Megabenthos and benthopelagic fishes on Southeast Atlantic seamounts

Abstract

January 2015. The distance between solid vertical lines represents 1 nautical mile (1 852 m). The summit of Erica has a minimum depth of ~880 m

Hydroids (Cnidaria, Hydrozoa) from the Vema and Valdivia seamounts (SE Atlantic)

“…Although this strong difference between hydroid communities is biased by the low number of samples examined, the environmental conditions clearly contribute to differentiate both seamount communities. The Vema Seamount, despite its isolated location in the middle of a deep abyssal plain at ca 450 nautical miles from the West African coast (Simpson & Heydorn 1965;Berrisford 1969;Bergstad et al 2019a), its summit reaches the euphotic zone, with a depth oscillating from 100 to 21.5 m at its shallowest peak (Bergstad et al 2019a(Bergstad et al , 2019b, and its benthic community is characterized by the abundance of coralline algae and prominent kelp forests (Simpson & Heydorn 1965;Berrisford 1969;Bergstad et al 2019b) (Fig. 9), with recorded temperatures of 16-18°C and a salinity of 35.6 psu at the summit of the seamount (Bergstad et al 2019b) (Fig.…”

“…The sampling program included, at each seamount, multibeam echosounder mapping, hydrographic surveys with a CTD profiler, visual observations of benthic megafauna using a 'CAMPOD' towed video rig, and biological sampling activities using bottom and midwater trawls for fish and other megafauna, and a van Veen grab for benthic invertebrates in soft bottoms. A more detailed description of sampling methodology can be found in Bergstad et al (2019aBergstad et al ( , 2019b. Hydroid samples were obtained from 11 stations located at Vema and Valdivia seamounts during trawl and grab operations.…”

“…They also attract top-predators such as sharks, pelagic fish, marine mammals and seabirds (Roberts 2018 and references therein). In addition, despite the fact that seamount biodiversity still remains unknown or poorly understood (Rowden et al 2010;Clark et al 2012), it is well documented that many seamounts are inhabited by vulnerable marine ecosystems (VMEs) that can easily be impacted by human activities (Bergstad et al 2019b).…”

“…In this way, and supported by the FAO (Food and Agriculture Organisation of the United Nations) and SEAFO (South East Atlantic Fisheries Organisation), a 29-day research cruise on board R/V Dr Fridtjof Nansen was conducted in January-February 2015, which aimed at mapping and analysing the occurrence and abundance of benthopelagic fish and sessile epibenthos on selected Southeast Atlantic seamounts. This region harbours hundreds of nearly unstudied seamounts with little available data, which is mainly focused on fisheries resources but lacks information on benthic communities (Bergstad et al 2019b). The only exceptions are the Vema Seamount, where detailed benthic research was conducted in 1964 (Simpson & Heydorn 1965;Mallory 1966;Berrisford 1969), and the Walvis ridge area, where several Spanish fisheries surveys were also conducted, including the study of some benthic taxa (Macpherson 1984;Alvà & Vadon 1989;Gili et al 1989;Zibrowius & Gili 1990;López Abellán & Holtzhausen 2011).…”

“…In this paper, we provide new information on the Southeast Atlantic hydroid fauna, based on the study of samples collected from the Vema and Valdivia seamounts during the cruise of the R/V Dr Fridtjof Nansen, carried out in 2015 in the SEAFO Convention Area. Data on bathymetry, substrate and fishing areas (Bergstad et al 2019a) and megabenthos and benthopelagic fish (Bergstad et al 2019b) obtained in the same cruise are already available.…”