Aggregations of Arctic cod (Boreogadus saida) in Allen Bay, on the southern coast of Cornwallis Island, Lancaster Sound were studied with fishery acoustics techniques in 1989 and 1990. Nonschooling fish were also examined in several Cornwallis and Devon Island bays. Although acoustic signal shading within the schools minimized abundance estimates (error may exceed 50%), measurements in 1989 indicated that two aggregations of adult Arctic cod together comprised at least 900 million individuals. Combined surface area of these two schools was 59 hectares, and total biomass was 30 715 tonnes (520 t•ha-1). Mean density in one school was 91 fish•m-3. In the other it was 307 fish•m-3 , each fish occupying a space equivalent to about one body length cubed. A smaller school studied in the same location a year later had a mean density of 72 fish•m-3. Mean length of net-captured fish from that school was 18.7 cm (TL), and mean weight was 44.5 g. School surface area was about 4.6 hectares, and it contained an estimated 2835 t of biomass (616 t•ha-1). Given that significant concentrations of biomass occurred in this small portion of the Lancaster Sound region, we concluded that, in theory, sufficient biomass was sequestered in fish schools within the region to support energy flows through the food web. Acoustic measurements indicated that fish at a school edge were larger (target strength [TS] =-44.7 dB, equivalent size = 19.3 cm) than nonschooling fish elsewhere (TS =-53.4 dB, equivalent size = 8.4 cm). Zooplankton abundance near a school was markedly reduced. Near Cornwallis Island, where water temperatures throughout the water column were >-1.3˚C, fish were scattered from surface to bottom. But near Devon Island, fish were common only in warmer surface waters (> 2.0˚C) above a marked thermocline at about 35 m, but not deeper, where water temperature was-1.5˚C.

The data provide important mechanistic information on the cause of hepatic injury in obese-HCV subjects including: (1) enhanced T helper-1 cytokine response patterns-to promote hepatocellular injury; (2) increased expression of the chemokines IP-10 and MCP-1 at both the mRNA and protein levels-to enhance inflammatory cell recruitment; (3) differing localisation of these chemokines within the liver of obese-HCV versus lean-HCV subjects-implying different inducing stimuli and; (4) increased CD3 expression in the liver of obese-HCV subjects-concordant with the increased expression of T cell chemoattractants.

SynopsisConcentrations of arctic cod were detected with a hydroacoustic system in Resolute Bay, NWT during 2 weeks in August of 1986. Fish biomass within the bay was about 30 t. The fish were feeding primarily on amphipods, which were abundant. When the daily location of the schools was examined in relation to the extent and position of drifting pack ice, a pattern emerged suggesting that the distribution of the fish was influenced by the amount and location of ice cover. If the bay was relatively ice-free, the density of schooling cod was high and the size of the schools, as 2-dimensional surface area, was generally small. When ice covered the bay, density within the schools was lower and they occupied more area. Arctic cod were most dispersed after the bay had been filled with pack ice for several days. It is postulated that this behaviour is a response to potential predation by seabirds and marine mammals.

Using acoustic telemetry techniques, the movements and habitat utilization of anadromous Arctic charr (Salvelinus alpinus) were determined when they entered the Freshwater Creek Estuary (Cambridge Bay, Northwest Territories, Canada) in the spring. The study was carried out during the transition from full ice cover to open water.Between 23 June and 1 July 1996, nine adult Arctic charr were tagged with external acoustic transmitters. These fish were tracked until 6 July using two radio-linked acoustic array systems and a portable manual receiver with a directional hydrophone. Two transmitters measured temperature and location, one measured depth and location and the remaining six, location only.All of the tagged charr remained in Cambridge Bay Estuary until the sea-ice had melted and the mouth of the bay was ice-free. Primarily, they remained in the warmer brackish surface layer which was ∼2 m thick and rarely moved into the colder underlying marine waters. As well, the tagged charr remained either near the shore or over offshore shoals, following the ice-edge as it melted down the estuary. Residence time in the estuary was greater than ten days for some fish. Therefore, in spite of evidence from controlled laboratory studies that have shown that Arctic charr are preadapted to the marine environment and are capable of migrating directly into seawater, this study shows that, in the wild, they prefer to remain in warmer brackish water until the sea-ice has melted and that the transition stage is longer than previously suggested.