Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 26, 2003
Publication Date: January 28, 2004
Citation: Davis Jr, K.B., Ludwig, G.M. 2004. Hormonal effects on gender differentiation and growth in sunshiine bass morone chrysops x morone saxatilis. Aquaculture. 231:587-596. Interpretive Summary: Aquaculture production of striped bass and hybrid striped bass is the fifth largest form of fish production in the United States, trailing catfish, trout, salmon and tilapia. The most widely used hybrid is the sunshine bass, produced by crossing a female white bass with a male striped bass. Female sunshine bass are thought to grow to market size faster than male fish, therefore, it would be desirable to raise only female fish. All female sunshine bass populations can be produced by feeding estrogen in the feed for 40 days from day 60 or 103 day old fish. Feeding testosterone during the same period did not produce all male fish. Some intersex fish, having elements of ovarian and testicular tissue, were produced when the fish were treated with testosterone when they were 60 days old. Testosterone in the diet did not increase the growth of fingerling sunshine bass and estrogen decrease the growth rate. The growth advantage for females is not apparent until the second year.
Technical Abstract: Aquaculture production of striped bass and hybrid striped bass is the fifth largest form of fish production in the United States, trailing catfish, trout, salmon and tilapia. The most widely used hybrid is the sunshine bass, produced by crossing a female white bass with a male striped bass. During production, the fish are graded several times to avoid loss due to cannibalism. Such grading of fish may that exhibit sexually dimorphic growth could result in changing the sex ratio of populations raised for food production. A preferred gender exists for most aquaculture species. We have found that during their first year, male sunshine bass appear to grow faster than females; however, females grow faster during the second year and are usually heavier when the fish are harvested. Feeding methyltestosterone did not increase the growth of fingerling fish; however, feeding estradiol decreased growth, apparently by decreasing feed consumption. Immersion treatment of four-day-old fry for up to 8 hours with methyltestosterone or estradiol did not change the sex ratio. Treatment of 60-or 103-day -old-fish for 40 days with estradiol in the feed resulted in all female fish. Methyltestosterone treatment during the earlier period resulted in intersex fish and treatment of 103-day-old-fish did not change the sex ratio. Direct feminization with estradiol can be achieved during a period of development in which direct masculinization with methyltestosterone is not effective.