July 30, 2020
By Scott Mackenthun
At an annual gathering of fisheries researchers, scientists, managers and students, Dennis Pratt gave one of his final talks as a biologist for the Wisconsin Department of Natural Resources prior to his retirement. Best known for his work with trout and salmon in Lake Superior and its tributaries, Pratt switched gears and took the opportunity to talk about the astonishing lack of large bluegills in the state of Wisconsin.
His message was simple: Large bluegills needed some help and attention. The small crowd of fisheries professionals in the audience nodded their heads in agreement as he spoke.
To illustrate his point, Pratt reviewed bluegill data from Wisconsin’s survey database and discovered that you'd have a better chance of being dealt a royal flush in a hand of five-card stud— 649,739-to-1 odds—than catching a bluegill over 10 inches on a random Wisconsin lake. That simple statistic framed a vexing reality: Big bluegills have long been rare creatures, but in modern times they are all but gone.
The disappearance of large bluegills isn’t unique to Wisconsin. Old panfish anglers recall stories of the big-bluegill glory days of their past, and they fit with observations gleaned from regional datasets. Studies in Minnesota, Wisconsin and Nebraska have documented large-fish declines in historic catch, either with statewide survey records or winning entries in long-running fishing contests. Other Midwestern states have similar observations or likely would if their datasets were more robust and went back far enough.
Reasons for the Decline
By their nature, big bluegills are susceptible to overharvest. Their gregarious schooling tendencies cluster the fish in prime habitats where anglers can easily find and catch them. Their curiosity and need to forage for large numbers of insects and big-bodied zooplankton make them willing biters. Their spawning strategies make them especially vulnerable. Bluegills, like other sunfish, begin spawning over nests in shallow water in late spring. They often occupy similar locations from year to year. With no closed season on bluegills on most Midwestern waters, male bluegills are easily caught and removed.
Male bluegills exhibit alternative life-history strategies. Large "parental" males delay sexual maturity, which allows them to devote their energy resources to growth rather than reproduction. In contrast, some smaller males can operate as cuckolds. They sneak in to spawn unfertilized eggs in a "sneaker" role. A small male can also pass as a female by way of its smaller body size and lighter coloration. These fish will sometimes squeeze between a spawning female and parental male in a "satellite" male role, fertilizing eggs in the process.
Both sneaker and satellite males can be sexually mature as young as two or three years of age, whereas parental males will delay sexual maturity until age six or seven. Sneaker and satellite males provide no parental care. Parental males excavate spawning nests and work to guard the nest and eggs by running off predators and other competing males. When anglers harvest parental males, they remove fish that are critical to ensuring that large-bodied, fast-growing genes are passed to the next generation. Removing the largest bluegills in a lake, as many anglers hungry for a meal are wont to do, takes out a disproportionate number of critically important parental males, not just during the spawn, but throughout the year.
For years, bluegill anglers interpreted selective harvest as keeping the largest fish and releasing smaller fish to grow to larger sizes. In doing so, they took out the fastest-growing and largest-bodied fish. They also removed the oldest fish. Midwestern bluegills can grow as old as 10 to 12 years, which might be an underestimation. Put simply, it takes time to grow large bluegills, and when harvest is high, there isn’t enough time, or enough other large fish coming up, to replace the big fish that are removed.
Because bluegills have been available to Midwestern anglers—and so easily caught—for so long, they have been a staple of fish fries for generations. As such, attempts to regulate harvest have been historically unpopular. But attitudes might be changing. Recent human dimension surveys in Minnesota have documented angler dissatisfaction with the small size of bluegills. It appears that anglers are willing to give up some of their bag limit if they can catch larger fish. A quarter-century of research into bluegill dynamics across the Midwest by state biologists and academics has shown that only very drastic cuts to bag limits are enough to produce meaningful results that maintain or improve large bluegill sizes.
In 2018, North Dakota cut its bag and possession limit in half. South Dakota is collecting data on a set of big-bluegill waters to see how much harvest is occurring. It could consider regulations if harvest of large bluegills is identified as a problem. In Wisconsin and Minnesota, lakes with reduced bag limits are producing large bluegills, and there are proposals to add more waters to a growing list. Preliminary public support in Minnesota and Wisconsin has been favorable—quite a contrast to similar proposals just a decade earlier. In other states, enacting a limit on public waters will be a first step. Kansas, Illinois, Indiana and Ohio do not have any bag or size limits on bluegills.
Anglers who value large bluegills will need to do their part. To have big bluegills in the future, they will need to exercise restraint by releasing bluegills more than 8 inches in length and keeping only smaller fish. They also need to support more restrictive regulations proposed by management agencies. Even with biological justification, social opposition can squash useful regulations.
As modern fishing technology increasingly gives anglers the upper hand, now more than ever, discretion and responsible use is critical through selective harvest that releases the largest fish in the population. Without regulated or voluntary release of large bluegills, Midwestern bull bluegills on many waters won’t be available for the next generation of anglers.