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Abstract:
Marine CO2 system data (total alkalinity, and total dissolved inorganic carbon) and nutrients were collected from full water column on the IMR repeat section between Fugløya-Bjørnøya in the Barents Sea Opening onboard the RV Kristine Bonnevie on cruise number 2021606. This study is a contribution to the project Monitoring ocean acidification in Norwegian waters/Havforsuringsovervåking i norske farvann” funded by the Norwegian Environment Agency (Miljødirektoratet) project# 17078007.
Post-smolts were collected in the outer parts of the fjord systems in late spring and early summer with a specialized surface trawl for live fish sampling, towed behind a suitable fishing vessel (15-25 m). The trawl is 5 m deep and up to 35 m wide depending on speed through water.
The trawl is mounted to a system where smaller catch, such as post-smolts are separated from other catch, and remain free swimming in low turbulence in a hydrodynamic aquarium. The separation takes place when the current flow through a net tunnel and over two 45 degrees racks. The first rack (10 mm between bars) lifts the catch to the next (20 mm between bars) where the separation is done. Everything wider than 20 mm will continue to the cod end of the trawl. Details of the post-smolt trawl are described in Holst and McDonald (2000), Fisheries Research 48, pp 87-91. Typical trawling speed is 2-3 knots (STW) with a duration of 2-4 hours.
Lice counts on post-smolts were performed on the ship as soon as possible after they were captured. The fish were killed using an overdose of Benzocaine 200 mg/ml. Lice counts were performed with the fish submerged in a white plastic tub (5-10 l) using a strong headlamp (>500 lumen). The counts were only performed by personnel with special training in identification of all salmon lice stages. The following categories were recorded: copepodite, chalimus 1, chalimus 2, pre-adult, adult male and adult female. Fish length in mm and mass in gram were recorded. All post-smolts were then frozen for subsequent analysis.