Maternal influences on egg and larval characteristics of plaice (Pleuronectes platessa L.)

Maternal influences on various egg and larval characteristics were examined using plaice from the Irish Sea and Norwegian coastal waters. Thirty-nine batches of eggs were incubated during the spawning season of 2004 and 2005. Thirty-seven larvae from one batch were also monitored individually to examine the influence of egg size on larval size at hatching, yolk sac volume and growth at the individual level. The relationship between egg dry weight (EDW) and egg diameter (ED) differed between the fish from different origins. Egg size increased with maternal size and decreased with progression through spawning. Eggs from the Norwegian coast hatched on average two days earlier than eggs from the Irish Sea. This resulted in the larvae from the Norwegian coast hatching at a smaller size and with larger yolk sac volumes. Larger eggs gave rise to larvae with larger yolk sac volumes at hatching (independent of incubation period) both at the batch and individual level. Larval growth rate was influenced by larval hatching size and yolk sac volume with smaller larvae and larvae with larger yolk sacs having a greater growth rate between hatching and two weeks after hatching. The effects of egg size on larval plaice were present until the end of the yolk sac stage due to differences in the time taken to absorb the yolk sac. Neither hatching rate, age at first feeding nor larval survival was related to maternal size or egg dry weight.