MUSKEGON, Mich. (AP) — The amount of prey fish that provide food for the larger sport fish native to Lake Michigan fell last year to a record-low level, while populations rose among invasive species such as zebra mussels and the goby, according to a government survey.

The overall picture casts a cloud of uncertainty over the future of the lake’s sport fishery, said Jim Dexter, Lake Michigan basin coordinator for the Michigan Department of Natural Resources.

“The $64,000 question is, will the forage community (prey fish) hold up and continue to provide reasonable fishing in Lake Michigan and allow us to meet our objectives for maintaining native fish species? There’s a lot of angst out there,” Dexter told The Muskegon Chronicle for a story published Sunday.

Scientists from the U.S. Geological Survey’s Great Lakes Science Center found 60 kilotons of prey fish in the lake during an annual survey conducted last fall. That was the lowest volume recorded since 1973, when the government started tracking the abundance of alewife, bloater, rainbow smelt, sculpin and stickleback in the lake.

Such prey fish support salmon, lake trout, steelhead and other species of large fish coveted by anglers.

The density of invasive species such as zebra and quagga mussels in Lake Michigan tripled last year, while the number of goby increased 16-fold between 2005 and 2006, according to government data. Similar downward trends among certain prey fish were recorded in all five Great Lakes, researchers said.

David Jude, a research scientist at the University of Michigan, said he believes prey fish are suffering because zebra and quagga mussels are consuming huge amounts of nutrients that otherwise would be eaten by tiny organisms that fish need for sustenance.

Jude and other scientists familiar with the data said Lake Michigan’s prey fish populations appear headed in the same direction as those in Lake Huron. Alewife began to vanish from Lake Huron in 2002 and the chinook salmon fishery collapsed the following year, after two years of near-record catches.

Under the worst-case scenario, Lake Michigan’s alewife population would crash and the salmon fishery would follow suit.

There was some good news in the annual prey fish survey: The volume of slimy sculpin and ninespine stickleback in the lake increased in 2006 and the resurgent perch population remained strong.

The chinook fishing on the lake has been phenomenal for the past three years, despite a steady decline in the volume of adult alewife in the lake since 2002.

The four states around Lake Michigan reduced salmon stocking by 25 percent last year in a bid to bolster the shrinking alewife population.

Posted 4/24/2007