The effects of temperature, egg quality and nutrition on the early development of triploid Atlantic salmon (Salmo salar L.)

Abstract

This thesis has successfully advanced understanding regarding potentially sub-optimal early life stage triploid culture. Further investigation of egg incubation temperature requirements elucidated that a constant temperature of 6 °C from fertilisation to first feeding would improve survival and performance of triploids compared to the diploid standard of 8 °C or any temperature alterations throughout embryogenesis. Triploids were more sensitive to post-ovulatory ageing as shown with significantly higher mortality and larger size variation compared to their diploid siblings. Quality indicators suggested that ageing resulted in increased lipid peroxidation and decreased antioxidant activity in unfertilised eggs, suggesting fertilising eggs within five days post-ovulation is beneficial for triploid culture. Nutritional programming was successfully demonstrated in Salmo salar of both ploidy. A nutritional intervention at the point of first feeding resulted in better acceptance and utilisation of vegetable-rich diets in later life. Ploidy generally responded the same, however triploids showed a higher variation in nutrient retention and LC-PUFA biosynthesis, highlighting the need to understand further the difference between nutritional requirements. Fundamentally, the impact of the second set of maternal chromosomes present in triploids is not understood. A panel of expressed microsatellite loci was identified and exploited to assess allele expression and results confirmed codominant expression of these genes in diploid fish. There was clear evidence that all three alleles present in triploids were expressed at both the offspring whole animal level and in blood samples, however poor amplification of RNA from single cells prevented further understanding. Collectively, these studies highlight differences in early life culture requirements of diploid and triploid Salmo salar.