Fisheries aspects of seamounts and Taylor columns

Abstract

Three hypotheses to explain the high biological productivity observed over the southern Emperor-northern Hawaiian Ridge seamounts are suggested: larval retention to hydrodynamic trapping in a Taylor column, nutrient enrichment by topographically-induced upwelling , and attraction of organisms to stationary physical substrates. Quasi-geostrophic wave-topography interactions are considered, with particular regard to Taylor column dynamics. Data from three hydrographic surveys over Southeast Hancock Seamount conducted during summer 1984 and winter 1985 are examined for evidence supporting these hypotheses. The two summer surveys show features consistent with a two-layer systems having bottom-intensified anticyclonic flow around the seamount, in agreement with stratified Taylor column theory. The winter survey indicates more homogeneous anticyclonic flow around the seamount, suggesting the existence of a barotropic Taylor column. Possibly intense internal wave motion and upwelling are suggested by strong, localized vertical southern deflections in across-seamount sections taken during the summer surveys. These deflections are reminiscent of wave-topography interactions is atmosphere flow over terrestrial mountains. The second summer survey showed possible upwelling I the lee of the topographically-forced divergence.