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

Abstract

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 swimbladder 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. The abyssal grenadier Coryphaenoides armatus feeds predominantly on crustaceans and carrion, and not on echinoderms, which are the most abundant benthic megafauna.

Characterization of forage fish and invertebrates in the Northwestern Hawaiian Islands using fatty acid signatures: species and ecological groups

“…FA trophic markers have long been recognized as efficient tools in studies of marine food webs (Sargent et al 1989, Budge et al 2002, 2006, Dalsgaard et al 2003. Recent studies have demonstrated that FAs can be successfully used to elucidate feeding ecology and trophic relationships of marine fish (Drazen et al 2009, Stowasser et al 2009) and invertebrates (Silina & Zhukova 2009, Spilmont et al 2009). However, northern/temperate and abyssal marine ecosystems have been the focus of most research efforts, and FA data regarding trophic interactions in tropical marine ecosystems are scarce (reviewed by Dalsgaard et al 2003).…”

Fatty acids as dietary tracers in benthic food webs

“…Studying the diet of deep sea species using more direct methods is problematic because the pressure changes experienced as animals are brought to the surface frequently causes regurgitation or stomach eversion, precluding analysis of stomach contents (e.g. sea stars, Howell et al 2003; macrourid fishes, Drazen et al 2009). Relative abundances of several diet-derived FAs varied among 7 species of deep sea holuthurians from the northeast Atlantic, suggesting a diversity of feeding modes or niches (Ginger et al 2000).…”

“…FAs are useful in habitats where direct observation would pose significant challenges, such as the deep sea (Howell et al 2003, Drazen et al 2009). FA tracers are also used to determine the fate of primary production, especially in habitats where the dominant primary producer is not directly consumed by the dominant herbivores (Meziane & Tsuchiya 2000, Kharlamenko et al 2001.…”

“…The scores of each sample on the first 2 to 3 principal components can be plotted to visualize relationships among samples. PCA has been used in benthic habitats to compare FA signatures of consumers to their potential food items (Guest et al 2008, Drazen et al 2009) and to classify consumers by feeding mode , Drazen et al 2008a, Richoux & Froneman 2008.…”

Does the physiology of chondrichthyan fishes constrain their distribution in the deep sea?

“…Unfortunately, the lipid accumulation strategy is unknown for deep-sea skates, which rival squaloids as the deepest chondrichthyans. In comparison, deep-sea teleosts such as macrourids store liver lipids as metabolic fuel rather than for buoyancy, so they have TAG-rich livers with negligible DAGE or squalene (Drazen, 2007;Drazen et al, 2009). …”