Salinity tolerance of the eggs and larvae of the Australian grayling, Prototroctes maraena Gnnther (Salmoniformes : Prototroctidae)

Abstract

Eggs of the Australian grayling Prototroctes maraena were fertilized in the laboratory and the survival of eggs and larvae was investigated in salinities ranging from <0.1 to 30 g L^-1. In salinities of <0.1, 5, 10 and 15 g L^-1, most (81-90%) eggs survived to hatching; in salinities of 20, 25 and 30 g L^-1, all eggs died. In salinities of <0.1 and 5 g L^-1, all eggs that survived developed normally and the larvae survived for 21 d. In a salinity of 10 g L^-1, all eggs that survived developed normally but the larvae were inactive and died within 6 h. In a salinity of 15 g L^-1, many larvae were unable to emerge completely from the egg, were grossly deformed and died within 1 h of hatching. Newly hatched larvae were buoyant, positively phototropic and swam actively near the water surface. They survived in salinities ranging from <0.1 to 30 g L^-1 for 21 d, at which time yolk absorption was complete. Death was probably the result of starvation.