The development of bass, Dicentrarchus labrax, eggs in relation to temperature

Naturally spawned bass, Dicentrarchus labrax, eggs were incubated from fertilization at 15 temperatures from 6·8–20·6°C, and the developmental process was categorised into seven stages. Times from fertilization to the midpoints of each stage were calculated at each temperature. Knowledge of the developmental stage and incubation temperature was used to derive predictive relationships with which to age eggs. Minimum precision of age prediction was ±18 h. The first developmental stage was divided into six substages, and temperature-stage relationships derived to improve the precision of ageing to a minimum of ±1·75 h during early development. Bass eggs failed to hatch at temperatures below 9·7°C and above 16·8°C; this observation is discussed with reference to the developmental process.