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Marine Ecology Progress Series

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MEPS 429:227-244 (2011)  -  DOI:

Extensive geographic and ontogenetic variation characterizes the trophic ecology of a temperate reef fish on southern California (USA) rocky reefs

Scott L. Hamilton1,2,*, Jennifer E. Caselle1, Coulson A. Lantz1, Tiana L. Egloff1, Emi Kondo1, Seth D. Newsome3, Kerri Loke-Smith4, Daniel J. Pondella II5, Kelly A. Young4, Christopher G. Lowe

1Marine Science Institute, University of California Santa Barbara, California 93106-6150, USA
2Moss Landing Marine Laboratories, 8272 Moss Landing Rd, Moss Landing, California 95039, USA
3Department of Zoology and Physiology, University of Wyoming, 1000 E. University Ave, Dept 3166, Laramie, Wyoming 82071, USA
4Deptartment of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, California 90840, USA
5Department of Biology, Moore Laboratory of Zoology, Occidental College, 1600 Campus Rd, Los Angeles, California 90041, USA

ABSTRACT: Interactions between predator and prey act to shape the structure of ecological communities, and these interactions can differ across space. California sheephead Semicossyphus pulcher are common predators of benthic invertebrates in kelp beds and rocky reefs in southern California, USA. Through gut content and stable isotope (δ13C and δ15N) 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.

KEY WORDS: California sheephead · Channel Islands · Demographic consequences · Feeding habit · Gut contents · Semicossyphus pulcher · Spatial variability · Stable isotopes

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Cite this article as: Hamilton SL, Caselle JE, Lantz CA, Egloff TL and others (2011) Extensive geographic and ontogenetic variation characterizes the trophic ecology of a temperate reef fish on southern California (USA) rocky reefs. Mar Ecol Prog Ser 429:227-244.

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