Seasonal fatty acid profile analysis to trace origin of food sources of four commercially important bivalves

Knowledge of bivalve food sources has great importance in aquaculture areas where cultured species usually occur at higher densities than in natural populations. Except phytoplankton, which is considered as their primary food sources, bivalves can use other food sources such as detritus, bacteria and zooplankton. The objective of this study was to determine food sources of four commercially important bivalve species co-existing in the Mali Ston Bay - most important aquaculture area of the eastern Adriatic Sea. Food sources were investigated by analyzing the fatty acid profiles of digestive gland and muscle tissues of the European flat oyster Ostrea edulis and the black mussel Mytilus galloprovincialis, cultured in the water column, and the bearded horse mussel Modiolus barbatu.s and Noah's ark shell Arca noae from natural populations. Digestive gland fatty acid analysis revealed that during the period of higher plankton abundance in spring and summer, all species ingested mainly phytoplankton followed by zooplankton and detritus. During the low plankton abundance of the autumn-winter period zooplankton and/or detritus became more important in a bivalve diet. Fatty acid composition of muscles indicated differences in selective incorporation of polyunsaturated fatty acid (PUFA) from their diets. While A. noae and M. barbatus accumulated significantly PUFAs during all and O. edulis during spring-summer period, in M. galloprovincialis this tendency was not observed at all. This suggested better utilization of ingested food in bottom-dwelling species. Because all four species consumed similar food sources they were in competition. However, as investigated species in Mali Ston Bay exist in high density, primary production plus the availability of other food sources in this area was probably sufficient to satisfy demands for all species. Aquaculture in the study area depends wholly on natural spat. This suggests that larviphagy, observed for all species, might constitute a self-regulating restriction to natural populations and/or commercial aquaculture growth. (C) 2011 Elsevier B.V. All rights reserved.