Survival and growth of all-female diploid and triploid rainbow trout ( Oncorhynchus mykiss) reared at chronic high temperature

Abstract

The salmonid aquaculture industry has recently been investigating the benefits and drawbacks of sterile triploids. Although studies have shown that triploids should not be restricted by their altered haematology under optimal conditions, little is known about their performance in sub-optimal environments. This study focused on the performance (in terms of growth and survival) of female triploid rainbow trout ( Oncorhynchus mykiss) in comparison to female diploids at chronic high temperature. Triploid and diploid rainbow trout were reared in fibreglass tanks at 21 ± 1 °C for 23 days. At these chronic high temperatures, triploids had a significantly ( P < 0.001) higher mortality rate in comparisons to diploids: 68.5% of the triploids ( n = 175) died within 3 weeks at 21 ° C, while only 39% of the diploids ( n = 167) died in this time period. Diploids had larger fork lengths (by 4.8%), body weights (by 23.9%) and condition factors (by 10.3%) than the triploids by the end of the experiment ( P < 0.05 in all cases). The cause of fish mortality in this experiment was likely to be multifaceted, and influenced, and/or directly caused, by the stress of the experimental protocol. However, it is evident from these results that triploid rainbow trout did not survive or grow as well as diploids in chronic high water temperature conditions.