Publication Abstract

The influence of feeding regime on sexual maturation, fecundity and atresia in first time spawning turbot (Scophthalmus maximus L.)

The influence of feeding regime on sexual maturation, fecundity and atresia in first time spawning turbot (Scophthalmus maximus L.)

P.J. Bromley, C. Ravier and P. Witthames

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.

The provision of possible management measures, such as the implementation of temporary closed areas, to protect pre-recruit 0-group gadoids on settlement sites is discussed.

Reference:

P.J. Bromley, C. Ravier and P. Witthames, 2000. The influence of feeding regime on sexual maturation, fecundity and atresia in first time spawning turbot (Scophthalmus maximus L.). Journal of Fish Biology, 56: 264-278

P.J. Bromley*, C. Ravier and P. Witthames*

Journal of Fish Biology, 56: 264-278