Induction and
synchronisation of ovulation in rainbow trout, Oncorhynchus mykiss,
by administration of emulsified buserelin (GnRHa) and its effects on egg
quality
M. Arabaci, I. Diler, M. Sari-2004
Aquaculture, 237(1-4): 475-484
Abstract:
The aim of this study was to evaluate the effects of
a water in oil (w/o) emulsion of the gonadotropin-releasing hormone agonist
buserelin ([
-Ser(tBu)6,Pro9-NEt]-GnRHa)
in Freund's incomplete adjuvant (GnRHa-FIA) on the induction and
synchronisation of ovulation in an early spawning strain (late
AugustSeptember) of rainbow trout, Oncorhynchus mykiss. Mature
females were injected once with 0, 25, 50 µg kg−1 of
GnRHa-FIA or 25 µg kg−1 of GnRHa in physiological saline
(acute treatment). All fish dosed with 50 µg kg−1 of
GnRHa-FIA ovulated within 10 days after injection, whereas fish dosed with
25 µg kg−1 of GnRHa-FIA reached 100% ovulation 13 days
after injection (water temperature, 11.5 °C). In contrast, ovulation
percentage was 71% in control group, but it was only 66% in fish treated
with acute injection of GnRHa 47 days after injection. Fertilization, eyeing
and hatching percentages were high in all treatment groups and did not
differ significantly among groups (p>0.05). None of the treatments
caused any prespawning mortality. However, post-spawning mortality was
observed in female rainbow trout treated with the low and high dose of
GnRHa-FIA (46% and 53%, respectively). In conclusion, both GnRHa-FIA doses
were effective in advancing the onset of ovulation, synchronising the
ovulation of the treated fish and shortening the reproductive period,
relative to the control or GnRHa injected group. GnRHa-FIA treatments did
not affect oocyte diameter or egg quality based on the fertilization, eyeing
and hatching percentages. There was, however, a very significant
post-spawning mortality, reaching 50% of the population.
(Fisheries Department, Agricultural Faculty, Yüzüncü
Yıl University, Campus-Van 65080, Turkey, e-mail: muhammet@operamail.com)
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