Beam trawl used to capture young-of-year lake trout at East Reef, Lake Michigan. Trawl is being deployed off the University of Wisconsin research vessel "Neeskay". Photo by C. R. Bronte.

Young-of-year lake trout captured at East Reef. Photo by John Jannsen.

Lake trout raised in Service hatcheries have been stocked at the Mid-Lake Reef Complex in south-central Lake Michigan for decades in an attempt to reestablish a self-sustaining population.  This large (1,100 sq miles) offshore area (25-40 miles from shore) was historically one of the most important locations for lake trout reproduction prior to the population collapse during the substantial and 1950s from overfishing and sea lamprey predation. 

Since 2006, Green Bay Fishery Biologist Chuck Bronte has been working with John Jannsen from the University of Wisconsin-Milwaukee, to determine the extent of natural reproduction at East and Sheboygan Reefs within the Mid-Lake Reef Complex.  Using a both a Remote Operated Vehicle equipment with an electroshocker and suction capture device and an 8 ft wide beam trawl, the researchers have been looking for young-of-year (those hatched in the spring) lake trout at these locations.  Catches in 2006 and 2007 were disappointing and yielded less than 20 fish per year in total from all efforts.  On June 16, 2008 all that changed when 50 baby lake trout were captured in 6 of 7 beam trawl tows at the East Reef.  The fish were between 0.7 and 1.1 inches in length and some still had their yolk sacs indicating that they recently hatched.  Estimated densities at East Reef appear to be higher than at a similar location in Lake Superior were natural reproduction has been measured previously. The specimens will be used to determine hatching dates by examining the daily rings on the ear bones and the strains of lake trout that likely contributed to these offspring by genetic analysis.