Commercial Trapnets in Central Lake Huron

Since 2001, two commercial operations have been operating in central Lake Huron and DNR has been working to avoid conflicts between user groups through communication. These two commercial fisheries usually fish a total of 17 trap nets between North Point of Thunder Bay and the Greenbush area south of Harrisville. These commercial fishers report their net locations with the DNR and we post them here (pdf of coordinates) to assist anglers and boaters in avoiding these nets. Fishers change their net locations often and this map is not updated in real time (some lag before updating) so anglers and boaters should not depend only on this map of net positions but should watch for buoys and markers.

Each state-licensed commercial trapnet is marked with three staff buoys and black or orange flags. In addition to staff buoys, nets are also marked with several red, yellow, white, or orange floats that are at least two gallons in size. The nets are set deep enough to allow for recreational and commercial boat traffic to move freely at the surface but fishermen should be mindful of the net location to avoid loss of fishing gear. There are also trap nets in Saginaw Bay and Native American fisher trapnets north of Thunder Bay permitted under the 1836 Consent Decree. These nets are not depicted on this map.

Photo of trapnets being emptied
The catch from trapnets is live when harvested and non- target species such as trout and salmon are released.

 

 

Why trap nets?

 

In the late 1960s, the Michigan Natural Resources Commission issued orders that banned large-mesh gill nets and required replacement of gill nets with impoundment gear (trap nets). The intent of the ban was to "encourage conversion to the more selective, highly efficient, less damaging, trap nets, which were considered to be compatible with the goals of lake trout restoration" (Rybicki and Schneeberger, Recent history and management of the State-licensed commercial fishery for lake whitefish in the Michigan Waters of Lake Michigan. Michigan DNR, Fisheries Research Report No.1960, 1990). New York, Ohio, and Indiana banned the use of gill nets in 1994. Ontario and most tribal fishing authorities continue to authorize gill nets in their commercial fisheries.

Gill nets, as their name implies, catch fish by entangling them in mesh, often in the gill area. Fish caught by the gills may suffocate or sustain irreversible damage to the gill arches including bleeding from the gills. At times, the fish are boxed with the net and removed from the mesh later; in these cases, mortality of the incidental (non-target) catch approaches 100%. Trap nets work like aquatic corrals, capturing fish in large holding pens called "pots". Trap nets cause much lower mortality of the incidental catch and are efficient in the capture of lake whitefish - the principal target of Lake Huron's commercial fishery. Because the fish are live when taken from trap nets, nontarget fish such as trout and salmon can be safely released. Whitefish from trap nets (because they are fresher) usually sell for more than gill-net-caught whitefish.

Michigan's State-licensed commercial fisheries on Lake Huron are required to release all trout, salmon, and walleyes. In Thunder Bay virtually all the harvest is composed of lake whitefish. A few carp, burbot, and channel catfish are occasionally also harvested. The whitefish catch can be purchased at a variety of stores and restaurants in the Alpena area.

 

For more on the history and ecological considerations of trap net and gill net commercial gear, see the following publications:

 

Johnson, J. E., M. P. Ebener, K. Gebhardt, and R. A. Bergstedt. 2004. Comparison of catch and lake trout bycatch in commercial trap nets and gill nets targeting lake whitefish in northern Lake Huron. Michigan Department of Natural Resources, Fisheries Research Report 2071, Ann Arbor.

