| Summary: | In salmon aquaculture, fish occasionally escape from net pens. These domesticated salmon are genetically maladapted for living in natural environments however they still manage to interbreed with wild fish, resulting in severe levels of genetic introgression of farmed salmon in some Norwegian rivers. The use of sterile triploid farmed salmon, with three complete chromosome sets, would avoid further genetic introgression. Initial studies comparing diploids and triploids show reduced performance and higher mortality of triploid salmon that impeded their adoption to commercial farming. With advances in fish husbandry and further knowledge on triploid salmon biology, some of the farming related issues have been mitigated. However, to date, there are still challenges remaining in order to farm triploid Atlantic salmon profitably, sustainably and without jeopardizing fish welfare. Triploids perform poorly at high water temperatures and hypoxic periods, often associated with reduced growth and higher mortality compared to diploids. Further, triploid Atlantic salmon are more prone to develop ocular cataracts that can affect vision, feed intake and welfare. Additional supplementation of the amino acid histidine to the diet successfully mitigated cataract outbreaks and progression in diploid Atlantic salmon. However, the interactive effect between water temperature and dietary histidine level on cataract development in triploid salmon during the risk period of smoltification has not been studied. In order to investigate the temperature threshold for satisfactory performance and the physiological mechanisms behind reduced or poor performance at suboptimal environmental conditions, diploid and triploid Atlantic salmon post-smolts and adult fish were exposed to water temperatures between 3 and 18 °C (3 °C steps) and to hypoxic periods at cold (6 °C) and warm (18 °C) temperatures. Feed intake, growth and mortality were monitored as well as oxygen consumption, white muscle energy phosphate and carbohydrate storages, blood ...
|
|---|