Growth, gonadal development and spawning time of Atlantic cod (Gadus morhua) reared under different photoperiods

摘要: Abstract Individually tagged Atlantic cod ( Gadus morhua L . ) (mean body weight 459±6 g) were reared in 20-m 3 tanks supplied with running sea water. During the first year fish exposed to one of four photoperiod regimes: Natural light (LDN), continuous from June 23, 1993 (LL), natural and December 22, (LDN/LL) or (LL/LDN). In July 1994, LDN LDN/LL groups terminated. The LL LL/LDN on until May 1995. From 1994 termination experiment 1995, group was under photoperiod. Cod spawned period between January April. Photoperiod manipulation changed incidence sexual maturation, spawning time, fecundity egg size. that transferred earlier, having lower smaller eggs than Oocytes females arrested cortical alveoli stage, even their second very few matured. When December, ovulated within 4–5 months, approximately months delayed compared group. These had a higher cod. for another these again next at normal e.g. 9 after spawning. pattern maturation influenced somatic growth pattern. Differences explained by differences timing relative investment. At an age 26 1.5 2.5 kg, respectively. this, it is concluded reduction daylength vital environmental signal regulating cod, may be considerably its absence.