Egg size variability and mating system in the marbled goby Pomatoschistus marmoratus (Pisces : Gobiidae)

The marbled goby Pomatoschistus marmoratus inhabits the Venetian lagoon, northern Adriatic Sea. We used both field and laboratory approaches to investigate the mating system and factors influencing egg size and number. Males nest in empty bivalve shells and provide parental care to eggs. Egg size showed wide variation (CV = 11.5 %) and was positively correlated with female size and parental male size, but negatively with the progression of the spawning season, Field data showed that larger males occupied larger nests and obtained more and larger eggs than smaller males, Laboratory experiments showed that larger females produced both more and larger eggs than smaller ones. The relationship between egg size and male and female sizes suggested the presence of size-assortative mating in this species. The presence of high environmental variability could select for the peculiar pattern of egg size variability observed in this population.