Feeding ecology of Sardina pilchardus considering co-occurring small pelagic fish in the eastern Adriatic Sea

Abstract

Small pelagic fish with their significant biomass are connecting plankton production and higher trophic levels in marine ecosystems. The aim of this paper was to analyse feeding habits of sardine Sardina pilchardus (Walbaum, 1792), regarding the season and the spatial area, but also considering trophodynamics of other co-occurring small pelagic fish: anchovy Engraulis encrasicolus (Linnaeus, 1758), round sardinella Sardinella aurita (Valenciennes, 1847), chub mackerel Scomber japonicus (Houttuyn, 1782) and horse mackerel Trachurus trachurus (Linnaeus, 1758) in the eastern Adriatic Sea. Sardine revealed copepods (average contribution 30%), decapod larvae (18%), mysids (15%) and copepod eggs (9%) as their main source of energy. Seasonal oscillations of the sardine fullness index were determined, with highest values in the autumn and spring (%Jr = 0.71 and 0.66, respectively). Spatial analysis showed no significant difference in the diet of fish caught in offshore and coastal waters (ANOSIM, Global r = 0.034; p > 0.05). The ANOSIM test showed a significant difference in prey composition among five investigated species (Global r = 0.081, p < 0.05). The greatest difference in diet was observed between sardine and chub mackerel, as well as between sardine and horse mackerel. While copepods dominated in the sardine, anchovy and round sardinella stomach, horse mackerel and chub mackerel showed selectivity for larger prey as euphausiids, which dominated in terms of numbers, while the most frequent prey were decapod larvae. However, calanoid copepods, fish larvae, decapod larvae, decapod larvae–megalopa stage, copepod eggs, amphipods and isopods were present in the diet of all small pelagic fish. Interspecies diet overlap, besides being significant for marine food web modelling, is particularly important for future fishery management, since investigations in this field are still mostly based on a single-species diet approach.