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Marine Ecology Progress Series

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MEPS 360:201-209 (2008)  -  DOI:

Behavior of individual mesopelagic fish in acoustic scattering layers of Norwegian fjords

Stein Kaartvedt1,*, Thomas Torgersen2,4, Thor A. Klevjer1, Anders Røstad1, Jennifer A. Devine3,5

1Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway
2Department of Biology, University of Bergen, 5020 Bergen, Norway
3Department of Biology, Memorial University, St. John’s, Newfoundland A1C 5S7, Canada
4Present address: Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway
5Present address: National Institute of Water and Atmospheric Research Ltd., Private Bag 14-901, Kilbirnie, Wellington, New Zealand

ABSTRACT: Mesopelagic acoustic scattering layers (SLs) in 2 fjords were studied from a stationary research vessel. Diel vertical movements of SLs were assessed by hull-mounted transducers, while in situ behavior of individuals constituting the SLs was resolved by a submerged echo sounder. The study focused on SLs made up of the lightfish Maurolicus muelleri and the lanternfish Benthosema glaciale. Individual fish migrated in a pronounced stepwise manner, alternating between vertical movements and stationary phases both during ascent and descent. Mean lengths of steps varied between 2.01 and 0.40 m, and mean duration of stationary phases between 69 and 36 s for fish in different SLs. Such travel-pause behavior concords with saltatory search, where fish scan the water for prey during the stationary phases, relocate and scan a new water parcel. Little activity was recorded among individuals in deep water, apart from infrequent, short shifts in vertical distribution. This study shows that stationary submerged echo sounders can provide detailed information on in situ behavior of mesopelagic fish.

KEY WORDS: Benthosema glaciale · Maurolicus muelleri · Diel vertical migration · Saltatory search · Acoustics · Fjords

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Cite this article as: Kaartvedt S, Torgersen T, Klevjer TA, Røstad A, Devine JA (2008) Behavior of individual mesopelagic fish in acoustic scattering layers of Norwegian fjords. Mar Ecol Prog Ser 360:201-209.

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