Are You What You Eat?

A promising new technique to determine dietary history and foraging ecology is being tested using captive Steller sea lions. The technique is based on the observation that fish contain many long chain fatty acids that are specific to individual prey items. When marine mammals eat fish, these fatty acids are incorporated into their blubber, leaving a unique signature that biochemists hope to use to determine the species of fish consumed. Unlike fecal remains (scats) which represent a meal consumed over the past 1-6 days, fatty acids may represent the diet over 1-6 months. Fatty acid signatures may also provide evidence of prey (such as crustaceans) potentially missed when diet is estimated solely from hard remains found in scats.

The first set of experiments being conducted by Consortium researchers is testing the ability of the fatty acid technique to quantitatively describe a diet of mixed composition, as well as to give information on how long these signatures last in the blubber. A small blubber biopsy and a sub-sample of the fish fed to each sea lion are presently being analyzed by Dr Sara Iverson of Dalhousie University. Fellow collaborators, Drs Tollit, Trites and Rosen will soon compare the results from the fatty acid signatures with the amounts of prey fed to each sea lion.

4 March 2002