Triploid salmonids are used in aquaculture and stocking programs for recreational fishing because they are reproductively sterile and therefore cannot breed in the wild. However, they appear to be more sensitive than diploids to hypoxia and high temperature stress. The objective of my MSc is to develop a better understanding of the biological requirements of triploids (specifically hypoxia tolerance), with the potential to improve triploid performance.
I compared the acute hypoxia tolerance of sibling diploid and triploid brook charr that were acclimated to either moderate hypoxia (dissolved oxygen at 70% air saturation) or normoxia (100% air saturation) for 7 weeks. Fish then underwent acute hypoxia trials, by slowly injecting nitrogen gas to displace oxygen and using loss of equilibrium (LOE) as the endpoint. Dissolved oxygen levels at LOE (later converted to oxygen tension; kPa), and time to LOE were recorded for each individual fish. Following LOE, all fish were measured (fork length and body mass) and a blood sample was taken. Fish were then euthanized and dissected to remove the whole heart, the ventricle, the liver, the gills, and the gonads. I used the body measurements, blood, and tissue samples to determine condition factor, hematocrit, whole blood glucose and lactate levels, plasma ion concentrations and osmolality, interlamellar cell mass size, relative ventricular mass, compact myocardium thickness, hepatosomatic index and gonadosomatic index. Hypoxia-acclimated fish had a higher tolerance for hypoxic conditions, as indicated by a longer time to LOE and a lower PO2 at LOE compared to fish acclimated to normoxia, but there was no effect of ploidy on hypoxia tolerance.
Funding acknowledgement: NSERC (Discovery Grant), Mitacs (Research Training Award), NBIF (Research Assistantships Initiative), and UNB (graduate research assistantships).