Effect of sexual maturation and triploidy on chemical composition and fatty acid content of energy stores in female rainbow trout, Oncorhynchus mykiss

Sexual maturation is an energy and nutrient demanding physiological process that alters growth efficiency and compromises muscle quality in many food fish species. Lipid mobilization supplies energy required for this process. To study the effect of sexual maturation on lipid mobilization in female rainbow trout on a high nutritional plane, fish growth, egg development, proximate composition, and fatty acid composition of muscle, liver, visceral fat, and gonads were determined for diploid (2N; fertile) and triploid (3N; sterile) females from July 2008 thru March 2009, when most 2N females ovulated. Previously, we reported there were minimal differences in most growth measurements between the 2N and 3N fish in this study, but there were changes in muscle proximate composition and visceral fat stores. Here, we report changes in proximate composition of liver, gonads, visceral adipose tissue, and fatty acid composition of these tissues and muscle during sexual maturation of 2N females with 3N females serving as the control. Similar and distinct patterns of change in fatty acids were observed between tissues of 2N and 3N fish, and among different tissues as the 2N fish were maturing. Highly unsaturated, long chain fatty acids appear to play an important role in gonadogenesis, either as a source of energy or for deposition in eggs to support offspring development and survival. Differences in growth and preferential mobilization of fatty acids are observed when fish are on a high nutritional plane compared to more typical, lower nutritional regimens.

► 2N and 3N female rainbow trout are used to study the effects of sexual maturation.
► We examine changes in growth, lipid mobilization, proximate and fatty acid composition.
► Visceral fat was mobilized first in 2N fish, but was not mobilized in 3N fish.
► Highly unsaturated fatty acids appear to play an important role in gonadogenesis.