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Marine Ecology Progress Series

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MEPS 659:219-236 (2021)  -  DOI:

Biogeophysical influence of large-scale bathymetric habitat types on mesophotic and upper bathyal demersal fish assemblages: a Hawaiian case study

Astrid Brigitta Leitner1,2,*, Tobias Friedrich2, Christopher D. Kelley2, Seth Travis2, Dale Partridge3, Brian Powell2, Jeffrey C. Drazen2

1Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA
2Department of Oceanography, University of Hawai‘i, Mānoa, Honolulu, HI 96822, USA
3Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK
*Corresponding author:

ABSTRACT: Seamounts, pinnacles, and crests are abrupt seafloor features that modify physical processes and ecological patterns. Fishers often target these local bathymetric highs, which can have high catch-per-unit-effort. Increases in the abundance of target species has been qualitatively noted around these features and promontories, however, a quantitative evaluation of local highs as preferred habitat for fishes is still lacking. Here, we used an extensive database of fish abundances (N = 2381) from mesophotic and upper bathyal depths (40-300 m) gathered over 8 yr around the Main Hawaiian Islands to evaluate the effects of macro-scale habitat categorized by combining bathymetric position index (BPI) and slope. A numerical model simulating physical ocean processes was used to test the hypothesis that local highs, herein called crests, are distinct and preferred habitat for many species due to their modified flow conditions. We show that crests host a unique, diverse fish assemblage with double the abundance relative to other habitats. Therefore, fishes are concentrated at crests rather than being uniformly distributed along the island shelf at preferred depths. These habitats are characterized by enhanced current amplitudes and convergence zones. Direct correlations between fish abundance, convergence, and current amplitude strongly suggest that flow-enhanced food availability is likely the driver of habitat-related changes in fish assemblage. These results have important implications for conservation and management. We identify a simple and informative method to classify habitat, quantitatively link bathymetry-induced flow alterations to fish abundances, and provide information for refining definitions of essential fish habitat for species that are important commercial targets worldwide.

KEY WORDS: Baited camera · ROMS · Habitat association · Pinnacle · Mesophotic · Bathyal · Bathymetry

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Cite this article as: Leitner AB, Friedrich T, Kelley CD, Travis S, Partridge D, Powell B, Drazen JC (2021) Biogeophysical influence of large-scale bathymetric habitat types on mesophotic and upper bathyal demersal fish assemblages: a Hawaiian case study. Mar Ecol Prog Ser 659:219-236.

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