Havforskningsinstituttet Tråling Postsmolt laks 2023 Sognefjorden

The dataset includes Institute of Marine Research data from trawl stations in Sognefjorden, Norway in 2023

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2023年挪威松恩峡湾（Sognefjorden）海洋研究所（Institute of Marine Research）的拖网采样站点实测数据。
海稚后期幼鲑（post-smolts）于晚春至初夏时节，在峡湾系统的外湾区域被采集：使用活鱼采样专用表层拖网，由长度15-25米的适配捕捞渔船拖曳作业。该拖网网深5米，最大网宽可达35米，具体尺寸取决于航行水速。
该拖网搭载了一套分选系统，可将海稚后期幼鲑等小型渔获与其他渔获分离，使幼鲑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穿过两组45°倾斜栅格完成：第一组栅格的栅条间距为10毫米，可将渔获提升至第二组栅条间距20毫米的栅格处完成最终分选；宽度超过20毫米的渔获将被输送至拖网囊网（cod end）部分。海稚后期幼鲑专用拖网的详细设计可参考Holst与McDonald（2000）发表于《Fisheries Research》第48卷第87-91页的研究成果。常规拖网作业航速为2-3节（相对于水速，STW），单次作业时长为2-4小时。
幼鲑被捕获后，需尽快在作业船舶上完成其体表鲑鱼虱的计数工作。使用剂量超标的200mg/ml苯佐卡因（Benzocaine）对幼鲑实施安乐死。将幼鲑浸没于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完成虱类计数。此项计数工作仅可由经过专门培训、可识别鲑鱼虱各发育阶段的人员开展。本次记录的虱类发育阶段包括：桡足幼体（copepodite）、chalimus 1期、chalimus 2期、预成虫期、雄性成虫期及雌性成虫期。同时记录幼鲑的体长（单位：毫米）与体质量（单位：克）。所有海稚后期幼鲑样本随后将被冷冻保存，用于后续分析。