Patterns in species richness,species density,and evenness in groundfish assemblages on the continental slope of the U.S. Pacific coast |
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Authors: | Nick Tolimieri |
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Institution: | (1) National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Blvd E, Seattle, WA 98112, USA |
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Abstract: | For many taxa, diversity, often measured as species richness, decreases with latitude. In this report patterns of diversity
(species richness, species diversity, and evenness) in groundfish assemblages were investigated in relation to depth (200–1200 m)
and latitude (33–47°N) on the continental slope of the U.S. Pacific coast. The data originated from the 1999–2002 upper continental
slope groundfish surveys conducted by the National Marine Fisheries Service. When the data were pooled across depths, species
density and evenness were found to decline with latitude. All three diversity measures declined with depth, with the lowest
overall diversity in the 600- to 900-m depth range where longspine thornyhead Sebastolobus altivelis constituted close to 70% of the catch. When latitudinal gradients were examined within four depth zones (200–300 m, 400–500 m,
600–900 m, and 1000–1200 m) more complex patterns emerged. At depth species richness and evenness were inversely correlated
with latitude as longspine thornyhead dominated catches to the north. However, in shallower areas of the slope, species richness
and evenness were positively correlated with latitude. Latitudinal patterns of diversity in the deeper zones and when pooled
across depths were positively correlated with temperature and broadly consistent with the Ambient Energy hypothesis discussed
by Willig et al. Annu Rev Ecol System 34:273–309 (2003)]. |
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Keywords: | Continental slope Depth Evenness Ground fish Latitudinal gradient Species density Species richness |
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