Article

Megabenthos and benthopelagic fishes on Southeast Atlantic seamounts

Published in: African Journal of Marine Science
Volume 41, issue 1, 2019 , pages: 29–50
DOI: 10.2989/1814232X.2019.1571439
Author(s): OA BergstadInstitute of Marine Research (IMR), Norway, M GilDepartamento de Ecología y Biología Animal, Edificio de Ciencias Experimentales, Spain, ÅS HøinesInstitute of Marine Research (IMR), Norway, R SarraldeInstituto Espanol de Oceanografia, Centro Oceanografico de Canarias, Spain, E MaletzkyMinistry of Fisheries and Marine Resources, Namibia, E MostardaFood and Agriculture Organization of the United Nations (FAO), Italy, L SinghBranch: Fisheries Management, Department of Agriculture, Forestry and Fisheries (DAFF), South Africa, MA AntónioSecretary of State of Affairs, Ministry of Agriculture, Rural Development and Fisheries, Angola, F RamilDepartamento de Ecología y Biología Animal, Edificio de Ciencias Experimentales, Spain, P ClerkinPacific Shark Research Center (PSRC), Moss Landing Marine Laboratories, United States, G CampanisSouth East Atlantic Fisheries Organisation (SEAFO) Secretariat, Namibia

Abstract

In a descriptive study of megafauna of several Southeast Atlantic seamounts, multiple video-transects on upper slopes and summits documented the occurrence of benthic invertebrate taxa, primarily corals, regarded as indicators of vulnerable marine ecosystems (VMEs) as defined in international guidelines. At Schmitt-Ott Seamount there was a pronounced dominance of gorgonian corals (seafans, Alcyonacea). In all other study areas the diversity was greater, and more scleractinians (stony corals, Scleractinia) were observed. Scleractinian corals were mainly dead, and much of the coral framework and rubble may have been ancient. In the Valdivia complex and on Ewing Seamount, which are open to fisheries, scleractinians seemed restricted to some slopes of knolls, and on Valdivia Bank and the subarea denoted Valdivia West the summit substrate was mostly bare rock. Pelagic armourhead Pseudopentaceros richardsoni and splendid alfonsino Beryx splendens (two targets of commercial fisheries in the area) were observed at a few sites, but did not appear to be abundant in the main former fishing areas of the Valdivia area. Orange roughy Hoplostethus atlanticus was common in video records around the summit at Ewing Seamount. The deep-sea red crab Chaceon erytheiae was abundant in the Valdivia area and at Ewing Seamount, and crabs were distributed across a more extensive depth range than the fishes. In areas with high densities of live coral, the video records suggested that the benthic communities were intact and not impacted by fishing. Evidence of past fishing activities included observations of lost pots and rope at Vema Seamount and in the Valdivia area.

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