Abstract
Abstract The influence of oceanographic variables on assemblages of meso- and bathypelagic fish was investigated along a Northeastern Atlantic Ocean transect (Cape Verde to the Bay of Biscay) during May 2019. Fish were collected using a mrozooplankton trawl during daylight hours at ten stations. Along the transect, 17 hydrographic stations were also performed with a CTD (Conductivity, Temperature, and Depth). A total of 130 fish taxa were identified. The dominant family was Gonostomatidae, with four species (Cyclothone braueri, Cyclothone microdon, Cyclothone pseudopallida, and Cyclothone pallida) being responsible of more than 78% of the total density. The most frequent species that appeared to be ubiquitous were C. braueri and C. pseudopallida, while Myctophidae was the most diverse family. Multivariate analyses revealed two clusters related with the latitudinal gradient. The fish community in the southern stations (25–37°N) was more diverse than in the northern stations (42–48°N). Temperature from 300 to 700 m depth explained 65% of variation in terms of density and 58% in terms of biomass, both statistically significant. The investigated variation in the deep-pelagic ecosystems on a large spatial scale gives essential information to ecosystem management approhes and marine spatial planning.
Highlights
The deep-pelagic ocean is the largest habitat by volume on Earth (Webb et al, 2010)
Fishes are an important component of the deep-sea ecosystems and, as intermediate trophic levels as well as top predators, a critical part of food webs (Drazen and Sutton, 2017)
The gonostomatid fishes C. braueri, C. microdon, C. pseudopallida, and C. pallida dominate our samples despite midwater fish trawls not being optimal for the sampling of these smaller sized individuals (Gartner et al, 1989; Olivar et al, 2017)
Summary
The deep-pelagic ocean (waters deeper than 200 m) is the largest habitat by volume on Earth (Webb et al, 2010). The deep-sea provides crucial ecosystem services, including the support of fisheries, the provision of energy, and mineral resources, as well as the regulation of the climate and nutrient cycling (Thurber et al, 2014). Because of this and its vulnerability to threats such as overfishing and climate change (Webb et al, 2010), it is necessary to increase our knowledge of the deep-pelagic ocean.
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