Two species of Amphipoda (Hyperiidae), Themisto libellula (Mandt, 1822) and Themisto abyssorum (Boeck, 1870), were collected with the use of a WP-2 net from the area between Nordkapp and Spitsbergen (73° to 78° N) in July of 1993,1996,1997 and 1998. Densities ranged from 6 to 992 ind. 100 m-3 (T. abyssorum) and from 8 to 448 ind. 100 m-3 (r. libellula) and respective total biomass of T. abyssorum from 65.6 to 81.2 mg d.w. 100 m-3 and T. libellula from 59.9 to 131.5 mg d.w. 100 m-3.
During a cruise to Svalbard in September 2012 a unique collection of the little known but widely distributed Atlantic spiny lumpsucker ( Eumicrotremus spinosus ) was made in the Hinlopen Strait. A total of 140 individuals (36–101mm total length) were collected using a bottom trawl. All individuals were sexed and 26 of these were also analysed for gonadosomatic index (GSI), hepatosomatic index (HSI) and stomach content. The sex ratio of the entire sample showed a strong bias towards females (75% of all examined specimens). The GSI ranged from 1.4 to 5.8% except for one female with a GSI of 20%. All females carried gonads in which eggs were clearly visible, independent of size, indicative of an early sexual maturation and an iteroparous life cycle of females. All examined specimens had almost an exclusively pelagic diet, with Themisto libellula constituting 100% of the stomach content in 80% of the examined fishes. The results are discussed in relation to diel vertical migration of Arctic zooplankton and deep migrating layers.