MEPS - Vol. 452- Feature article

Pelagic and demersal fishes undertake vertical migrations in response to internal waves, as these cause changes in light penetration through the turbid surface layer of the sea. Illustration: Hege Vestheim

Kaartvedt S, Klevjer TA, Aksnes DL

 

Internal wave-mediated shading causes frequent vertical migrations in fishes

 

Internal waves are ubiquitous in the oceans. Kaartvedt and co-workers show that internal waves mediate underwater light conditions: at the trough of an internal wave, the turbid surface layer becomes deeper, integrated light extinction increases, and the waters at depth become darker; at the crest, the turbid layer is shallower and light penetration increases. Pelagic and demersal fishes ascend as it becomes darker and descend when it is lighter, and the time scale of these migrations corresponds to the periodicity of the wave. The authors hypothesize that these frequent migrations increase the number of prey encounters and the time available for safe visual foraging, thus improving fish growth and survival, and trophic transfer efficiency in the system.

 

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