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Marine Ecology Progress Series

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MEPS 521:189-200 (2015)  -  DOI:

Seasonal patterns in the nocturnal distribution and behavior of the mesopelagic fish Maurolicus muelleri at high latitudes

Perdana K. Prihartato1, Dag L. Aksnes2, Stein Kaartvedt1,3,*

1King Abdullah University of Science and Technology, Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia
2Hjort Centre for Marine Ecosystem Dynamics, Department of Biology, University of Bergen, Norway
3University of Oslo, Department of Biosciences, PO Box 1066 Blindern, 0316 Oslo, Norway
*Corresponding author:

ABSTRACT: Acoustic scattering layers (SL) ascribed to pearlside Maurolicus muelleri were studied in Masfjorden, Norway, using upward-looking echo sounders cabled to shore for continuous long-term measurements. The acoustic studies were accompanied by continuous measurements of surface light and supplemented with intermittent field campaigns. From autumn to spring, young M. muelleri formed an SL in the upper ~75 to 150 m in the daytime, characterized by migration to near-surface water near dusk, subsequent ‘midnight sinking’, followed by a dawn ascent before a return to the daytime habitat. Light levels were ~1 order of magnitude lower during the dawn ascent than for ascent in the afternoon, with the latter terminating before fish reached upper layers on ~1/3 of the nights from late November to mid-April. Adults showed less tendency of migration during autumn and winter, until the SLs of young and adults merged in late spring, and thereafter displayed coherent migration behavior. The midnight sinking became progressively deeper from autumn to winter but was strongly reduced from mid-May when the darkest nocturnal light intensity (PAR) at the surface was above 10-3 µmol m-2 s-1. The pearlside took on schooling in upper waters during the even lighter nights in early June, with minimum light of ~5 × 10-3 to 10-1 µmol m-2 s-1 at the surface. Nocturnal schooling ceased in early July, and midnight sinking reappeared in mid-August. We suggest that the strong variation in nocturnal light intensity at high latitudes provides changing trade-offs between visual foraging and avoiding predators and hence varying time budgets for feeding in the upper, productive layers.

KEY WORDS: Behavior · Diel vertical migration · Light levels · Mesopelagic · Acoustics

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Cite this article as: Prihartato PK, Aksnes DL, Kaartvedt S (2015) Seasonal patterns in the nocturnal distribution and behavior of the mesopelagic fish Maurolicus muelleri at high latitudes. Mar Ecol Prog Ser 521:189-200.

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