Environmentally adjusted reproductive strategies in females of the commercially exploited common squid Loligo vulgaris

Abstract

Loligo vulgaris is the most abundant and commercially important species of squid in Portuguese waters. The species presents a complex population structure due to a short life-cycle, highly variable growth rates and a long spawning period. The latter characteristics combined with the marked seasonality of the Portuguese coast results in individuals that are born in different seasons being influenced by different environmental conditions, notably water temperature, as has previously been shown. In the present study, we have taken animals belonging to each of two temperature-based hatching cohorts (cold and warm cohorts – CC and WC) and determined the fecundity and egg size of individuals on either one, in order to determine whether animals in different cohorts followed different reproductive strategies. Significant differences were found between the cohorts regarding reproductive investment, fecundity and size of oocytes. Individuals of the CC (larger and older when reaching maturity) had lower fecundity than individuals of the WC, but presented larger oocytes. WC females (smaller and younger at maturity) present higher fecundities and higher GSIs. Such differences further demonstrate the high plasticity and adaptability of these organisms to environmental conditions and highlight the advantage of integrating environmental variables in fisheries assessment.