Vertical migratory behaviour of the euphausiid, Meganyctiphanes norvegica, and its dispersion in the Kattegat Channel

Abstract

The euphausiid Meganyctiphanes norvegica (Northern Krill) is predominantly an oceanic species common to the North Atlantic and adjacent seas. In the Kattegat the species concentrates in a series of depressions in the Kattegat Channel east of the island of Laesø which represent havens of marine conditions beneath the low salinity Baltic outflow.The vertical migratory behaviour of Meganyctiphanes results in it encountering considerable contrasts in physical conditions during its diurnal cycle. This behaviour and the resulting physical experience of the animals were investigated by means of a combination of net sampling and ADCP transects across the Alkor Deep (131 m) in summer (18-19/7/96) and winter (9-10/3/97).In both summer and winter the krill tended to concentrate within the basin during daytime and to disperse in the upper layers at night. The period of dispersion was longer in winter (17.00-05.00 h) than in summer (23.00-02.00 h). The complex layering of different wind-induced and tidal current systems acted to advect the krill away from the basin during their upward phase at night. ADCP measurements showed that in summer the krill would be advected SSW at an average rate of 3 cm s −1 , but that in winter they would be advected WSW at 3.2 cm s −1 . Calculations show that the krill would be capable of swimming against such currents without increasing their standard metabolism and that their distribution in the vicinity of the basin seems to be determined more by biotic than by abiotic factors.

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.…”

Modeling profitability for the smallest marine endotherms: auklets foraging within pelagic prey patches

“…It is believed that vertically migrating zooplankton often disperse horizontally as they become more vertically compacted near the surface (Smith et al 1989, Demer & Hewitt 1995, Tarling et al 1998. The extent to which this behavior results in less distinct patches with lower density near the surface, with increased costs of searching to locate high enough prey concentrations, is unknown.…”

Laboratory-Based Observations of Behaviour in Northern Krill (Meganyctiphanes norvegica Sars)

“…There have been many in situ studies of swarm behaviour of M. norvegica that have revealed something of their spatial and temporal occurrence (Aitken, 1960;Nicol, 1986;Tarling et al, 1998Tarling et al, , 1999. Aspects that have been of interest to behavioural physiologists looking at the level of the individual have included the mechanisms that may promote swarm formation and maintenance and the possibility of advantages to individuals in terms of reduced costs of swimming (Wiese & Ebina, 1995;Swadling et al, 2005).…”