Meso- and bathypelagic fish feeding ecology: A meta-analysis on fatty acids and stable isotope trophic studies

Recent studies suggest that the global biomass of fish in the ocean is dominated by meso- and bathypelagic fish. However, despite their abundance and important role in marine ecosystems, their trophic ecology remains poorly understood. Feeding studies of meso-/bathypelagic fish are temporally and geographically scattered and apply different methodologies. A meta-analysis of published fatty acid and stable isotope data was conducted to determine the diet patterns of 23 meso-/bathypelagic fish species. The dataset was processed using logratio analysis resulting in a set of six biochemically important logratios which explained 91.5% of the total variance. The results demonstrate a gradient of feeding strategies from trophic level 2.17–3.38 and interspecific variation in the content of key fatty acid trophic markers indicated a potential gradient of meso-/bathypelagic consumers of herbivorous to carnivorous prey. Stable isotope analysis showed statistically significant differences in isotopic values of fish sampled in different locations and characterized by different fatty acid trophic markers, whereas trophic diversity and redundancy were explored based on six community metrics. Our study serves as a global perspective on the trophic ecology of meso-/bathypelagic fish based on currently available biochemical data. This type of studies, derived from the combination of fatty acid and stable isotope analyses could potentially be useful in large-scale comparisons of meso-/bathypelagic fish trophic ecology studies and that would ultimately better define their function in the global oceanic ecosystem. •Parallel analyses of stable isotopes and fatty acids decipher the deep-sea fish diet.•Log-ratio analysis addresses the fatty acid datasets sub-compositional incoherence.•Community metrics facilitate interpretation of isotopic niche and trophic diversity.•Large-scale analyses account for the feeding ecology of fish with unknown diet.