GnRHa-induced ovulation of brown trout (Salmo trutta) and its effects on egg quality

TitleGnRHa-induced ovulation of brown trout (Salmo trutta) and its effects on egg quality
Publication TypeJournal Article
Year of Publication1992
AuthorsMylonas, CC, Hinshaw JM, Sullivan CV
Pages379 - 392

The effectiveness of a GnRH analogue (GnRHa) for inducing ovulation in brown trout was examined, and the effects of the maternal hormone-treatment on egg quality and larval development were evaluated. Two injections of 10 μg/kg body weight of GnRHa given 3 days apart effectively induced ovulation. Within 6 days from the second injection, 80% of the injected fish had ovulated compared to only 10% of the control fish. Mean time to ovulation was reduced significantly (P < 0.01) from 15.4 days in control fish to 5.9 days in fish injected with 10 μg/kg GnRHa. Ovulated eggs from fish injected with this dose of GnRHa had lower fertility, survival to eyeing (eye-pigment formation stage) and hatching rates compared to eggs from fish injected with lower GnRHa doses or from control fish. Survival from hatch to complete yolk-sac absorption was not affected by GnRHa treatment. Reduction of egg quality was correlated with decreased time to ovulation in both control and GnRHa-treated fish, suggesting that poor egg quality did not result directly from the effects of the hormone on the maturing oocytes. Of the egg quality parameters examined, fertility was the one affected most by early ovulation. It is hypothesized that GnRHa-induced maturation caused a reduction in egg quality by disrupting the timing of final oocyte maturation and ovulation. © 1992.


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