Importance of parental effects on larval survival in Sardina pilchardus

A combined field and laboratory study was carried out to determine the importance of parental effects (spatial and temporal variations in spawning, egg size and biochemical composition of the egg) on larval survival in Sardina pilchardus, Egg abundance was positively correlated with the seston organic content (SOC; a combination of total protein, carbohydrate and lipid content) of the size particle fraction 20 to 1000 mum. This was interpreted as a reproductive strategy, to spawn more eggs in areas and during periods of enhanced food availability to larvae. Larval survival under starvation conditions was related to temperature, but only when just the larvae in which the yolk-sac was fully absorbed at death were considered. However, if larval survival time was estimated considering all larvae, including those which died before yolk-sac absorption, larval survival time was related to the biochemical composition of the egg. Larval survival time increased as the percentage of protein in the egg increased, indicating the importance of protein under food limiting conditions. Furthermore, percentage of larvae with yolk-sac completely absorbed at death was higher as egg protein percentage increased. Although producing eggs with a higher proportion of proteins in response to diminishing food availability could maximise larval success under starvation conditions this parental strategy was not exhibited by S. pilchardus. There was not a significant relationship between egg protein percentage and SOC. Biochemical composition of the egg seemed to vary according to temperature of the water.