This study is examining the effects of family, sex ratio, and ploidy on tolerance of rainbow trout to full strength seawater at variable temperature. Triploidy, characterized by three complete chromosome sets, renders fish sterile and offers advantages in net-pen production in Atlantic Canada, but triploids often have lower thermal tolerance than diploids. Conducted at the Huntsman Marine Science Centre (Saint Andrews, New Brunswick), this experiment used similarly sized fish from 48 mixed-sex diploid families, 15 all-female diploid families, and 12 all-female triploid families, with each fish individually PIT-tagged for tracking purposes. After a two-month freshwater acclimation period, fish were transitioned to seawater at ambient temperature (13±1°C). Temperature was then gradually increased to 21°C at 1°C per day, decreased and held at 18°C for 10 days, and finally decreased at 1°C per day back to ambient temperature (7±1°C).
Growth was assessed at three time points: PIT-tagging, 30 days after seawater entry, and at mortality or the end of the experiment. Initial mortality among all sizes was low after seawater entry but then increased as temperature rose (Figure 1). Statistical analysis of growth rates and survival by ploidy and family will be discussed.
This experiment seeks to evaluate the performance of sterile triploids under variable temperature conditions that may occur within marine net-pens, while also considering the potential to breed for improved performance based on family-level variations in response.