Inside Angles: Fillet Weights and Fishery Management

In-Fisherman proposed the concept of selective harvest in the late 1980s. It encourages keeping more numerous smaller fish for the table while releasing less abundant larger fish to sustain good fishing. As we’ve so often said, fish are nutritious and delicious, and when they’re harvested wisely (selectively) they’re a renewable resource. As In-Fishermen, we can continue to enjoy fine meals as we also support fine-quality fisheries that host good fishing for larger fish.

Many anglers, though, are most interested in just harvesting fish. It can be hard to convince them that management approaches like lowering bag limits to increase fish size are in their interest. They often believe the inevitable outcome will be a reduced amount of food to take home (in terms of fillet yield).

One of the most ingenious methods for convincing anglers to support lower bag limits came from a study by the Wisconsin Department of Natural Resources, which was previously reported in In-Fisherman. The researchers determined the relationships between fillet weight and yield and fish size for bluegills, black crappies, and yellow perch caught by anglers from Wisconsin waters. Along with creel survey and fishery data, they then examined how fillet yield might be a useful measure for exploring regulation changes.

For bluegills, for example, they showed how increases in fish size under a daily limit reduction from 25 to 10 fish could affect the total weight of fillets available to anglers. Despite the reduced daily limit, they demonstrated that anglers could be able to take home the same or even more fillet weight. Under a daily bag limit of 25 fish, Wisconsin creel data showed the average size of a harvested bluegill to be 6.8 inches. If an angler kept 10 fish, they would take home a total of 10.8 ounces of fillets. By comparison, under a reduced daily bag limit of 10 bluegills for seven evaluation lakes, the average size of bluegills harvested was 7.6 inches. In that case an angler harvesting 10 bluegills would take home about 15.5 ounces of fillets.

Although similar attempts to justify bag limit reductions apparently haven’t been used with other species, they could be. In another test, the late Dr. Dave Willis and Brian Van Zee, working at South Dakota State University, determined walleye fillet weights (ribs out) for fish from lakes in the eastern part of the state. A 14-inch walleye that weighs close to 1 pound produces about 0.3 pounds of fillet. The fillet weights climb quickly as fish length increases. A 22-inch walleye produces about 1.5 pounds of fillet.

They suggested that anglers that like to eat walleyes but aren’t supportive of length limits should consider that two harvested 13-inch walleyes produce four fillets weighing about 0.44 pounds. One 16-inch walleye produces more fillet weight than two 13-inch fish (0.47 pounds). One 19-incher produces as much fillet weight as four 13-inch fish (0.87 pounds).

Of course there’s more at work in setting limits. According to In-Fisherman Managing Editor and fishery scientist Dr. Rob Neumann, length limits for panfish have shown most promise where panfish have fast growth, low natural mortality, and consistent recruitment. Under these conditions, when creel limits are set low enough to reduce harvest to meaningful levels and still be socially acceptable, a reduced bag can often improve size structure, so long as growth rate doesn’t slow.

Neumann notes that data such as those from the Wisconsin study can also be used to convince anglers to release larger fish as a matter of selective harvest. It’s tempting to harvest a 10-inch bluegill with thoughts of its fillets browning in butter, but it only takes a few extra 7-inchers and a few extra minutes with the fillet knife to make up for the fillet weight of that 10-incher—a bit of extra effort as a matter of conscience and conservation.

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