Coping with multiple stressors: physiological mechanisms and strategies in fishes of the Salton Sea

Abstract

Saline lakes are found around the world, typically within inland drainage basins that lack outflow. While fish species in these lakes are not numerous, the Salton Sea in southeastern California, USA, supports several species and a substantial recreational fishery. The Salton Sea was formed in 1905, and since its formation, the salinity has varied greatly, and is currently approaching 44 g/l. The Salton Sea presents several environmental challenges to fishes that inhabit it, especially high salinity, large variations in temperature, and high levels of calcium and sulphate. Studies investigating the osmoregulatory ability of the California Mozambique tilapia (Oreochromis mossambicus x O. urolepis hornorum), the dominant species in the Salton Sea, indicate that they can tolerate salinities up to 65 g/l at 25 °C with minimal effects on osmoregulatory status. However, a reduction in temperature to 15 °C or an increase to 35 °C (both within the range of temperature observed in the Salton Sea) greatly reduce the salinity tolerance of this species. These data indicate that the seasonal winter kills of California Mozambique tilapia are likely associated with a direct effect of temperature on salinity tolerance at the current salinity of the Salton Sea. In this review we explore these environmental stressors and their effects on fish, particularly within the context of the Salton Sea fishery, and discuss how euryhalinity may give tilapia an advantage over the other Salton Sea species with respect to surviving the dynamic environment.