (or production)-- The capacity of water (or land) to grow plants and animals. For aquatic plants, the most important requirements are sunlight and nutrients, especially phosphorus and nitrogen. For aquatic animals, the most important requirements are food and shelter. In Michigan lakes, the weight of fish present (standing crop of biomass) varies considerably. Unproductive trout lakes in northern Michigan may produce as low as 10 pounds per acre, whereas enriched, carp-filled impoundments in southern Michigan may have 1000 pounds per acre. Typical lakes contain a total of 50-150 pound/acre of fish. See also trophic state.

Secchi disk-- A simple black and white disk 8 inches in diameter invented by an Italian named Secchi. The disk is lower into lakes on a rope until it just disappears from view. It directly measures water clarity and turbidity, and indirectly the amount of plankton in the water and the lake’s trophic state.

Stratification--Deeper lakes seasonally develop physical and chemical layers. Two physical-chemical factors that greatly influence the lives of fish are temperature and adequate amounts of dissolved oxygen. Oxygen is replenished in a lake as wind and waves mix atmospheric air with water and as living plants produce oxygen in the presence of sunlight (photosynthesis). Oxygen is consumed by respiration of fish and other animals, by decay (oxidation) of dead plants and other organic materials, and by the respiration of living plants when not exposed to sunlight. Respiration of fish is of minor consequence in comparison to respiration of living plants and decomposition of plant matter.

During winter, dissolved oxygen supply may become critical because ice seals the water from the air and the darkness caused by snow cover restricts photosynthesis. At the time of ice formation, therefore, a lake must have sufficient oxygen stored up to satisfy the demand throughout the winter. In shallow weedy lakes the demand by respiration and decay of plants often exceeds the supply, and a winterkill of fish results. In deep lakes, the large volume of water stores enough oxygen to persist throughout the winter.

During spring (and again during fall) most lakes are completely circulated by wind action. Oxygen becomes plentiful and temperature is uniform at all depths. In late spring the surface waters warm up rapidly and a thermal stratification is set up which persists throughout the summer. Three distinct layers of water are formed: (1) the upper layer (epilimnion) has a uniformly warm temperature; (2) the middle later (thermocline) is characterized by a rapid decline in temperature with increasing depth; and (3) the bottom layer (hypolimnion) has uniformly cold water. The stratification persists because the cold bottom water is heavier than the upper warm water and wind action mixes only the upper layer. Since the lower layers are cut off from the atmosphere and plants, the supply of dissolved oxygen again becomes depleted. The degree of oxygen depletion in the cold layers determines the suitability of a lake for cold-water fish such as trout and cisco.

Stocking-- Most species of fish have a tremendously high reproductive potential. Females may spawn 5,000 to 50,000 eggs annually depending on their age, size, and species. Studies back in the 1940s proved there is little or no value in stocking panfish, or any species, into lakes that already contained wild fish of the same species and had satisfactory conditions for reproduction. This does not mean that fish stocking is a thing of the past, but rather that we should stock with a definite objective in mind and a reasonable assurance that we will realize that objective. Fish may be stocked in order to introduce a new species into a body of water or for "put-and-take" fishing.

The introduction of a new species should only be attempted if the lake offers a suitable environment for the complete life cycle of the fish. The most common limiting factors to consider are spawning requirements, food supply, abundance of predators, and temperature and oxygen requirements. If any of these factors are lacking, the introduced species of fish will not persist in the lake. The original stocked fish might persist for several years and furnish some fishing, but eventually they will disappear. Their disappearance is usually credited to excessive fishing, but it is far more likely the result of a deficiency in the habitat. The effect of a new introduction on the present fish population should also be considered. Does the present population have a balanced predator-prey ratio, and will the new fish hinder or improve this ratio?

Put-and-take stocking consists of planting fish, usually of a catchable size, with no hope of establishing a resident population of the species planted. This type of planting is used when a highly desirable fish (such as trout) is wanted in a lake known to lack certain requirements for a complete life cycle of the species. The only factors to be considered in put-and-take stocking are the effect on the present population and the adequacy of the return in terms of catch from the money invested.

