The Atlantic spiny lumpsucker Eumicrotremus spinosus: life history traits and the seemingly unlikely interaction with the pelagic amphipod Themisto libellula

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.

Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web

Pinchuk, A. I., Coyle, K. O., Farley, E. V., and Renner, H. M. 2013. Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web. – ICES Journal of Marine Science, 70: 1244–1254. The eastern Bering Sea shelf experienced a sequence of warm years after a regime shift in the late 1970s. Following a series of unusually warm years in the early 2000s, the climate shifted again in 2007 to a series of extremely cold years that were marked by intense ice coverage and late ice retreat. Spatial and temporal variability in zooplankton communities during the recent cold period was investigated as part of the collaborative BEST-BSIERP program. An increasing presence of the Arctic hyperiid Themisto libellula, which had not been reported from the southeastern Bering Sea since the 1970s, was observed in the Middle Shelf Domain, indicating a developing structural shift in the zooplankton community in response to continuous cold conditions. Simultaneously, T. libellula became an increasingly dominant prey in the diets of zooplanktivorous fish and seabirds, demonstrating the important role for T. libellula in the pelagic food web. Our analysis suggests that T. libellula is capable of controlling copepod populations, thus it may become a potential contributor to top-down regulation of Calanus spp. in the eastern Bering Sea.