Lacustrine fishes and the trophic efficiency of lakes:: prelude to the problem

The regression between the yield of fish (Y) and the mean annual temperature of air (TEMP) both for geologically old lakes with endemic lacustrine fish fauna and those of the relatively recent origin inhabited by riverine species is the same. In contrast, the dependence of Y on the morphoedaphic index (MEI) in lakes with endemic lacustrine fish species differs strongly from that for lakes with riverine fish communities giving the predicted Y about three times higher for the former in comparison with that of the latter. The higher trophic efficiency of ancient lakes with endemic fish faunas is a consequence of the presence of pelagic species. Contrary to this, recent lakes are inhabited with riverine species dwelling along the shores leaving pelagic niche unoccupied.