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William D. Swink

Sex determination mechanisms in fishes lie along a genetic-environmental continuum and thereby offer opportunities to understand how physiology and environment interact to determine sex. Mechanisms and ecological consequences of sex determination in fishes are primarily garnered from teleosts, with little investigation into basal fishes. We tagged and released larval sea lamprey (Petromyzon marinus) into unproductive lake and productive stream environments. Sex ratios produced from these environments were quantified by recapturing tagged individuals as adults. Sex ratios from unproductive and productive environments were initially similar. However, sex ratios soon diverged, with unproductive environments becoming...
Abstract.—Coded wire tags were injected into the dorsal musculature near the insertion of the dorsal fin (dorsal location) and subcutaneously along the ventral midline posterior to the anus (ventral location) of larval and small parasitic-phase sea lampreys Petromyzon marinus. In larvae, tag loss after 1 year was significantly higher (P < 0.01) from the ventral location (18%) than from the dorsal location (1%). Although only 14 tagged larvae metamorphosed during the study, the process did not seem to increase tag loss. Mortality of larvae tagged in either site did not differ from controls (P > 0.57). Parasitic-phase sea lampreys lost no tags from either site through 99 d after tagging. Mortality was high in all...
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