Abstract:

Sand whiting Sillago ciliata, were captured since netting ocean beaches. Mature females were given single intraperitoneal injections of 300 IU•kg^-1 human chorionic gonadotropin (hCG) or 0.5 ml•kg^-1 Ovaprim (a synthetic GnRH analog with domperidone). One female and a spermiating male were then placed in 70^-1 or 1,000^-1 tanks. Both hCG and Ovaprim induced ovulation but not spawning in 38% and 75% of females, respectively (n=8). Females injected with distilled water (n=4) failed to ovulate. Fish were stripped, and the eggs fertilized 32-48 h after injection; mean fertilization was 85.6±12.0% (n=6) in females injected with hCG or Ovaprim, respectively. Tank size had no apparent effect on the number of females that ovulated. A separate experiment was conducted to determine if naturally ovulating females could be successfully collected from the wild and stripped. The mean fertilization in naturally ovulating females was 71.0±17.1% (n=4), lower than for Ovaprim-injected mature fish collected at the same time (89.5±12.0%, n=2), but higher than in hGC-injected fish (32.7±5.5%, n=3). The fertility of eggs from females injected with hCG was higher in the first experiment. Reasons for the different response to hCG between experiments were unclear, but the results suggest that Ovaprim is a more reliable hormone that hCG for inducing ovulation in sand whiting.

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Date 1996/12/01

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