Walleye in Lake Winnipeg show no genetic differences
Ann Arbor, MI — While evidence has shown walleye in some lakes return to the same location to spawn each year, this does not appear to be the case in Lake Winnipeg.
Walleye are the main contributor to Manitoba's multi-million dollar commercial fishery, with Lake Winnipeg providing the largest and most profitable catch. In some systems, walleye show evidence of returning to the same spawning site each spring (i.e., philopatry), which can lead to the existence of multiple genetically-discrete spawning groups (i.e., stocks) within a lake.
"It’s important to know the number of stocks present in a system when managing a lake with a large fishery" says Stephanie Backhouse-James, of research she did while completing her Masters degree at the University of Manitoba. "If multiple stocks are present, sampling can provide valuable information about the number of fish being produced in different areas of a system. However, walleye do not always return to the same spot to spawn, and multiple stocks are not always present, which appears to be the case in Lake Winnipeg".
This study used genetic tools (microsatellites and mitochondrial RFLP’s) to assess the genetic differences of walleye taken from multiple spawning locations in Lake Winnipeg, as well as walleye taken from other locations outside of Lake Winnipeg. Slight genetic differences were found in walleye captured at one location in northern Lake Winnipeg, with all other sampling locations showing no differences. Walleye from outside of Lake Winnipeg showed slight to moderate genetic differentiation compared to walleye from within Lake Winnipeg.
"The results are surprising, because physical differences have been found between walleye taken from different locations within Lake Winnipeg, including the appearance of dwarf walleye, and differences in colour, growth and maturity rates" says Backhouse-James. "The lack of differences could indicate a low degree of philopatry, an amount of straying sufficient to obscure genetic structure, or obscured structure as a result of historical and current stocking into Lake Winnipeg."
Original Publication Information
Results of this study, "Microsatellite and mitochondrial DNA markers show no evidence of population structure in walleye (Sander vitreus) in Lake Winnipeg," are reported by Stephanie Backhouse-James and Margaret Docker in the special issue on Lake Winnipeg, of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact Stephanie Backhouse-James, Manitoba Hydro, Winnipeg, MB; sbackhouse@hydro.mb.ca, (204) 360-3476.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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