Fatty acid analyses reveal differences in feeding ecology of North Sea squids that overlap in time and space

Climate-induced changes in marine ecosystems have been documented worldwide. As one of the main consequences, a shift in the distribution of species is observable in many marine areas, resulting in the formation of new species communities and new interactions. In the North Sea, the squid community has changed considerably over the last 100 years. Some species have disapeared while new species have established and are now living in coexistence in a new community. Although squids are considered to be predators that feed rather non-selectively, we aimed to answer the question of whether their diet differs nevertheless. Therefore, we analysed the fatty acids of three squid species whose distribution substantially overlaps. We were able to recognise a dependence between the size of the squid and the composition of fatty acids and are able to demonstrate the already known ontogenetic shift in food composition on the basis of fatty acid composition. Furthermore, we illustrate that the fatty acid composition differs significantly between squid species, which points to different prey of the analysed squid species and which may be one reason for their successful coexistence.