Havforskningsinstituttet Tråling Postsmolt laks 2024 Boknafjord

The dataset includes Institute of Marine Research data from trawl stations in Boknafjord, 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.

本数据集涵盖2024年挪威博克纳峡湾（Boknafjord）各拖网站位的挪威海洋研究所（Institute of Marine Research）采集数据。
研究于晚春至初夏时节，在峡湾系统的外水域使用专用表层拖网开展活鱼采样，拖网由适配的15-25米长渔船拖曳。该拖网网身深度为5米，网口宽度可达35米，具体尺寸依水中航速而定。
该拖网搭载了分选系统，可将降海稚鱼（post-smolts）等小型渔获与其他渔获分离，使小型渔获在低紊流的水动力暂养舱内保持自由游动状态。分选过程依托水流经网道并穿过两组呈45度角的栅板完成：第一组栅板（栅条间距10毫米）将渔获提升至第二组栅板（栅条间距20毫米）处完成最终分选，宽度超过20毫米的渔获将被送入拖网囊网（cod end）。该降海稚鱼专用拖网的详细参数可参见Holst与McDonald（2000）发表于《渔业研究（Fisheries Research）》第48卷第87-91页的论文。典型拖网作业对水航速（STW）为2-3节，单次作业时长为2-4小时。
捕获的降海稚鱼将在船上第一时间开展鲑鱼虱（salmon lice）计数工作：首先使用过量的200mg/ml苯佐卡因（Benzocaine）对鱼体进行安乐死；计数时将鱼体置于5-10升的白色塑料盆中，使用亮度超过500流明的强光头灯辅助观察。计数工作仅可由经过鲑鱼虱各虫态鉴定专项培训的人员完成，本次记录的虫态类别包括：桡足幼体（copepodite）、第一期盾皮幼体（chalimus 1）、第二期盾皮幼体（chalimus 2）、预成虫期（pre-adult）、雄性成体及雌性成体。同时记录鱼体的体长（单位：毫米）与体质量（单位：克）。所有降海稚鱼样本将被冷冻保存，用于后续分析。