Reproduction, condition and abundance of the Mediterranean bluefish (Pomatomus saltatrix) in the context of sea warming

Abstract

This study evaluates the link between sea warming and three important aspects of the population dynamics of bluefish, Pomatomus saltatrix, in the NW Mediterranean: condition (health measures), reproduction and abundance (as reflected in catch per unit effort, CPUE). We compared the bluefish populations from two areas with different thermal regimes: the Gulf of Roses and the Ebre Delta. First, in order to compare the condition and reproduction parameters of the two populations, specimens were collected from the commercial catch landed in two ports located in these areas. Several indicators of fish condition and reproduction such as hepatosomatic index, gonadosomatic index, maturation timing, length-at-first maturity, fecundity, egg quality and atresia (ovarian follicle resorption) were analysed and compared between study areas. Secondly, time series analyses of sea surface temperatures (SST) and monthly bluefish CPUEs in the two study areas were assessed using Box-Jenkins transfer function models. Our results indicate that bluefish benefit from sea warming in the NW Mediterranean, particularly in the northernmost zone, as evidenced by increasing fish condition in these waters. Sea warming may favour the changes in spawning phenology and the northward expansion of this species. This study provides evidence that a marine fish species that is able to expand or it is forced to shift its distribution due to sea warming, may take advantage of other environmental conditions of new habitats, contributing to the enhancement of the population's productivity in these areas