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Wisconsin DNR fisheries biologists have just completed phase one of an Alewife Dietary Study to determine whether these fish may be eating more than their share of yellow perch larvae. Night time gill-netting for alewives was performed over a two week period on traditional perch spawning grounds in Lake Michigan just off of St. Francis , WI.
Fishery biologist hope to get a good handle on exactly what , at this time of the year in Lake Michigan, makes up the alewife diet picture. Jim Thompson, fisheries biologist, said " we hope this diet study will give us a better understanding of the alewife diet in order to determine if there is an anecdotal absence of a peticular phytoplankton or organism which could be key to what has been happening to larval perch." A Laboratory research study indicates alewives can capture 90 percent of larvae too young to swim on their own by opening their mouths and just cruising through the water. Alewives first appeared in Lake Michigan in 1949 when they were introduced through ballast water discharge. Alewife are the primary food source for Lake Michigan's 80billion dollar recreational trout and salmon fishery .Until 1991, when their population fell, alewives were harvested commercially as an ingredient in pet food.
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Biologist try to unravel Lake Michigan perch decline mystery In March of 1997, the National Biological Service reported alewives now account for 43% of Lake Michigan's forage base bio-mass,
So far, biologists have determined that few alewives are coming into shallow waters to spawn, which means they're not gorging on the helpless larvae. The researchers have harvested 340 alewife stomachs. "Our work has just begun", said Thompson, " We have gathered a tremendous amount of data , now the data analysis portion begins and is a very time consuming and meticulous process. Each sample must be looked at microscopically and could take months." "Commercial fishing businesses have blamed the perch decline on alewives," Thompson said. "The public, too, has come to link loss of perch with the growing number of alewives because more of these fish have been dying and washing up on beaches in the last two years." "But there were several years in the 1980s when high perch survival coincided with alewife abundance," Thompson said. "It's too convenient to put all the blame on alewives without studying weather, health and all the other factors." |
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U.S. Fish and Wildlife Service is proposing to allow aquaculturists in 33 states to take cormorants that are preying
on their fish stocks.
The proposed rule, published in the June 23, 1997, Federal Register, would
save as much as $20 million in fish each year in the $714 million
aquaculture industry, the Service estimates. Much of the impact would be
felt in the Mississippi Delta region where catfish farmers lose an
estimated 3 percent to 7 percent of their inventory each year to the birds.
The order would affect all states in the great lakes region.
For years, Great Lakes anglers and Conservation Clubs have been complaining to resource departments that the increased population of these birds have been adversly affecting fish stocks.
Although this order is intended to serve the aquaculture industry, Great Lakes anglers are hopeful this will stimulate dialog to address their concerns.
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 Cormorants are long-necked, large-bodied, diving birds. Their webbed feet and hooked beaks are adapted for chasing and capturing fish under water. The double-crested cormorant is the most widely distributed of the six North American species, occupying a variety of coastal and interior wetland habitats. As of 1992, it had been found breeding in 40 of the 50 United States, all 10 Canadian provinces, and in Mexico, Cuba, and the Bahamas. The proposal would have no impact on the health of the cormorant population, which is at an all-time high of 1 to 2 million birds and increasing at a rate of 8 percent a year. The Service is permitted to issue special depredation orders for specific species of migratory birds to address particular problems under the Migratory Bird Treaty Act, which generally prohibits take of migratory birds except for game birds during regulated hunting seasons. |
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