Diel vertical migrations ofMeganyctiphanes norvegica in the Kattegat: Comparison of net catches and measurements with Acoustic Doppler Current Profilers

Abstract

Diel vertical migration of a stable and well-defined population of Nordic krill, Meganyctiphanes norvegica {Crustacea, Euphausiacea) was investigated during eight days in August 1989, in the L~s6-Deep, East of the Danish island L~is6. Net catches with a multi-net (MOCNESS) and measurements with a moored and a shipboard Acoustic Doppler Current Profiler (ADCP) were compared. Backscattered energy as a measure for biomass gave good correlations to the dry weight of M. norvegica and smaller zooplankton from net catches. Diel migratory patterns matched well, as determined, parallel with both methods. Migratory vertical velocity was determined with ADCP at 2-3 cm sec -I. The potential for the use of ADCPs for biological investigation is discussed. Vertical migration was dependent on environmental parameters. The krill did not cross a temperature barrier of 14~ although rich food sources were situated beyond it. Differences in salinity did not play a role. Currents were involved in plankton distribution. Light was an important Zeitgeber (synchronizer) and determined the density of the krill aggregations. Feeding behaviour did not interfere with the light-induced migratory pattern of Nordic krill at the L~is6-Deep.

Diurnal signals in vertical motions on the Hebridean Shelf

“…Enright and Honeggar (1977) showed the occurrence and timing of migration of the copepod Calanus helgolandicus was not sensitive to a reduction in light level resulting from overcast weather conditions. In contrast, Buchholz et al (1995) showed that M. norvegica were well dispersed with depth on overcast days and were concentrated into discrete bands on clear days. A similar conclusion was drawn by Roe (1983) following a study of euphausiids in the northeastern Atlantic.…”

“…M. norvegica has been observed, by means of an ADCP, to migrate from depths of 150 m to the surface at speeds of 0.02-0.03 m s-l (Buchholz et al 1995), while Frank and Widder (1997) report observing M. norvegica migrating at rates in excess of 0.1 m s-1. It has also been reported that both N. couchi (Williams and Fragopoulu 1985) and E. krohni (Roe et al 1984) have distinct migration cycles and are able to move vertically with speeds of 0.01-0.02 m s-1, although Williams and Lindley (1982) found no evidence of large-scale migration of T. longicaudata.…”

Food utilization of two pelagic crustaceans in the Greenland Sea: Meganyctiphanes norvegica (Euphausiacea) and Hymenodora glacialis (Decapoda, Caridea)

“…Mauchline 1980, Sameoto 1980, McClatchie 1985, Lass et al 2001. Although prey preference varies strongly with season and location (Lass et al 2001), the feeding mode of northern krill has been classified as opportunistic and non-selective (Mauchline 1980, Buchholz et al 1995, Lass et al 2001). However, Kaartvedt et al (2002) suggested that carnivorous feeding is performed selectively by visually hunting zooplankton, e.g.…”

Diel vertical migration and the haemocyanin of krill Meganyctiphanes norvegica

“…Nordic krill Meganyctiphanes norvegica (M. Sars) undergoes a pronounced DVM throughout its geographical range (Sameoto 1980, Simmard et al 1986, Buchholz et al 1995, Onsrud & Kaartvedt 1998, Tarling et al 1998, Liljebladh & Thomasson 2001, a behaviour widely thought to result from a trade-off between securing food (surface layers) and reducing predation (deeper layers) (Banse 1964, Lampert 1989, Tarling et al 2000, Alonzo & Mangel 2001. This may necessitate traversing pycnoclines resulting in individuals periodically residing in bodies of water that may differ dramatically in their temperature, salinity and O 2 properties (Mauchline & Fisher 1969, Simmard et al 1986, Onsrud & Kaardvedt 1998, Spicer et al 1999.…”