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Marine Ecology Progress Series

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MEPS 441:241-255 (2011)  -  DOI:

Long-term acoustical observations of the mesopelagic fish Maurolicus muelleri reveal novel and varied vertical migration patterns

Arved Staby1,*, Anders Røstad2,3, Stein Kaartvedt2,3

1University of Bergen, Department of Biology, PO Box 7803, 5020 Bergen, Norway
2University of Oslo, Department of Biology, PO Box 1066 Blindern, 0316 Oslo, Norway
3King Abdullah University of Science and Technology, Saudi Arabia

ABSTRACT: We studied the temporal dynamics in the vertical distribution of Maurolicus muelleri scattering layers (SL) by examining continuous acoustic recordings over a 15 mo period in Masfjorden, Norway, complemented by intermittent sampling campaigns. The data revealed known patterns as normal diel vertical migration (DVM), midnight sinking between dusk and dawn, and periods without migrations, as well as novel behaviours consisting of early morning ascents, reverse diel vertical migrations, and interrupted ascents in the evening. During the first autumn of the study, adult fish modified their normal DVM behaviour by suspending their migration in the evening, yet ascending toward the surface in the later part of the night to reach upper layers during dawn. This behaviour was not observed during the second autumn of the study. By mid- to end of November (1st autumn), adult fish had suspended the nocturnal ascent entirely, and in the subsequent period until the end of January, a fraction of the population rather performed limited reverse migrations, slightly shifting their vertical distribution upwards during the first part of the day. From January to March 2008, fish interrupted their evening ascent at apparently random intervals and returned to deeper waters, instead of completing a full ascent to the surface. Our study underlines the value of long-term recordings, with the results suggesting that M. muelleri has the capability of changing its behaviour in response to ontogeny and internal state (satiation and hunger) as well as to external stimuli.

KEY WORDS: Diel vertical migration · DVM · Scattering layers · Maurolicus muelleri · Ontogeny · Stationary hydroacoustics

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Cite this article as: Staby A, Røstad A, Kaartvedt S (2011) Long-term acoustical observations of the mesopelagic fish Maurolicus muelleri reveal novel and varied vertical migration patterns. Mar Ecol Prog Ser 441:241-255.

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