A Gas Chromatograph/Mass Spectrometer is used to identify and quantify fatty acids (FAMEs)

In addition to determination of energy content, we often analyze in more detail to determine the types of building blocks that compose the lipids. This information gives us clues to the diet and quality of the habitat, and aids in the separation of unique stocks of fish if they have unique diet components at some locations. These clues are determined through separating the various classes of lipids, and then analyzing for the specific fatty acids that make up these building blocks. Fatty acids are long carbon chains (>10 carbons) that can vary in structure, length, and degree of saturation. Organisms synthesize fatty acids or obtain them in their diets and modify them to varying degrees. Consequently, the lipids within an organism comprise a complex array of fatty acids. Estimating the relative amounts of these fatty acids yields a “fingerprint”, which contains significant biological information.

In the Nutritional Ecology Laboratory, we examine variability of fatty acid signatures within marine forage species and factors contributing to the variation. Our work has shown that species can be readily identified on the basis of the fingerprints, however, significant within-species variation results from dietary and genetic differences among individuals. We can take advantage of these differences to infer trophic relationships and differentiate diet composition and quality among populations.

Stock Discrimination of Pacific Herring Using Heart Fatty Acids This figure shows how fatty acid analysis can be used to discriminate herring stocks. In a collaborative effort with the Alaska Department of Fish and Game, we used fatty acids to reliably assign herring to the appropriate spawning stocks. The figure shows how well the analysis separated herring from Sitka, Togiak, and spawning aggregations centered in Kodiak and Prince William Sound.

Use of Fatty Acids to Examine Shark Diets This cluster diagram maps the similarities in fatty acid composition between sleeper shark muscle and liver samples to archetypes of potential prey. The fatty acid composition of the shark tissues were most similar to those of blubbers removed from some shark stomachs. These blubbers, in turn, were most similar to zooplanktivorous fish, suggesting that sleeper sharks consume large amounts of blubber derived from baleen whales.

Contact
Ron Heintz
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries

Ted Stevens Marine Research Institute
17109 Pt Lena Loop Rd
Juneau AK 99801
(907) 789-6058
Ron.Heintz@noaa.gov