title: Extensive geographic and ontogenetic variation characterizes the trophic ecology of a temperate reef fish on southern California (USA) rocky reefs.
abstract: Interactions between predator and prey act to shape the structure of ecological communities, and these interactions can differ across space. California sheepheadSemicossyphus pulcherare common predators of benthic invertebrates in kelp beds and rocky reefs in southern California, USA. Through gut content and stable isotope (δ13C and †15N) analyses, we investigated geographic and ontogenetic variation in trophic ecology across 9 populations located at island and mainland sites throughout southern California. We found extensive geographic variation in California sheephead diet composition over small spatial scales. Populations differed in the proportion of sessile filter/suspension feeders or mobile invertebrates in the diet. Spatial variation in diet was highly correlated with other life history and demographic traits (e.g. growth, survivorship, reproductive condition, and energy storage), in addition to proxies of prey availability from community surveys. Multivariate descriptions of the diet from gut contents roughly agreed with the spatial groupings of sites based on stable isotope analysis of both California sheephead and their prey. Ontogenetic changes in diet occurred consistently across populations, despite spatial differences in size structure. As California sheephead increase in size, diets shift from small filter feeders, like bivalves, to larger mobile invertebrates, such as sea urchins. Our results indicate that locations with large California sheephead present, such as many marine reserves, may experience increased predation pressure on sea urchins, which could ultimately affect kelp persistence.
authors.affiliation: Marine Science Institute, University of California Santa Barbara, California 93106-6150, USA ; Moss Landing Marine Laboratories, 8272 Moss Landing Rd, Moss Landing, California 95039, USA.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Hamilton
authors.affiliation: Marine Science Institute, University of California Santa Barbara, California 93106-6150, USA.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Caselle
authors.affiliation: Marine Science Institute, University of California Santa Barbara, California 93106-6150, USA.
authors.forename: Coulson A
authors.initials: CA
authors.lastname: Lantz
authors.affiliation: Marine Science Institute, University of California Santa Barbara, California 93106-6150, USA.
authors.forename: Tiana L
authors.initials: TL
authors.lastname: Egloff
authors.affiliation: Marine Science Institute, University of California Santa Barbara, California 93106-6150, USA.
authors.forename: Emi
authors.initials: E
authors.lastname: Kondo
authors.affiliation: Department of Zoology and Physiology, University of Wyoming, 1000 E. University Ave, Dept 3166, Laramie, Wyoming 82071, USA.
authors.forename: Seth D
authors.initials: SD
authors.lastname: Newsome
authors.affiliation: Deptartment of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, California 90840, USA.
authors.forename: Kerri
authors.initials: K
authors.lastname: Loke-Smith
authors.affiliation: Department of Biology, Moore Laboratory of Zoology, Occidental College, 1600 Campus Rd, Los Angeles, California 90041, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Pondella
authors.affiliation: Deptartment of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, California 90840, USA.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Young
authors.affiliation: Deptartment of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, California 90840, USA.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Lowe
keywords: California sheephead; Channel Islands; Demographic consequences; Feeding habit; Gut contents; Semicossyphus pulcher; Spatial variability; Stable isotopes