Thermal effects on growth and time to starvation during the yolk-sac larval period of Atlantic mackerel Scomber scombrus L.

The effect of incubation temperature (8·6, 11·1, 13·2, 15·1 and 16·8° C) on north-east Atlantic mackerel Scomber scombrus development, growth and age at starvation during the yolk-sac larval period was investigated. Standard length at hatch was found to be inversely proportional to incubation temperatures within the natural thermal ranges of this species; it ranged from 3·76 mm at 11·1° C to 3·30 mm at 17·8° C. Following hatch, however, larval growth rate was positively related to temperature. Individual logistic models, as a function of temperature and age, were fitted to the development processes of gape, eye pigmentation, jaw mobility and yolk exhaustion. Thereafter, development was classified into different ordered stages and an extended continuation model was fitted to the multinomial ordered stage classification. In all cases, there was a difference of >23 h between the first and the last individual developing in certain stage. The probability of survival decreased with age and was inversely related to temperature. Yolk utilization varied from 4·5 to 8·6 days and individuals died between 7·9 and 12·2 days from 17·8 to 11·1° C. The study demonstrated the significant impact that temperature has on development, growth and survival rates, during the early life history.