Demersal fish assemblages off the Seine and Sedlo seamounts (northeast Atlantic) |
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| Institution: | 1. Universität Hamburg, Institut für Hydrobiologie und Fischereiwissenschaft, Groβe Elbstraβe 133, D-22767 Hamburg, Germany;2. Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, L69 3GP, UK;1. School of Earth and Environment, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;2. Instituto de Ciências Sociais da Universidade de Lisboa, Av Prof Anibal Bettencourt, nr 9, 1600 Lisboa, Portugal;3. School of Animal Biology, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;1. Millennium Nucleus for Ecology and Sustainable Management of Oceanic Islands (ESMOI), Departamento de Biología Marina, Facultad de Ciencias del Mar, Universidad Católica del Norte, Coquimbo, Chile;2. Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Chile;3. Oceana Chile, Avenida Condell 520, Santiago, CP 7500875, Chile;4. National Geographic Society, Washington, DC, USA;1. Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada;2. Department of Molecular Biology and Biochemistry, Faculty of Science, Simon Fraser University, Burnaby, BC, Canada;3. Centre for Research in Infectious Diseases, National Institute of Respiratory Diseases, Mexico City, Mexico;4. British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada;5. Massachusetts General Hospital, Boston, MA, USA;6. Harvard Medical School, Cambridge, MA, USA;7. University of California San Francisco, San Francisco, CA, USA |
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| Abstract: | Seamounts are thought to support special biological communities, and often maintain high standing stocks of demersal and benthopelagic fishes. Seamount fish fauna have been described in several studies but few works have included species taken below 600 m. The demersal fish assemblages of the Seine and Sedlo seamounts (northeast Atlantic) from the summits to 2000 m depth were investigated based on longline survey catch data, conducted as part of the OASIS project. A total of 41 fish species from 24 families were caught at Seine near Madeira, and 30 species from 19 families were caught at Sedlo north of the Azores. Both fish faunas have high affinities with the neighbouring areas of the Azores, Madeira and with the eastern North Atlantic and the Mediterranean Sea. Overall abundances and mean body weights were slightly higher at Sedlo seamount, appearing in conformity with the latitudinal effect of increasing species abundance and productivity from south to north. The differential influence of the Mediterranean Water at each seamount may contribute to explain (a) the differences found in vertical distribution of common species, which tend to distribute deeper at Seine, and (b) the observed changes in the species composition and dominance in deeper waters. Multivariate analysis revealed a vertical structure that is approximately coincident with the expected zonation of water masses at each seamount. Physiological tolerance to the prevailing vertical hydrological conditions may explain the species distribution and the large-scale vertical assemblage structure found. However, further ecological factors like productivity patterns affecting the amount and quality of the available food appear to shape the abundance, diversity or dominance patterns of functional groups within those main assemblages. At Seine, the species Trachurus picturatus dominated the catches, mainly at the shallower edge of the plateau, appearing consistent with the sound-scattering layer interception hypothesis Isaacs, J.D., Schwartzlose, R.A., 1965. Migrant sound scatterers: interaction with the sea floor. Science 150, 1810–1813]. At both seamounts mesopelagic feeders (e.g., Beryx splendens) dominate the upper-slope assemblages (<800 m), while the mid-slope assemblages (800–1200/1300 m) and the lower-slope assemblages (>1300 m) were dominated by squaliform species (e.g., Centrophorus squamosus, Centroscymnus coelolepis, Etmopterus princeps) along with Mora moro or the Antimora rostrata. The lower abundance of C. squamosus observed at Seine may be a result of the fishing activities in the area, since the species is an important by-catch of the black-scabbard fish fishery in the Madeira archipelago. The slightly higher predominance of scavenger species at Seine in deeper assemblages may be the result of an ecological response favouring this functional group in lower productivity regimes. Especially relevant was the record of large reproductive aggregations of B. splendens and Epigonus telescopus found at the edge of the Sedlo plateau. |
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