Trawl fishing study tracks bycatch in Wisconsin

Commercial fishing sometimes unintentionally kills non-target fish, but early results from an experimental lake whitefish trawl fishery suggest minimal impact on gamefish.

This is a loop tag recovered from a lake trout caught by Reel Action Fishing Charters near Holland, Mich. Photo: Capt. Tom Manthei

This is a loop tag recovered from a lake trout caught by Reel Action Fishing Charters near Holland, Mich. Photo: Capt. Tom Manthei

The lake whitefish is a prized catch when it comes to commercial fishing in Lake Michigan. Through the years, a variety of different net designs have been used to catch lake whitefish.  As in any commercial fishery, bycatch of other species is a concern. 

In most areas of Lake Michigan, state-licensed commercial fishing operations are limited to the use of trap nets. Trap nets have the advantage of trapping fish in a large holding area called the pot. Pots are large enough that several thousand fish can swim freely in the net and survive for several days before the net is retrieved. This means that non-target fish like trout and salmon can generally be released alive and unharmed.

Another type of net is now being tested by a fishing operation on the Wisconsin side of Lake Michigan. A trawl net is very different than a trap net. Instead of being anchored to the bottom and waiting for fish to swim in, the trawl is actively dragged through the water. The net and its catch are brought on board with a heavy-duty winch after being dragged for 30 to 45 minutes behind the vessel. Many fish are alive and in good condition when brought on board, but not all. The end or bag of the trawl has large mesh (4.5 inches across), which allows smaller fish to escape before being raised to the surface.

The Susie Q. Fish Company, which operates out of Two Rivers, WI, has a history of trawling, first for alewives, then smelt, and now to target lake whitefish. This is an experimental fishery started in 2015, which is permitted to operate by the state of Wisconsin with the purpose of studying the rate of bycatch in different depths and seasons. Cooperation between the commercial fisher, Sea Grant, and the DNR make this research possible.

That is where Sea Grant comes in. Dr. Titus Seilheimer, fisheries specialist with Wisconsin Sea Grant, has been spending a lot of time out on the water counting and measuring catches on the Susie Q. Fish Company’s trawler, the Peter Paul. In all, he collected data from 491 net drags during a 65-day study period last year.

Good news for anglers

Seilheimer found that trawling was surprisingly selective for legal-sized whitefish. In fact, less than 3 percent of trawl-caught fish were bycatch. Most of these were lake trout or sublegal whitefish. Favored gamefish were almost completely avoided.  No steelhead or coho salmon were caught in trawl tows. One brown trout and three Chinook salmon were caught in 65 days of trawling – less than a daily limit for a single sport angler in Michigan waters.

Look for lake trout tags

Lake trout made up a larger fraction of bycatch, and the stress of being caught from deep water, handled, and released can be fatal. Seilheimer tagged trawl-caught lake trout to find out if released fish are surviving. “Lake trout are a hearty fish, and recovered quickly when placed in a recovery tank on the trawler,” Seilheimer reported. Of course, the tags must be returned to make the survival calculations work.

Anglers should be on the lookout for brightly-colored orange loop tags on lake trout. The tags are anchored behind the dorsal fin. Each tag has a phone number and unique ID number printed on it. If you catch a lake trout with one of these tags, be sure to call the number and report where you caught the fish.

Seilheimer has already heard back on the whereabouts of some of the trawl survivors. One lake trout travelled over 300 miles into Canadian waters of Lake Huron. Another was caught over 100 miles away near Holland, Mich. (See photo.)

Although lake trout are no longer being tagged as part of the study, collection of other data continues. The future of lake whitefish trawling operations in Lake Michigan is uncertain at this time, but this research will help to inform management decisions on permitting of trawl operations for Great Lakes whitefish.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

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