title: Stable-isotope analysis of a deep-sea benthic-fish assemblage: evidence of an enriched benthic food web.
abstract: In this study, fishes and invertebrates collected from the continental slope (1000 m) of the eastern North Pacific Ocean were analysed using stable-isotope analysis (SIA). Resulting trophic positions (T(P) ) were compared to known diets and habitats from the literature. Dual isotope plots indicated that most species groups (invertebrates and fishes) sorted as expected along the carbon and nitrogen axes, with less intraspecific variability than interspecific variability. Results also indicated an isotopically distinct benthic and pelagic food web, as the benthic food web was more enriched in both nitrogen and carbon isotopes. Trophic positions from SIA supported this finding, resulting in the assignment of fishes to different trophic positions from those expected based on published dietary information. These differences can be explained largely by the habitat of the prey and the percentage of the diet that was scavenged. A mixing model estimated dietary contributions of prey similar to those of the known diet of Bathyraja trachura from stomach-content analysis (SCA). Linear regressions indicated that trophic positions calculated from SIA and SCA, when plotted against B. trachura total length for 32 individuals, exhibited similar variation and patterns. Only the T(P)  from SCA yielded significant results (stomach content: P < 0·05, stable isotope: P > 0·05).
authors.affiliation: Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA. boyle.mariah@gmail.com
authors.forename: M D
authors.initials: MD
authors.lastname: Boyle
authors.forename: D A
authors.initials: DA
authors.lastname: Ebert
authors.forename: G M
authors.initials: GM
authors.lastname: Cailliet
mesh_terms: D000818:Animals; D058448:Biota; D002247:Carbon Isotopes / Q000032:analysis; D004032:Diet; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D020387:Food Chain; D005766:Gastrointestinal Contents; D007448:Invertebrates / Q000502:physiology*; D016014:Linear Models; D008954:Models, Biological; D009587:Nitrogen Isotopes / Q000032:analysis; D010140:Pacific Ocean; D012860:Skates, Fish / Q000502:physiology*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes