Abstract
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 190:253-262 (1999) - doi:10.3354/meps190253 Vertical migration behaviour in the northern krill Meganyctiphanes norvegica is influenced by moult and reproductive processes G. A. Tarling1,*, J. Cuzin-Roudy2, F. Buchholz3 1Scottish Association for Marine Science, PO Box 3, Oban, Argyll PA34 4AD, Scotland, UK 2Observatoire Océanologique, UPMC CNRS INSU LOBEPM, Océanographie biochimique et Ecologie, BP 28, 06230, Villefranche-sur-Mer, France 3Biologische Anstalt Helgoland, Stiftung AWI, Meeresstation, Postfach 180, 27483 Helgoland, Germany *E-mail: gant@dml.ac.uk ABSTRACT: A population of the northern krill Meganyctiphanes norvegica was sampled between 24 July and 3 August 1998 in the Alkor Deep, Kattegat, in order to investigate the influence of sexual and developmental factors on the vertical distribution of adult krill. Depth-discrete samples of krill were taken with a 1 m2 MOCNESS net at the cardinal times of day (midnight, midday, sunrise and sunset). Specimens were immediately measured and categorised for moulting and spawning status. Further samples were preserved for detailed analysis in the home laboratory. Results showed that the population concentrated in the deep (80 to 100 m) during day-time but segregated vertically during night-time. Moulting occurred in the deep during night-time, away from the main part of the non-moulting population, which was located between 80 and 50 m. Spawning females were most evident in the uppermost depth interval (30 to 5 m). Moulting at night in the deepest layers may be viewed as a mechanism to avoid cannibalism whilst in a vulnerable condition. Spawning in the warm upper layers accelerates reproductive processes and may also reduce the depth to which the eggs sink before hatching into nauplii. KEY WORDS: Northern krill · Euphausiids · Swarming · Diel vertical migration · Spawning · Moulting · Sexual behaviour Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 190. Publication date: December 14, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.
Highlights
Sars 1857 has a wide geographic range and is found in many areas of the North Atlantic and Mediterranean (Boucher & Thiriot 1972, Lindley 1982).Northern krill typically swarm (e.g.Simard et al 1986, Buchholz et al 1995, Tarling et al 1999) and are strong vertical migrators (Mauchline & Fisher 1969, Mauchline 1980), exhibiting a normal die1 vertical migration pattern of ascent into the upper layers at dusk and descent at dawn (See review by Longhurst 1976).The vertical distance travelled during these migrations varies between locations
Greene et al (1992),for instance, found that a population of M. norvegica in the Gulf of Maine which resided at depth (200 to 250 m) during day-time segregated at night into 2 groups; one which performed a synchronised migration to the surface (50 to 0 m) and another which remained in the deep
The possibility that female spawning 1s influential in this respect is indicated by Nicol (1984),who found surface swarms of M. norvegica in the Bay of Fundy that were dominated by females in pre- or post-spawning condition together with large numbers of krill eggs in the plankton
Summary
Greene et al (1992),for instance, found that a population of M. norvegica in the Gulf of Maine which resided at depth (200 to 250 m) during day-time segregated at night into 2 groups; one which performed a synchronised migration to the surface (50 to 0 m) and another which remained in the deep. Kaartvedt et al 1996, Onsrud & Kaartvedt 1998) These approaches are satisfactory in dealing with the basic forces that induce krill to migrate vertically, such studies have not directly addressed the question of why night-time segregation occurs. The fact that moult and reproductive cycles are interlinked in female krill (Cuzin-Roudy & Buchholz 1999) suggests that more than 1 adult developmental process may influence vertical migration behavio'ur
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