Lipid composition and diet inferences in abyssal macrourids of the eastern North Pacific

The lipid compositions of 2 abyssal macrourids, Coryphaenoides armatus and C. yaquinae, from the eastern North Pacific were examined and used to infer diet. The resulting fatty acid (FA) profiles are the first published for C. yaquinae and among the first for abyssal fishes, They indicated a greater proportion of polyunsaturated FAs and lower monounsaturated FAs than shallower living congeners, suggestive of homeoviscous adaptations to great pressure. Cholesterol was the predominant sterol, which is frequently the case for exclusively carnivorous species. Comparisons of macrourid FA profiles were made to those of benthic prey and epipelagic carrion sources, including the Humboldt squid Dosidicus gigas captured in surface waters of the abyssal study site. The FA profiles of macrourid muscle were very similar to those of squid mantle muscle. The FA profiles of macrourid liver and swim-bladder were similar to benthic crustaceans, whole squid, squid digestive gland and the epipelagic fish Trachurus symmetricus. For both tissues, the FA profiles of echinoderms were the most different. These comparisons suggest a strong link to carrion and benthic crustaceans and a weak one to echinoderms, the dominant megafauna at the study site and in most of the abyssal ocean. These results support previous stomach content and stable isotope analyses, reinforcing the hypothesis that there are closer food web ties between abyssal fishes and epipelagic nekton than to many abyssal benthic groups.