Characterization of the trophic niche for a Rockfish community in southeast Alaska

Rockfish are a group of marine fishes that exhibit significant ecological diversity as well as demand economic importance due to commercial and recreational fishing. We sampled Rockfish tissue from 2013 to 2018 in southeast Alaska off the southeast coast of Admiralty Island. Our objective was to characterize trophic niche and position of the Rockfish community using stable isotope analysis. We also wanted to observe any potential patterns regarding hypotheses of community composition. We found that the Rockfish community occupied a unique position in isospace in the context of other common species. Further, the isotopic niches of each Rockfish species were smaller than other common species. Between Rockfish communities, pelagic Rockfish occupied a significantly larger portion of isopace than demersal rockfish. The small niche size of Rockfish species compared to the large niche size of cooccurring common species suggests that the Rockfish community follows a niche differentiation model rather than a lottery model of community composition. The small niche size in isospace may be a function of competitive pressures among Rockfish species. Additionally, this pressure may be more prevalent in demersal Rockfish communities because they had generally smaller niche sizes than pelagic Rockfish.