ONEKAMA, Mich. (AP) -- Salmon fishing on Lake Michigan has been good in recent years, but increased numbers of smaller fish being caught are making anglers nervous.

It's the same phenomenon that preceded a collapse of the salmon fishery in Lake Huron around 2003.

Should that happen on Lake Michigan, it would be a big blow to the state's outdoor economy.

Charter boat captain Denny Blue says six charter boats dock at Portage Lake in Onekama. The lake links to Lake Michigan north of Manistee in the northern Lower Peninsula.

He says at least 200 boats based on Portage Lake are rigged to catch sport fish, mainly chinook salmon.

The decline in chinook population in Lake Huron led to a drop of about 75 percent in fishing, the Michigan Department of Natural Resources says.

The salmon population collapsed because of food chain changes, most likely caused by the spread of invasive species like the zebra and quagga mussels.

Biologists have observed the near-disappearance of diporeia, a shrimp-like crustacean that

(Copyright 2007 by The Associated Press. All Rights Reserved.)