SEX REVERSAL OF YELLOW PERCH Perca flavescens EXPOSED TO 17α-METHYLTESTOSTERONE OR ESTRADIOL BY IMMERSION OR ORALLY AND GROWTH STUDY FOLLOWING EXPOSURE  

Kristen Towne*, Konrad Dabrowski
 
 School of Environment and Natural Resources
 The Ohio State University
 Columbus, Ohio 43212
 towne.19@osu.edu

Yellow perch have become a popular food fish in the last several decades due to their taste, firm flesh and low muscle fat content. The females of this species grow faster and to a larger final size than the males, resulting in their superior value in aquaculture. One option to obtain an all-female generation of this species is through sex reversal. By producing "neomales" (genetic females, but phenotypic males), we can obtain solely X-sperm, thus producing an entire generation of female fish. Masculinization is carried out with the use of 17α-methyltestosterone (MT), while the production of phenotypic females from genetic males is done using estradiol (E2). Previous authors have attempted to produce neomale yellow perch, but with only marginal success, likely due to the late timing of hormone exposure relative to sexual differentiation. The present study was conducted to determine efficiency of masculinization and feminization in fish less than 13 mm total length, and if growth differences are present following exposure to those hormones.

The fish (12.14 ± 0.44 mm) were exposed to the hormone via: MT-Diet (fed MT-enriched live Artemia nauplii for 21 days), MT-Immersion (subjected to a 4 h MT bath on 4 occasions), or E2-Immersion (subjected to a 4 h E2 bath on 4 occasions). Control fish were not exposed. Success of the sex reversal will be determined this December after several months of growth. At the conclusion of the hormone exposure phase, the fish were transferred to the recirculation system, while remaining separated by replicate. A 4-week feeding trial was conducted in a recirculation system containing 12 aquaria, 30 L each. Once the fish had acclimated to the new system and had accepted a formulated diet (21 days), all fish in each tank were weighed and the number was counted. Fish were fed Otohime S1 and S2 (when they reached an appropriate size) at a rate between 3% and 7.5% body weight (BW) per day. After 4 weeks, the fish were weighed again and tank density was recounted.

The specific growth rate of fish exposed to either hormone by either means of delivery did not significantly differ from one another or the control (P=0.6091; Table 1). These results indicate that exposure to sex reversal hormones does not have an impact on the growth of yellow perch following the exposure.