Polyunsaturated Fatty Acid Content in the Muscles of Alien Fish Species of the Rybinsk Reservoir

The biochemical composition of the muscles of two fish species, European smelt Osmerus eperlanus and the Common (Caspian) kilka Clupeonella cultriventris, that were successively invaded and naturalized in the Rybinsk Reservoir in the second half of the 20th century, differs significantly in the fatty acid content. The sum content (mg/g) of eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) polyunsaturated fatty acids in the muscle tissue of the kilka is almost four times higher than that in European smelt. Given that smelt and the kilka are similar in their ecological and morphological characteristics and do not differ significantly in the composition of their diet in the Rybinsk Reservoir, it is obvious that the observed differences primarily result from the phylogenetic aspect. The obtained data on the composition of the fatty acids of the invaders show that the replacement of one alien species with another (European smelt with the kilka) significantly changed the quality of production of an important link in the trophic web of the reservoir.