Effects of body weight at hatching and water temperature on development of the yolk-sac larvae of six species of salmonids, including grayling

Abstract

The effects of larval weight on survival and growth were studied at a range of temperatures for four species of fish that are native to Austria, and two introduced species. Spawning times differ, and the thermal requirements for embryos and larvae reflect the temperatures of adaptation to their habitats. Optimum temperatures for hatching success are compared with optima for larval survival; the ranges of temperatures at which at least 50 % of larvae survived are wider than those for hatching, suggesting that temperature requirements can alter in different life-stages. Most of the variation in larval fresh weight with time was attributed to temperature, although size at hatching can also have an effect. In the temperature range 4 °C to 20 °C, the overall weight gains of the six species differed between 3.7 mg to 52.6 mg, with growth rates of 17 % to 431 % and maximum body weights between 16.3 mg and 118.4 mg. A series of relatively simple models can be used for predicting parts of the life-spans, e.g. length of the embryonic development and yolk-sac larval stages, and mean weights of each species, from fertilization of the egg to the end of the larval stage. Studies of early life stages are becoming increasingly important in forecasting recruitment of wild fish. In cultured fish the yolk-feeding stages are central to success or failure of larviculture.