Growth efficiencies of essential fatty acids vary with dietary concentration in Atlantic Pollock (Pollachius virens)

Abstract

The essential fatty acids (EFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are required for the maintenance of good health in humans. In the marine environment, they are primarily synthesized by phytoplankton and their production is predicted to decrease with warming seawater temperatures. With reduced production, it becomes critical to understand the efficiency with which these EFA are transferred through trophic systems. To do this, captive Atlantic pollock ( Pollachius virens ) were fed one of two test diets for 83 days; both contained 11% total lipids, with one having half the absolute concentration of both EPA and DHA. Fish were hand-fed to satiation so a mass balance approach, monitoring intake and accumulation of EFA and energy, could be used to determine the FA-specific net growth efficiency (NGE). At the conclusion of the feeding study, NGE for EPA and DHA were determined at 56 and 52%, respectively, in fish fed diets that were rich in these EFA. However, in fish that received reduced dietary proportions of EPA and DHA, lower NGE, at 36 and 25%, respectively, were found, indicating that a limited ability to retain essential nutrients may exist when dietary supply is reduced. NGE for EFA in both diets, relative to energy, were 1.4–2 fold higher, offering a starting point for the development of trophic models evaluating transfer of these essential nutrients, rather than energy.