Effects of Temperature and Salinity on Early Ontogeny of Bigmouth Sleeper Larvae

Abstract

AbstractDeclines in the abundance of Bigmouth Sleeper Gobiomorus dormitor within its range warrant directed conservation efforts, which may include population supplementation with hatchery‐produced fish. However, previous attempts at Bigmouth Sleeper culture resulted in limited larval development and lack of successful exogenous feeding after yolk sac depletion, presumably in response to environmental conditions. The effects of temperature and salinity on hatch success, survival, growth, and development of Bigmouth Sleeper yolk sac larvae were examined in controlled, replicated experiments. Hatch success was greater at lower temperatures (23°C) and salinities (0, 5, and 10 g/L), larvae survived longer at lower temperatures (23 and 26°C), and growth metrics were greatest in freshwater (salinity = 0 g/L). Larvae held at salinities of 5 g/L and higher experienced 100% mortality within 12 h posthatch. Survival and development were inversely correlated and dependent on temperature; survival was greater at 23°C, but larvae developed slowly, while development was rapid at 29°C, yet all fish died by 48 h posthatch. The results suggests that the optimal hatching temperature and salinity for Bigmouth Sleeper is 23°C and 0 g/L, respectively, and the optimum rearing temperature for yolk sac larvae is 26°C. However, the amphidromous life history strategy of this species may require an increasing temperature and salinity regimen that mimics the environmental conditions larvae would experience following hatch during downstream transport from cooler freshwater streams to warmer brackish and marine waters in their natural habitats.