Put-and-grow stocking consists of planting small fish with the notion that they will be allowed time to grow before being harvested. The objective is to take advantage of the food production of the lake or stream and eventually harvest more pounds of fish than were actually stocked.

Most lake associations consider predators when planning a stocking program for their lake because they are exciting to catch and popular with anglers. Unfortunately, several of the more desirable species have very precise, and usually limited, spawning requirements. The combination of excessive fishing pressure and limited spawning often result in insufficient predation to control panfish (prey) species—especially since predators prefer soft‑rayed minnows rather than spiny-finned bluegill and perch. Below are key points about predator spawning and stocking.

Largemouth and smallmouth bass. Spawning requirements of bass are not as specific as most other predators. Largemouth prefer sand and gravel but can construct nests on plant roots. Smallmouth are more commonly found on gravel or cobble areas of larger, deeper, clearer, and colder lakes. When bass have suitable spawning conditions in a lake their natural reproduction will render any stocking program insignificant.

Tiger muskellunge. The tiger muskie is a sterile hybrid cross between northern pike and muskellunge. The use of these fish in lake management thus requires artificial propagation in a fish hatchery and perpetual stocking every 2 to 4 years. Popularity of tigers has waned, and currently few are now stocked by Michigan Department of Natural Resources fish biologists. It is difficult to find private hatcheries that can supply this fish at a reasonable cost.

Northern pike. Spawning requirements of northern pike are very specific, and without suitable spawning habitat, pike simply will not reproduce and will eventually disappear. To successfully spawn, pike require a rather extensive area of shallow marsh with grasses or emergent vegetation such as rushes or cattails. Usually, shallow water with dense aquatic weeds is not sufficient.

Walleye. The walleye is perhaps the most popular game fish in Michigan. Unfortunately, they also are rather fussy about their spawning requirements. They prefer rocky, wind-swept shoals of larger lakes and rivers with rocky bottom. Do not expect walleye to reproduce adequately in small lakes in southern Michigan. But populations maintained by stocking occasionally produce a few young. Some success has been achieved by building spawning reefs for walleyes. Walleyes are expensive to buy, and mortality is high before they reach catchable size. Consequently, the cost per fish harvested will be high. A fishery harvest of 10% of the number stocked would be considered good. Recent research has shown that walleye can be an effective predator on stunted perch and bluegill and aid in restoring community balance.

Muskellunge. The muskie is a fish of large lakes because it is a top predator. It rarely spawns in Michigan lakes for reasons poorly understood. Stocked muskie tend to survive poorly but a few would grow to large size in lakes with an abundant supply of suckers or carp. However, they can have negative effects on perch and other game fish. It would be difficult and expensive to find a source of fingerling muskie for stocking.

Recruitment-- The process of adding to the fish population (or the fishery) by means of reproduction and growth. These fish are needed to replace older fish that constantly die from natural causes or fishing. Low recruitment for several years in a row leads to declines in abundance and fishing quality and, eventually, to extinction.

Stunting-- Excess number of fish of a species in relation to food supply. Results in slow growth and a preponderance of small- to medium-size fish. See Balance.

Trophic state-- Lakes are generally divided into three trophic states based on their level of productivity. Oligotrohic lakes produce few plants and fish because they are low in nutrients or have unfavorable chemical conditions such as low pH due to acid rain. Most have very clear water. Mesotrophic lakes are moderately productive; most Michigan lakes are of that type. Eutrophic lakes are very productive, often excessively so due to nutrient additions from human sources. As lakes become older (age), they tend to accumulate nutrients and organic matter and progress towards shallowness and higher trophic states.

Winterkill-- Death of fish during winter caused by suffocation. See stratification.

Year class (or cohort)-- Fish born in a given year, e.g., 1990.

Zooplankton-- Small animals, primarily Cladocera and Copepoda, which live in the water column feeding on phytoplankton. They are very important foods for all species of small fish and also for certain large fish such as rainbow trout, bluegill, and cisco.