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Green Bay FWCO Fish Biologist Assists with Isle Royale Lake Trout Research Project
Midwest Region, June 2, 2014
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Ashland FWCO Fish Biologist Mike Seider prepares a lake trout for a digital photograph.
Ashland FWCO Fish Biologist Mike Seider prepares a lake trout for a digital photograph. - Photo Credit: Kevin Pankow, USFWS
Green Bay FWCO Fish Biologist Kevin Pankow displays a lake trout captured gill netting near Isle Royale on Lake Superior.
Green Bay FWCO Fish Biologist Kevin Pankow displays a lake trout captured gill netting near Isle Royale on Lake Superior. - Photo Credit: Mike Seider, USFWS
The four principal morphotypes of lake trout found at Isle Royale, Michigan in Lake Superior. 
From: A. M. Muir, C. R. Bronte, M. S. Zimmerman, H. R. Quinlan, J. D. Glase & C. C. Krueger (2014).  Ecomorphological Diversity of Lake Trout at Isle Royale, Lake Superior, Transactions of the American Fisheries Society, 143:4,972-987.
The four principal morphotypes of lake trout found at Isle Royale, Michigan in Lake Superior. From: A. M. Muir, C. R. Bronte, M. S. Zimmerman, H. R. Quinlan, J. D. Glase & C. C. Krueger (2014). Ecomorphological Diversity of Lake Trout at Isle Royale, Lake Superior, Transactions of the American Fisheries Society, 143:4,972-987. - Photo Credit: Artist: Paul Vecsei

Fish Biologist Kevin Pankow, from the Green Bay Fish and Wildlife Conservation Office (GBFWCO), assisted the Michigan Department of Natural Resources (DNR), NOAA Northwest Fisheries Science Center, Ashland Fish and Wildlife Conservation Office, National Park Service and University of Wisconsin-Milwaukee the week of June 2 with a lake trout research project near Isle Royale National Park on Lake Superior.

 

The cooperative, 2-year research project, coauthored by Chuck Bronte from GBFWCO, was funded by a competitive grant from the Great Lakes Fishery Commission. The objectives of the project are to characterize the seasonal reproductive development, assess the genetic relatedness of individuals within a given morphotype collected seasonally to determine if they are derived from the same morphotype populations, and compare fecundity and skeletal muscle lipid levels among lean, siscowet, humper and redfin lake trout at Isle Royale. The two-year project began in 2013 and fish are sampled during spring, summer and fall.

Lake trout were captured by gill nets from the Michigan DNR Lake Char research vessel at multiple sites off the north shore of Isle Royale for three days. Alllake trout were assessed for length, weight, morphology, sea lamprey wounding and visceral fat index. Specimen collections included otoliths for ageing, a tissue sample for genetic analysis, and blood samples for plasma profiling . All fish were digitally photographed for morphometric measurements that are used for morphotype identification. In addition, gonads were removed, digitally photographed and weighed to calculate the gonadosomatic index (GSI). A cross-section of each pair of gonad was fixed for histological examination to determine the developmental stage of the gametes. Eggs were collected from mature females of each morphotype to determine fecundity.

Historical and recent accounts document that the various lake trout morphotypes reproduce at a variety of times during the year in Lake Superior, particularly at Isle Royale. Seasonal sampling will document the reproductive timing and spatial and temporal isolation of these forms. This research project will highlight more options for reestablishing lake trout populations in the lower Great Lakes that have lost their morphotypic and life history diversity.


Contact Info: Kevin Pankow, 920-866-1768, kevin_pankow@fws.gov



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