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Title: Identification of gender in yellow perch by external morphology: validation in four geographic strains and effects of estradiol

item Shepherd, Brian
item Rees, Christopher
item Sepulveda Villet, Osvaldo
item Palmquist, Debra
item BINKOWSKI, F - Water Institute

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2012
Publication Date: 5/13/2013
Citation: Shepherd, B.S., Rees, C.B., Sepulveda Villet, O.J., Palmquist, D.E., Binkowski, F.P. 2013. Identification of gender in yellow perch by external morphology: validation in four geographic strains and effects of estradiol. North American Journal of Aquaculture. 75: 361-372.

Interpretive Summary: A non-lethal and rapid method for reliable identification of gender in yellow perch has been developed. On average, yellow perch females grow faster than males. Such size discrepancies in mixed culture situations pose difficulties with aquaculture production. ARS researchers at Milwaukee, Wisconsin, have developed criteria that enable gender identification in yellow perch based upon the coloring and shape of the external reproductive openings with an accuracy exceeding 97%. This non-lethal method provides a useful and practical tool that will enable producers and researchers to cost-effectively sort sexes for many uses, including: 1) development and management of broodstocks prior to, and during, breeding; 2) conducting multi-tank replicate experiments aimed at studying gender-specific differences in yellow perch; and 3) identification of the fastest growing individuals of each sex in yellow perch broodstock genetic-selection programs dedicated to developing improved growth performance in this species. In addition, since this method allows for the unharmed release of each animal, it can be used in the field during wild yellow perch population surveys involved with characterizing reproductive health status.

Technical Abstract: External morphological criteria that enable the rapid determination of gender have been developed for yellow perch (Perca flavescens). Criteria are based upon 1) shape of the urogenital papilla (UGP), 2) relative size of the UGP to the anal (AN) opening, and 3) coloration of the UGP. In females, the UGP appeared 1) rounded at the anterior margin, 2) pointed at the posterior margin with a V or U shape (crescent shaped in mature animals), 3) generally lacked reddish coloration, and 4) the UGP was narrower relative to the AN. In males, the UGP appeared 1) circular or oval around the entire margin, 2) typically displayed reddish coloration, and 3) was generally more wide relative to the AN. To verify accuracy of these criteria, gender was verified internally in perch of various sizes, sex and maturity from four domesticated geographic strains (n = 1,389). For all perch tested, accuracy was 97.3% for both sexes, 98.8% for females and 95.9% for males. To experimentally verify accuracy of these criteria, juvenile perch (n = 913) were treated with dietary estradiol (E2, 15 mg/kg diet) or a control diet. Accuracy was 97.7% for control females and 95.1% for control males, which diminished to 63.9% for the E2-treated females and 57.6% for E2-treated males. We have developed a gender identification algorithm that will enable sorting of sexes for many uses, including: 1) collection of broodstock by new aquaculture producers, 2) management of broodstocks for existing producers, 3) improved selection criteria for genetic selection programs, 4) studies on gender-specific differences in perch physiology, and 5) the unharmed release of animals in the field and aquaculture setting. Uncoupling of external UGP morphology from actual gender in E2-treated perch can enable producers and biologists to detect exposure to estrogenic compounds in areas where endocrine disruption is suspected.