Havforskningsinstituttet Tråling Postsmolt laks 2024 Hardangerfjord

The dataset includes Institute of Marine Research data from trawl stations in Hardangerfjord, Norway in 2024.

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.

本数据集包含2024年挪威哈当厄尔峡湾（Hardangerfjord）拖网站点采集的挪威海洋研究所（Institute of Marine Research）数据。研究于晚春和初夏在峡湾外湾区域采集降海稚鲑（post-smolt）：采用专用活鱼采样表层拖网，由适配的15-25米长渔船拖曳。该拖网深度为5米，宽度可达35米，具体数值取决于水下航行速度。该拖网搭载分选系统，可将降海稚鲑等小型渔获与其他渔获分离，使小型渔获在低湍流的水动力水族箱中保持自由游动状态。分选过程通过水流流经网道并经过两组45°斜置格栅完成：第一组格栅（栅条间距10毫米）将渔获提升至第二组格栅（栅条间距20毫米），在此完成最终分选；宽度超过20毫米的渔获将进入拖网囊网（cod end）。该专用拖网的详细参数详见Holst与McDonald（2000）发表于《Fisheries Research》第48卷第87-91页的研究成果。常规拖曳航速为2-3节（STW），单次作业时长为2-4小时。捕获降海稚鲑后，需尽快在作业船舶上完成其体表寄生虫计数。实验鱼使用过量浓度为200 mg/ml的苯佐卡因（Benzocaine）进行安乐死。计数时将鱼体置于容积5-10升的白色塑料盆中，使用亮度超过500流明的头灯辅助观察，且仅由经过专门培训、可识别鲑鱼虱各发育阶段的人员完成操作。本次记录的寄生虫发育阶段包括：桡足幼体（copepodite）、第一期附着幼体（chalimus 1）、第二期附着幼体（chalimus 2）、亚成体（pre-adult）、雄性成体与雌性成体。同时记录鱼体体长（单位：毫米）与体质量（单位：克）。所有降海稚鲑样品随后将被冷冻保存，以待后续分析。