Abstract
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 179:113-121 (1999) - doi:10.3354/meps179113 Can predator avoidance explain varying overwintering depth of Calanus in different oceanic water masses? Trine Dale1,*, Espen Bagøien1, Webjørn Melle2, Stein Kaartvedt1 1Department of Biology, University of Oslo, PO Box 1064 Blindern, N-0316 Oslo, Norway 2Institute of Marine Research, PO Box 1870 Nordnes, N-5024 Bergen, Norway *E-mail: trine.dale@bio.uio.no ABSTRACT: Distributions of overwintering Calanus spp. in the upper 1000 m in the Norwegian and Greenland Seas were studied in relation to hydrography, invertebrate predators and acoustic scattering layers (38 kHz). C. finmarchicus was concentrated deepest in the Atlantic domain, inhabiting the Arctic Intermediate Water (AIW) below the Atlantic Water (AW). It was less deeply distributed in the Arctic domain, where AIW reached the surface. The temperature of the overwintering habitats was mainly between -0.5 and +0.5°C, irrespective of region and overwintering depth. The distributions of invertebrate predators such as chaetognaths and the carnivorous copepods Euchaeta spp. and Chiridius sp. provided no explanation for the varying vertical distributions of C. finmarchicus. A conspicuous coupling between the level of acoustic backscattering (38 kHz) and the type of water mass (i.e. AW or AIW) was found. High acoustic backscattering, which we ascribe to planktivorous mesopelagic fishes, was confined to the relatively warm AW. The colder AIW was almost devoid of backscattering. Thus C. finmarchicus appear to overwinter in waters with a low abundance of planktivorous fish in all parts of the ocean. Since temperature and predator distribution as revealed by acoustics were closely coupled, predator avoidance is an alternative explanation to metabolically motivated temperature preference in Calanus' choice of overwintering depth. KEY WORDS: Calanus · Overwintering · Acoustic scattering layers · Mesopelagic fish · Invertebrate predators · Temperature Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 179. Publication date: April 15, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.
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