Abstract. - We compared seasonal lake whitefish catch rates, lake trout bycatch, and gear-induced lake trout mortality between commercial trapnets and gillnets in north-central Lake Huron. Onboard monitors recorded catches from 260 gillnet and 96 trapnet lifts from October 1998 through December 1999. Catch rates for lake whitefish were highest in fall for both gear types, reflecting proximity of spawning sites to the study area. Lake whitefish catch rates were also relatively high in spring but low in both gear types in summer. Lake trout were the principal bycatch species in both gears. The lake trout bycatch was lowest in both gear types in fall, highest in gillnets in spring, and highest in trapnets in summer. The ratio of lake trout to legal whitefish (the target species) was highest in summer and lowest in fall in both gear types. The high lake trout ratio in summer was due principally to low catch rates of lake whitefish. All but 3 of 186 live lake trout removed from trapnet pots survived for at least two days of observation in laboratory tanks. Therefore, we estimated that post-release survival of trapnetted lake trout that had not been entangled in the mesh was 98.4%. In addition, we accounted for stress-induced mortality for lake trout that were live at capture but entangled in the mesh of either gear type. Resulting estimates of lake trout survival were higher in trapnets (87.8%) than in gillnets (39.6%). The number of lake trout killed per lift was highest during summer in trapnets and during spring in gillnets. In trapnets, 85% of dead lake trout were observed to be entangled in the mesh of the pot or tunnels. Survival rates of lake trout in gillnets were higher in our study than reported by others, probably because our nets were hand lifted in a small boat. Our trapnet-induced mortality estimates on lake trout were higher than those reported by others because we adjusted our estimates to account for post-release mortality caused by handling and injury. Studies such as ours should prove useful to managers developing harvest allocation options that are consistent with the need to protect nontarget populations. For example, applying our seasonal lake trout-whitefish catch ratios to a hypothetical small-boat gillnet fishery, the lake trout bycatch from harvest of 100,000 kg of whitefish would equal the estimated lake trout production available for harvest in the study area for year 2002. The two trapnet fisheries may have incidentally killed half this number of lake trout annually from 1995-1999. Bycatch estimates are also important inputs to catch-at-age decision models used in developing rehabilitation and harvest strategies for target and bycatch species.

 

 

Johnson, J. E., J. Jonas, and J. P. Peck. 2004. Management of commercial fisheries bycatch, with emphasis on lake trout fisheries of the upper Great Lakes. Michigan Department of Natural Resources, Fisheries Research Report 2070, Ann Arbor.

 

Abstract. - We investigated the collective published record on the significance and management of commercial fisheries bycatch at both global and Great Lakes regional scales to: 1) to identify elements of Great Lakes ecosystems that are especially vulnerable as fisheries bycatch; and 2) identify opportunities to minimize incidental catch of sensitive species in Great Lakes commercial fishing gear. The majority of the world's harvestable fisheries are fully- or over-exploited, and approximately a third of the global catch is composed of bycatch and discards. Bycatch can be characterized as the incidental catch of organisms that were not targeted in a given fishing effort. Significant levels of bycatch can contribute to overharvest. Therefore, it is essential to characterize bycatch when assessing impacts of fishing. Bycatch is not always measured; failure to measure bycatch can result in underestimation of fishing mortality and thus, overestimation of quotas available for harvest. Responsible fishing practices are being encouraged worldwide and most of these efforts have focused on reducing or eliminating the amount of bycatch associated with harvest of targeted species. The magnitude of the bycatch problem is typically proportional to fishing effort. In many cases, effort exceeds what is necessary to harvest sustainable yields of target species; thus, reduction of effort is often the single most effective tool in reducing bycatch. Other methods of managing bycatch include: development and use of more selective gear, prohibiting retention of bycatch, and use of incentives and penalties in quota management. Great Lakes fisheries have mirrored the global pattern of overfishing. Recovery programs for collapsed fish populations have necessitated restrictive harvest controls. Lake whitefish Coregonus clupeaformis populations have recovered, but lake trout Salvelinus namaycush are far from rehabilitated in lakes Ontario, Erie, Michigan, and Huron. Lake trout are the native keystone species of the upper Great Lakes, are the subject of immense rehabilitation efforts, and have vulnerability similar to lake whitefish to leading gear types used in Great Lakes commercial fisheries. Efforts to limit commercial fishing to more selective gear types have been only partially successful. Bycatch of lake trout in large-mesh gill nets set for lake whitefish has exceeded lake trout harvest quotas in some management units. The selectivity of gill nets is difficult to manipulate, especially when target and nontarget fish are of similar size and overlap in spatial distribution, as is the case with lake trout and lake whitefish. Trap nets are effective in catching lake whitefish and are less lethal to the catch than gill nets. Commercial bycatch, combined with targeted fishing for lake trout (recreational and commercial) and depredation by sea lampreys Petromyzon marinus, has contributed to the delayed rehabilitation of self-sustaining lake trout fisheries. Thus, we conclude that the widespread use of nonselective gear types such as gill nets in Great Lakes commercial fisheries is inappropriate in an era of shared resources and ecosystem-level rehabilitation efforts.

 

Photo: Trapnet being lifted in Thunder Bay.
Trapnet being lifted in Thunder Bay.