Journal of Aquaculture Research & Development

Stocking density limits for post-smolt Atlantic salmon (Salmo salar L.) in semi-closed sea systems

International Conference on Aquaculture & Fisheries

July 20-22, 2015 Brisbane, Australia

Sara Calabrese

Posters-Accepted Abstracts: J Aquac Res Development

Abstract:

For the development of commercial scale semi-closed sea systems for post-smolt Atlantic salmon, further knowledge is required on the biological limits for fish density. In this experiment post-smolts were stocked in 5 different densities (25, 50, 75, 100 and 125 kg/m3) for 8 weeks in 10°C seawater. Water quality parameters such as oxygen, pH, CO2 and TAN were monitored and kept within recommended values. The biomass in each tank was weighed every second week and increases in biomass were removed to maintain original treatment density throughout the experiment. Over the 8 week period the specific growth rate (SGR) of the biomass was reduced in densities above 75 kg/m3, furthermore when densities were increased from 100 kg/m3 to 125 kg/m3 growth rate decreased by 47%, along with a reduction in feed utilization. The effect of stocking density on post-smolt welfare was determined by studying the overall stress response and by examining external morphological welfare indicators. After 8 weeks primary and secondary stress responses such as elevated plasma levels of cortisol, blood sodium, PCO2 and decreased blood pH were observed in the highest stocking density. Fish densities above 75 kg/m3 also increased pelvic fin damage and the prevalence of cataracts. In conclusion, this study suggests that stocking density should not exceed 75 kg/m3 in order to maintain optimal post-smolt performance and welfare. These results will have important implications for the design and development of commercial scale semi-closed sea systems.