Indices of hydromineral metabolism in tyulka (Clupeonella cultriventris; Clupeiformes, Clupeidae) introduced in the Rybinsk Reservoir in comparison to aboriginal and marine fish species

Abstract

The parameters of hydromineral exchange and the upper limit of salinity within the historical range of tyulka are typical of stenohaline freshwater fishes. These features assume freshwater origin of this species. Compared to the aboriginal species, tyulka introduced and established in the Rybinsk Reservoir has a higher level of potassium in the plasma, lower contents of water and potassium in muscles, lower content of calcium in erythrocytes, and lower contents of magnesium in plasma, erythrocytes, and muscles. High levels of sodium in the tyulka erythrocytes reflect elevated oxygen-carrying capacity of blood, indicating increased oxygen demand of this species. The content of magnesium in the tyulka erythrocytes is 2–3.7 times lower than in the indigenous species. This shows lower affinity of hemoglobin to oxygen in tyulka. The study reveals that strong external impacts are accompanied by very fast desalination of tyulka blood. In turn, this determines increased vulnerability to unfavorable environmental factors.