Journal Article

Vertical distribution of pre-settled sandeel (<i>Ammodytes marinus</i>) in the North Sea in relation to size and environmental variables

Henrik Jensen, Peter J Wright and Peter Munk

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 60, issue 6, pages 1342-1351
Published in print January 2003 | ISSN: 1054-3139
Published online January 2003 | e-ISSN: 1095-9289 | DOI: https://dx.doi.org/10.1016/S1054-3139(03)00150-4
Vertical distribution of pre-settled sandeel (Ammodytes marinus) in the North Sea in relation to size and environmental variables

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Vertical distribution patterns of larval and juvenile sandeels were investigated at four locations in the North Sea. Sandeels between 6 and 65 mm were found to depths of 80 m, with vertical distributions dependent on both length and environmental factors. At one location with a stratified water column, the highest densities were found during the day in midwater where food concentration was also highest. In areas without marked vertical hydrographic gradients, larvae were relatively more abundant in surface waters during the day. At all locations, larvae of all sizes were generally more homogeneously distributed in the water column during night than during day. The extent of vertical migration, as measured by the standard deviation of the mean depth, increased generally with length. Gear avoidance was evident for larvae ≥20 mm. Catch efficiency generally depended on both length class and surface light intensity. A simulated drift pattern of larvae, based on ADCP current measurements from two locations, predicts that the horizontal drift trajectory would only be affected slightly by the vertical positioning of the larvae in the water column during the time of sampling. The implication of vertical migrations for dispersal of larvae away from the spawning grounds is discussed.

Keywords: Ammodytes marinus; fish larvae; frontal zones; gear avoidance; hydrography; sandeel; vertical distribution

Journal Article.  4563 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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