Delayed ovarian development and reduced serum steroid levels in female largemouth bass, Micropterus salmoides Lacepede, raised on pelleted feed
1999
Rosenblum, P.M. | Horne, H.L. | Swim, J.D.
Female largemouth bass, Micropterus salmoides Lacepede, were raised on pelleted feed or a forage diet consisting of goldfish. Carassius auratus (L.). At the start of the present study, forage-fed bass were significantly smaller than pellet-fed bass. Forage-fed bass exhibited a significant increase in body weight, but not length, during the first month of the study; no further increases were seen in subsequent months. Pellet-fed bass did not grow significantly during the course of the study. In forage-fed bass, the gonadosomatic index (GSI) reached maximum levels in March; pellet-fed bass exhibited delayed ovarian recrudescence, reaching peak GSI approximately 4 weeks later than the forage-fed bass. There was no significant difference in the maximum GSI obtained in the two groups of fish. Serum levels of testosterone and oestradiol-17 beta reflected the pattern of GSI in both groups. Delayed ovarian recrudescence and suppressed serum steroid levels in pellet-fed bass might result from negative feedback effects of elevated levels of steroids found in the pelleted feed. These effects appear to be transient since pellet-fed bass resume ovarian development despite continuing to receive high steroid levels in their feed.
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