A controlled feeding experiment investigating the effects of a dietary switch on muscle and liver fatty acid profiles in Port Jackson sharks Heterodontus portusjacksoni

Abstract

Fatty acid (FA) analysis is increasingly being used as a tool to investigate the diet of sharks and rays. Quantifying the diet of sharks using FA profiles, however, requires an understanding of the effects that fluctuating diet has on the biochemical pathways in different tissues, and of the time scales of FA integration. The effects of dietary changes on the muscle and liver FA profiles were investigated in a controlled feeding experiment with Port Jackson sharks (Heterodontus portusjacksoni) fed exclusively on squid then prawns for six weeks each. Multivariate analysis indicated that shark muscle and liver FA profiles were 9.8% and 7.7% dissimilar after dietary change. This suggests that dietary FAs are preferentially utilised by muscle after dietary change and that muscle FA profiles are a stronger indicator of dietary changes occurring within three weeks of sampling than the FA profiles of the liver. This should be carefully considered when determining the type of tissue and frequency of sampling needed to undertake chondrichthyan dietary studies based on FA profile analysis. Some FA biomarkers and their metabolic processes are also identified and described, but further work is required to enable quantitative assessment of a species diet. Data presented here gives justification towards more complex experiments to investigate metabolic and FA tissue incorporation rates.