Jennifer Smith, the author’s sister-in-law caught and released this huge bluegill.
Bluegills are commonly found in many waters around the State of Michigan. Bluegills are not native to the Upper Peninsula, although they are in the Lower Peninsula. Historical planting spread bluegill, other sunfish, and bass across the entire state. Stunting of bluegill can be a common problem. Over the years, DNR fisheries surveys have observed important factors in lakes that yield a better size structure in their bluegill populations.
Bluegill Natural Reproduction
Bluegills are very prolific and adequate spawning habitat is present in most waters. It is common for newly introduced bluegill to a waterbody to become a self-sustaining bluegill population in the long run. With almost unlimited bluegill spawning habitat in many waters, it is common for this species to become overabundant and slow growing, resulting in a poor overall bluegill size structure.
In the Upper Peninsula, strong cold fronts are common in the late spring/early summer when bluegills are sitting on their beds. In some years, these cold fronts can result in interrupted and less successful natural reproduction in bluegill and other members of the sunfish/bass family. This is a natural limiting factor to the overpopulation of bluegill in some northern waters. As a result, the remaining bluegill will often grow at a faster rate than waters with abundant bluegill. People often assume that growth rates for all fish species are slow in northern Michigan and the Upper Peninsula.
Our DNR fisheries surveys indicate that, although slower than state-average growth rates are common for northern pike and walleye, this is not the case for bluegill and bass in UP lakes.
Predation on bluegill
Throughout my career as a fisheries management biologist, I observed some lakes where panfish, such as bluegill, were heavily preyed upon by abundant populations of northern pike, walleye, or bass. In those cases, the predator game fish, especially northern pike and walleye, kept the bluegill population so tightly under control through predation that the remaining bluegill grew quickly and eventually became large. The only way for them to survive was to get large enough to avoid predation. In my earlier career working in the UP, I caught the third-largest Master Angler bluegill that year from exactly that type of lake in the late 1970’s. That bluegill was over 12 inches long. That lake had a strong walleye and abundant pike populations. We subsequently saw larger bluegill emerging from that and other lakes like it in DNR fish surveys. It is not a secret that consulting the DNR website’s Master Angler Award database can yield trends on state waters that yield larger bluegill.
Bluegill food and lake productivity
Another lake factor we observed in our fishery surveys, which results in good bluegill growth rates and an improved size structure, is lake productivity. Marl bottom lakes often have greater lake productivity and often have above-average zooplankton populations. Bluegills typically grow well in lakes with strong zooplankton populations. In the 1960s, the Department of Conservation (precursor to DNR) established numerous two-story trout lakes, mostly stocked with rainbow trout.
The lakes where rainbow management was most successful were those with strong zooplankton populations. Eventually, trout management was lost as an option in many of those lakes as predators like northern pike became established, negating the trout plants. The two-story lakes, where bluegills were already present and trout were discontinued due to poor trout survival from predation, are good lakes to check for quality bluegill.
Summer Bluegill Feeding Pattern
A typical feeding pattern of adult bluegill schools is to suspend in deeper water and feed on concentrations of zooplankton. Bluegills also rely heavily on aquatic insect larvae, adult insects and other aquatic invertebrates.
Lightly fished bluegill waters
Of course, lightly fished bluegill lakes can produce some large bluegill, provided that the lake does not have an overabundant bluegill population. In addition, if it has one or more of the other factors discussed above that help produce better bluegill size structure, it will often lead to good results.
Some lakes are lightly fished due to poor access or they are legally private waters. While attending the University of Michigan’s School of Natural Resources, I encountered another very different situation on a bluegill lake that yielded a good-sized structure. A few of the lakes in the Huron River lake chain are heavily used by speed and sailboats and are more difficult to fish. We experienced some very good fishing by locating active bluegill on lakes that would be difficult to fish during infrequent occasions when speedboat traffic was light.
Manage for quality bluegill size structure
At the state average growth rate, it takes about 9 years for a bluegill to reach 9 inches in length. Bluegills are particularly vulnerable when the males are bedding/guarding their nests. They often spawn together in a colonial nesting area, making them easier to concentrate on once a spawning area is found.
Michigan DNR fisheries research and management biologists have struggled with how to manage some lakes for quality bluegill/panfish fisheries through restrictive regulations for many years. Part of the problem is that there are many dedicated panfish anglers who strive to catch and keep as many large bluegills and panfish as legally possible. The larger bluegill is very vulnerable when they are spawning and a spawning closure could be considered to help maintain larger bluegill. Unfortunately, if conditions delay spawning, they can continue to spawn during the summer. This fact makes it very unpredictable to protect bedding bluegills with spawning fishing season closure.
I found, as a management biologist for many years, that the skilled panfish-harvest community is very well informed about the lakes that consistently produce good numbers of larger bluegills. That is the case for many of the bluegill-targeting anglers, even when they are from out of state or a long distance from the waters. With a liberal bag limit of 25 fish and a possession limit of 3 days (75 bluegill), it is easy to see how a quality water that gets targeted by talented bluegill harvesters could get cropped off.
It is not easy to come up with restrictive regulations that will get angler support when most panfish anglers have a maximum harvest mentality.
Remember, to preserve bluegill quality, you need to practice selective harvest. The large male bluegill is often the key to maintaining a lake’s quality bluegill size structure.
The author, Bill Ziegler, is a retired MDNR Fisheries Management Biologist.
