Missing in Huron: Bottom feeders

The Detroit Free Press has an article on further research done on fish populations within Lake Huron:

Lake Superior is big, clear and beautiful, yet in terms of fish production it's a near desert compared to the other Great Lakes. Now fisheries scientists say changes they started seeing in Lake Huron a few years ago might mean that the second-biggest of the Great Lakes is on its way to becoming an equally unproductive version of Superior.

Fisheries biologists talked about Lake Huron this week at the Great Lakes Fishery Commission meeting in Windsor. They have been amassing huge amounts of information and can tell us what's happening with fish in the lake. But about all they can do is stand back and wait to see what happens next because they don't know how to fix things.

The problem apparently starts with some of the smallest creatures in the food chain.

Mary Balcer of the University of Wisconsin-Superior studies these tiny creatures. She found that fish can get much more energy by eating a tiny shrimp called diaporeia than from many other kinds of zooplankton. But diaporeia have almost disappeared from most of Lake Huron for reasons scientists have yet to figure out, although they suspect that diaporeia and other zooplankton can't compete with exotic zebra and quagga mussels that invaded the lakes.

Balcer also discovered that larval fish eat different sizes of zooplankton at different times in their lives, and the right size of zooplankton is no longer available at the right time for the little fish in most of the lake.

"We used to think the alewives disappeared because the salmon ate them all," said Jim Johnson, a DNR research biologist. "Now we learn from Mary Balcer's work that the alewives had the rug pulled out from under them when the zooplankton crashed,"