Seasonal variability of maternal effects in European hake Merluccius merluccius

Abstract

Maternal attributes may influence the quantity and quality of offspring and hence, their survival. We evaluated the seasonal variability in maternal effects on developing oocytes and larvae of European hake Merluccius merluccius from the southern stock. Females were collected in 10 different years between 1999 and 2017 in the 3 spawning seasons identified in NW Spain (winter-spring, summer and autumn). Five indices of reproductive trait characteristics (batch fecundity [BF], relative fecundity [RBF], oocyte dry weight [ODW], oocyte diameter [OD] and oocyte lipid droplet diameter [ODD]) and 4 indices of maternal effects (total length [TL], gutted weight, hepatosomatic index [HSI] and Fulton's K) were analysed. Additionally, larvae were sampled in 2017 during winter-spring and summer spawning peaks to study seasonal variability in their growth and allometry. The results revealed maternal effects on offspring attributes (for both oocytes and larvae) that differed among seasons in terms of productivity and oocyte quality; more and likely better-quality oocytes were produced in the winter-spring. BF, ODW and OD were influenced mostly by female size, ODD was related to HSI, and RBF was not influenced by any maternal attribute. The larval growth rate was similar, although summer larvae had more developed anterior body parts than winter-spring larvae. The temporal differences could be due to differences in maternal attributes and/or environmental conditions; these differences might impact larval survival and hence annual stock recruitment. A multi-year analysis of interactions between environmental conditions and maternal effects is required to understand the complex process of larval recruitment.