Effects of prey density and temperature on survival, growth, and behaviour of newly hatched striped wolffish (Anarhichas lupus)

Abstract

Two of the main factors contributing to the growth and survival of larval fish are food and temperature. Adequate food must be provided when the larvae switch from endogenous to exogenous feeding. Temperature can affect growth rate, survival, and metabolism. Feeding and temperature studies were carried out on newly hatched striped wolffish (Anarhichas lupus). In a preliminary study larvae were fed three densities of Artemia, 100/1, 300/1, and 900/1. Survival was not significantly different among treatments (mean 19.5±5.78%) but growth rates were affected by prey density. A non-feeding study showed that larvae can survive on their yolk reserves for 2 to 4 weeks with the first mortality occurring at 15 days post-hatch. Larvae raised on a combination of Artemia and dry feed showed improved survival over the initial prey density study. The level of Artemia influenced growth, survival and weaning time. Final percent survival for larvae fed 900 Artemia/1 plus dry diet was 94.3% as compared to 52.6% for larvae fed 100 Artemia/1 plus a dry diet. Growth was also significantly faster for larvae fed at 900/1. Larvae offered a larger density of Artemia initially consumed more Artemia and weaned themselves onto dry feed two weeks earlier than larvae fed the smaller density of Artemia. Larvae were also raised at 3 different temperature regimes, high (8.0-13.5°C), low (4.0-7.8°C), and ambient (3.0-13.5°C). High temperature had the greatest effect on survival in the first 6 weeks. Survival levelled off after this time. Final survival for high, low, and ambient was 50.5%, 16.0%, and 6.8% respectively. Overall larvae grown at higher temperatures were larger than those at the lower temperature range. Specific growth rate however dropped at higher temperatures later in the study. -- The results of this experiment suggest that wolffish larvae should be fed a combination of Artemia and dry pellets immediately from hatch. Artemia should be continued until about 6 weeks or a length of 30 mm. At this time the larvae should be observed consuming primarily dry food. Temperature should be maintained at 4-8°C for the first 6 weeks. Evidence suggests that the temperature should not exceed 8°C after 6 weeks however further investigation is needed.