Krill (Meganyctiphanes norvegica) swim faster at night

Thor Aleksander Klevjer, Stein Kaartvedt

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Krill are key members in marine food webs, and measurement of swimming speed is vital to assess their bioenergetic budgets, feeding, and encounters with predators. We document a consistent and marked diel signal in swimming speed of krill in their natural habitat that is not related to diel vertical migration. The results were obtained using a bottom-mounted, upward-looking echo sounder at 150-m depth in the Oslofjord, Norway, spanning 5 months from late autumn to spring at a temporal resolution of ~1–2 records s−1. Swimming speed was assessed using acoustic target tracking of individual krill. At the start of the registration period, both daytime and nocturnal average swimming speeds of Meganyctiphanes norvegica were ~ 3.5 cm s−1 (~ 1 body lengths ([bl] s−1) in waters with oxygen concentrations of ~ 15–20% O2 saturation. Following intrusion of more oxygenated water, nocturnal average swimming speeds increased to ~ 10 cm s−1 (~ 3 bl s−1), i.e., more than double that of daytime swimming speeds in the same period. We hypothesize that krill activity during the first period was limited by oxygen, and the enhanced swimming at night subsequent to the water renewal is due to increased feeding activity under lessened danger of predation in darkness.
Original languageEnglish (US)
Pages (from-to)765-774
Number of pages10
JournalLimnology and Oceanography
Volume56
Issue number3
DOIs
StatePublished - Mar 31 2011

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science

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