The influence of exposure to low temperature on Tilapia mossambica Peters (Cichlidae).

Abstract

In the cichlid teleost Tilapia mossambica secondary chill coma following exposure to 11° C in freshwater is associated with decreases in plasma osmolarity, sodium and chloride ion concentrations. Fish exposed in seawater diluted to give a NaCl concentration of 5%0 show no signs of coma nor are there decreases in osmolarity or sodium and chloride ion concentrations. It is suggested that the restrictions of T. mossambica to estuaries at the southern end of its distribution in southern Africa relates to the maintenance of near normal sodium and chloride ion concentrations at low temperatures during winter.