Effects of environmental condition on growth and reproduction of atlantic cod, Gadus morhua
2006
Yoneda, M.(Tohoku National Fisheries Research Inst., Shiogama, Miyagi (Japan))
This paper describes the effects of temperature and food availability on growth and reproduction of first-time spawning Atlantic cod, Gadus morhua, in addition to the previous findings on the relationship between environmental condition and reproductive characteristics of this species. A reduction in daylength is a vital environmental cue regulating the gonadal maturation. The growth in vitellogenic oocyte diameter is positively correlated with temperature. Higher food availability can lead to a higher egg production of females that have experienced spawning before. In first-time spawning fish, there were sex-specific differences in the environmental effects on sexual maturation and gamete production. Low temperature led to an arrest in the onset of vitellogenesis, resulting in the occurrence of females that postponed spawning. Food manipulation did not significantly affect potential fecundity, but did affect somatic growth during vitellogenesis. In contrast, higher food availability resulted in a higher sperm production. A marked truncation in the upper size and age structure of cod spawning stock biomass is now evident due to the intense fishing pressure during the last several decades. Therefore, the pre-spawning season environment could potentially have an effect on annual egg production of such young population in the coming and future spawning seasons.
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