Maternal effects on egg and larval size of european hake in the Galician shelf

Abstract

Maternal effects, environmental conditions and their interaction can influence size and condition of larvae, ultimately affecting their survival. This study aims to analyse maternal effects on European hake larval size from the Southern stock during the two main spawning peaks along the year (winter-spring and summer) in the Galician shelf (NW Spain). Actively spawning females (and their hydrated eggs) were sampled on a monthly basis from commercial fishing landings and larval samples were collected during two oceanographic surveys in March and June in 2017. Larval growth and morphometry were also analysed for each period. Results showed that spawning females were bigger and heavier during winter-spring period than in summer, but condition indices did not differ significantly between spawning periods. Eggs were significantly bigger in terms of diameter and dry weight (in association with female traits) in winter-spring than in summer, while egg oil droplets resulted smaller. However, standard length at hatch presented significant differences between periods, being 200 μm bigger in summer than in winter-spring even when the first increment of the otolith and larval growth rate were similar. Moreover, larvae from winter-spring period hatched shorter but wider while larvae from summer were larger and thinner. Then, results suggest that maternal effects are stronger and different in eggs than in larval stage. This study disagrees with the current unifying theory which suggests that larger eggs result in large larvae. In fact, size of European hake larvae may be more related with egg condition (determined by oil droplet size) than egg size. Differences among periods can be produced not only by maternal effects, it can also be an adaptation to environmental conditions of each period. Even that, this analysis should be integrated with environmental conditions to understand the complex process of larval recruitment