Which Witch is Which? A Study of the Stock Structure of Witch Flounder (Glyptocephalus cynoglossus) in the Newfoundland Region

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Abstract
Genetic variability at two protein loci (phosphoglucomutase and superoxide dismutase) was assessed both within and among three major management areas for witch flounder (Glyptocephalus cynoglossus) in the Newfoundland region. The genetic analysis revealed population subdivision within each of the major management areas, giving a total of six subpopulations or stocks. These genetically defined stocks also differed with respect to population structure, time of spawning, individual growth rate, and temperature and depth of capture. These results suggest that witch flounder in the Newfoundland region exist in relatively small, independent subpopulations with little inter-stock migration. This population structure is at odds with current practices of managing witch flounder as large homogeneous stock units.Key words: witch flounder, stock discrimination, biochemical genetics, phosphoglucomutase, superoxide dismutase, electrophoresis