December 2, 1998
Web posted at: 3:50 PM EST

By Environmental News Network staff

In the Great Lakes, many salmon and trout are sustained by the stocking of young hatchery-reared fish.

(ENN) -- To a fisherman, there couldn't be a lake with too many fish. But a Michigan researcher has asked what happens when a lake has too many salmon and trout? And the answer isn't good news if you're a fish.

"The food supply for salmon and trout can be driven down below levels that can sustain the fish populations, which could cause a large die-off of these predators. Chinook salmon, the most important sport fish species in three of the Great Lakes, appears to be the most vulnerable to a food supply shortage," Michigan Sea Grant's Jim Bence says.

In the Great Lakes, many salmon and trout are sustained by the stocking of young hatchery-reared fish. This means that an annual decision by the fishery managers is crucial: How many should be stocked? Sea Grant-funded researchers have collected extensive data on Great Lakes salmon and steelhead trout to assist in this process.

In today's world of crashing fisheries, it's important to have as many answers as you can. Sea Grant researchers are developing a simulation computer model of Lake Michigan fish, including salmon and trout and their prey, to predict likely responses of the fish to different management scenarios.

The researchers are asking questions like: Should stocking change from year to year in response to perceived conditions (e.g., abundance of food fish), or is a steady stocking rate better in the long-term? The researchers hope that by determining the answers, management agencies will be able to achieve objectives for the fish community, increase benefits to the salmon sport fishery and avoid fishery collapses caused by overstocking.

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