Tolerance and growth of the longsnout seahorse Hippocampus reidi at different salinities

Abstract

Hippocampus reidi is one of the most popular seahorse species in the aquarium trade. The commercial breeding of this species is an alternative to reducing the fishing pressure on natural populations. Two experiments with newly born juveniles were conducted in this study to assess salinity tolerance (Lethal Time for 50% of the population-LT50), survival and growth during the first 10days of life. A third experiment determined the isosmotic point of adults. The highest LT50 was observed at 10psu, followed by 15, 20, 25, 30, and 35psu, and the lowest LT50 was recorded at 5psu. A negative relationship between salinity and final weight and between salinity and final height was observed through the regressions performed, such that a decrease in salinity (until the lowest level analysed; 10psu) implied a higher growth in height and weight. The highest survival rates were observed between the salinities 10 and 25psu. The isosmotic point of the species was determined at 11.68psu (303.38mOsm/kg), which is in agreement with the salinity where the best salinity results were observed in the first two experiments. Using an intermediate salinity to produce H. reidi on a commercial scale would be advantageous because of survival and growth improvement in addition to requiring a lower seawater uptake and less cost for purchase artificial salt.