Ecological energetics of pelagic fish of the Mediterranean Sea: interspecific and seasonal differences

The 3rd CLIOTOP Symposium,14-18 September 2015, San Sebastian, SpainSmall and Medium Pelagic Fish (SMPF) have a very important role as a food source for upper trophic level predators. The quality of prey fish has important effects on the consumers, influencing growth rates, survival and reproduction of predators. However, knowledge on prey energy content is scarce and usually estimates of this parameter are used. Therefore, our aim was to analyze the energetic content of seven SMPF species (Engraulis encrasicolus, Sardina pilchardus, Sardinella aurita, Trachurus trachurus, Trachurus mediterraneus, Scomber scombrus and Scomber colias), that are ecologically important and present a high biomass in the western Mediterranean. Specifically, ten adult individuals of each species were sampled each season through one year to analyze the energetic content using direct calorimetry. Moreover, other condition parameters were measured. We discuss the variation of energy content between species and within species in the annual cycle and its implications for upper trophic level predators. As it was expected, there were significant differences in the energetic content of each species between seasons, mainly depending on the maturity stage. Moreover, combining the energy density results with the gonadosomatic index, we were able to define the potential reproductive strategy (income or capital breeder) for each species. Between species, there were significant differences in energy density, highlighting the importance of using species specific parameters in the bioenergetics ecosystem models. These results provide new insights in the energy content of important prey species in the pelagic ecosystem, information that is important in order to understand the dynamics and energy transfer between different trophic levelsPeer Reviewe