||Influence of Environmental Temperature on Sex-Ratios in the Tidewater Silverside, 'Menidia peninsulae' (Pisces: Atherinidae).
Middaugh, D. P. ;
Hemmer, M. J. ;
||Environmental Research Lab., Gulf Breeze, FL.
Marine fishes ;
Ocean temperature ;
Seasonal variations ;
Santa Rosa Island ;
Menidia peninsulae ;
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The sex-ratios of Menidia peninsulae from Santa Rosa Island, Florida were studied during a 13 month survey. Weekly samples revealed significant deviations from the expected sex-ratio of 1:1. During May-October, young-of-the-year (YOY) females comprised 70 to 94% of the individuals collected in the 32.5 to 62.4 mm SL size class. In contrast, collections of YOY Menidia during November-April yielded 34 to 60% females. These individuals are the presumptive progeny of reproductive activity and sexual differentiation in May-August at warm fluctuating water temperatures of 25.0 to 29.0C. The pattern in sex-ratios of older Menidia 62.5 - 102.4 mm SL paralleled that of YOY individuals. The annual (13 month) sex-ratio for collections of YOY and older Menidia was identical at 68% females.