The salinity tolerance of Pseudophoxinus stymphalicus (Cyprinidae) and Valencia letourneuxi (Valenciidae) from western Greece suggests a revision of the ecological categories of freshwater fishes

The salinity tolerance of two common teleosts from Greece, one a primary division species, Pseudophoxinus stymphalicus, the other a secondary division species, Valencia letourneuxi, was evaluated in laboratory studies. Experimental subjects were acclimated to a salinity of 6ppt. Through gradual increases, individuals of P. stymphalicus were able to tolerate salinities up to 12-13ppt, while individuals of V. letourneuxi survived in normal seawater (33ppt) and had an upper lethal limit of ca. 46ppt. Valencia letourneuxi, one of two species of the Mediterranean family Valenciidae, is one of the least euryhaline of secondary division teleost fishes. Its distribution matches that of P. stymphalicus, suggesting that its dispersion was not by way of marine waters but by mechanisms used by primary and primary-like freshwater fishes. We reconsider the primary and secondary division and primary-like categories and propose that five basic groups be recognized: primary, primary-like, secondary low salt tolerant, secondary high salt tolerant, and peripheral.