Content of highly unsaturated fatty acids in fish from rivers of contrasting temperature

Abstract

AbstractContents of highly unsaturated long‐chain fatty acids of omega‐3 family (HUFA); eicosapentaenoic acid (EPA; 20:5n‐3); and docosahexaenoic acid (DHA; 22:6n‐3) are the principal indicators of the nutritive quality of fish for humans. Effects of environmental factors, first of all water temperature, on EPA and DHA contents in fish tissue are not currently completely understood. To reveal the putative effect of water temperature, fatty acid composition and contents were studied for 6 fish species, inhabiting the cold waters of the Yenisei River (Siberia, Russia) downstream of a dam (hypolimnetic release from reservoir) and its adjacent warm water tributaries (the Mana River and the Kacha River). It was hypothesized that (a) fish species from the cold river would have higher HUFA contents than fish from the warm rivers and (b) temperature would be negatively correlated with HUFA content in fish species. Using gas chromatography–mass spectrometry, distinct species‐specific fatty acid profiles were observed, whereas contents of the essential fatty acids, EPA and DHA, in fish species from the cold Yenisei River were in general similar to that from warm tributaries. Thus, in contrast to the first hypothesis, phylogenetic factors overweighed the effect of water temperature and food (benthic invertebrate) composition, on fatty acid composition and HUFA content in fish. For the second hypothesis, for the 2 species inhabiting both cold and warm rivers, only one had higher EPA and DHA content at lower temperatures. Consequently, the response of EPA and DHA content in fish tissue to temperature variations may be species‐specific.