THE INFLUENCE OF FEEDING REGIME ON SEXUAL MATURATION, FECUNDITY AND ATRESIA IN FIRST-TIME SPAWNING TURBOT
P. J. Bromley, C. Ravier, P. R. Witthames -2000
Journal of Fish Biology, 56 (2): 264-278
Abstract:
Exposure of adolescent turbot Scophthalmus maximus to low rations
during vitellogenesis, covering the 4 months immediately prior to
spawning, led to a drop of 70% in mean ovary weight, and was associated
with poor growth of the vitellogenic oocytes or, in a third of cases, the
absence of vitellogenic oocytes. Exposure to low rations during the
recruitment of vitellogenic oocytes, 4-8 months prior to spawning,
produced a more variable response. A few of these females produced
well-developed vitellogenic oocytes, but in most, vitellogenic oocytes
were absent or only poorly developed and in some cases there was a high
incidence of atresia. Exposure to intermediate rations throughout oocyte
recruitment and vitellogenesis also depressed oocyte development. In
maturing females the number of non-atretic vitellogenic oocytes (relative
potential fecundity) averaged 998 per g of somatic body weight of fish at
the start of the spawning season in mid-June. Maturation of the males was
not significantly influenced by the dietary regime. The small size of the
testes and the low levels of milt production, even in fish fed high
rations immediately prior to spawning, showed that reproductive investment
in males was much lower than in females.
(CEFAS, The Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk, NR33 0HT, UK)
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