Journal Article

Relationships between fish larvae and siphonophores in the water column: effect of wind-induced turbulence and thermocline depth

L. Sanvicente-Añorve, M. A. Alatorre, C. Flores-Coto and C. Alba

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 64, issue 5, pages 878-888
Published in print July 2007 | ISSN: 1054-3139
Published online May 2007 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1093/icesjms/fsm055
Relationships between fish larvae and siphonophores in the water column: effect of wind-induced turbulence and thermocline depth

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Sanvicente-Añorve, L., Alatorre, M. A., Flores-Coto, C., and Alba, C. 2007. Relationships between fish larvae and siphonophores in the water column: effect of wind-induced turbulence and thermocline depth. – ICES Journal of Marine Science, 64: 878–888.

The relationship between the abundance of fish larvae and siphonophores in relation to wind-induced turbulence and thickness of the mixed layer in the southern Gulf of Mexico were studied during two periods of different wind conditions: April (5.25 m s−1) and October (6.5 m s−1). The Spearman correlation between fish larvae and siphonophores revealed a random relationship in the 0–10 m layer during April and in the 0–20 m layer in October. This structure presumably persists while turbulent forces remain at sufficient strength. Positive patterns were observed deeper in the water column. Whereas thermocline position did not correspond with the depth separating random and positive relationships, low turbulence values did. Observations indicate that turbulent kinetic energy values above 4 × 10−4 J kg−1 might promote a random distribution between potential prey and predator zooplankton taxa. In surface waters, contact rates between siphonophores and fish larvae showed that turbulence enhances encounters 2.5 (1.2) times in April and 3.3 (1.3) times in October for prey velocities of 0.003 (0.011) m s−1. The positive relationship between fish larvae and siphonophores could be caused by a high degree of spatial overlap, enough food for both groups, and limited predation on larvae in the presence of alternative prey. Seasonal variability in the vertical structure of distribution patterns was attributed mainly to aggregative feeding behaviour of organisms and disruption of patches as a consequence of small-scale water turbulence.

Keywords: contact rates; Kolmogorov microscales; linear wave theory; mixed layer; predation; turbulent kinetic energy; vertical distribution; wind force

Journal Article.  5498 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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