Summary:
The long-term effects of two salinities (15 and 27 ‰) on growth, feed conversion efficiency, and blood physiology of Atlantic halibut were investigated. Growth and feed conversion efficiency of juvenile Atlantic halibut was improved by 20% by rearing fish at intermediate salinities (here 15 ‰). Interestingly, the growth-enhancing effect of lowering the salinity seems to be independent of size and age of the halibut and is not reserved to the initial juvenile stage. A cost benefit analysis indicates that the new farming method has the potential to double the profit of a given halibut farm. Measured blood variables were lower at 15 ‰ compared with 27 ‰ while the values were within the range of that previously described and there were no indications that reduced salinities represented a stressful environment to the fish. Overall, the results indicate that the growth rate, feed conversion, and farming economics can be improved by rearing Atlantic halibut at near intermediate salinities.