Over harvest of bluegills

[Lee Borgersen]

  Research reverses thoughts on overharvest of bluegills :fishing2:
                                                                                                             

By Anthony Candia Contributing Writer

Posted on January 4, 2016

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Lake Orion, Mich. —  For years, farm pond owners across the state have followed a simple belief when stocking and managing bluegill populations:

Bluegills are prone to overpopulation, and if you don’t catch and keep a lot of them, you’ll end up with a pond full of runts.

But the word out of the north is that the belief is wrong. Michigan pond owners may want to adjust their thinking.

Research conducted by Andrew Rypel, a research biologist with the Wisconsin DNR, suggests that overharvest of bluegills actually decreases the size of fish.

“Our managers have observed a long-term demise in panfish size,” Rypel said. “When I started at DNR, I did this analysis where we looked at all the size data we had for bluegills, yellow perch, and crappies. It turns out in all three cases, all have been declining for the last 70 years. That basically is a management problem we were dealing with. You can see it at a regional scale, also at individual lakes.”

In Michigan, there is a 25-fish daily possession limit in combination with other sunfish. Wisconsin, like every other state, had quite liberal harvest limits. Until 1998, anglers were allowed to harvest an aggregate of 50 panfish per day. It was dropped to 25 in 1998. 

“That’s still pretty high when you consider the life history of some of these species,” Rypel said. “We’re starting to get better age data on bluegills – some live to be in the mid-teens. That’s a high replacement rate. It takes a long time to replace that biomass once it’s been removed.”

The regulations are relatively liberal, he said.

“I thought one possibility might be that we were fishing them too hard,” he added. “As we looked at the data, we found that evidence of bluegills becoming stunted because they were overpopulated was not as common as previously thought.”

Fishing pressure, particularly on spawning beds where bluegills are most vulnerable, can be intense. And that pressure may be decreasing the size of fish.

In response to the trend, the Wisconsin DNR reduced the bag limit to 10 fish on 10 lakes as a test. Researchers, including Rypel, analyzed fish size before and after the regulation.

They found that fish size increased on average a half-inch on maximum size and .8 inches on mean size.

That may not sound like much, but consider that a typical bluegill is 6 or 7 inches, and a really large one is 10 inches.

Rypel published the findings of his study in the North American Journal of Fisheries Management.

One aspect of the research that could help pond owners and lake managers in other states is that Rypel and his crew cast a wide net, so to speak.

“We identified these lakes based on size and growth,” Rypel said. “If a lake had poor size structure, but good growth rates, that suggested that angling was a problem. They had the scope for growth, but they weren’t getting to that size. These would not be lakes people would refer to as stunted lakes. These were lakes that could be much better that weren’t performing.”

The next phase of the project is to implement new management strategies on 100 lakes. One-third will have a reduced limit of 10, one-third will have a reduced limit of five, and one-third will have a reduced bag limit only during the spawning season.

The management regimes will run for 10 years. “We’re going to find out what different regulations can do for panfish size,” Rypel said.

There is still a lot biologists don’t know about bluegills. New research likely will call for more changes in fishing regulations, but Rypel acknowledged that science is only one part of fisheries regulation.

“Regulations are a blunt instrument,” he said. “We want regulations that are easy to understand and easy to enforce.”

And while the bluegill may seem an unlikely symbol for global fisheries management, what Rypel said applies to large commercial fisheries as surely as it does the local farm pond. Regulations are only partly about science, and they can never fully account for the complexity of a fishery.

The key for resource managers is to use sound science to create regulations that work best – for fish and for people.

“Bluegills have the opportunity to get bigger with a relatively minor shift in fishing regulations,” Rypel said. “Our research is providing the evidence that it benefits anglers, too. The findings seem counter-intuitive to many anglers, who have long believed that smaller bluegills was a sign of overpopulation. But perhaps our long-term studies can convince them that lower bag limits can mean better fishing, and bigger panfish fillets for the fish fry.”