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Evaluating the role of bycatch reduction device design and fish behavior on Pacific salmon (Oncorhynchus spp.) escapement rates from a pelagic trawl
Fisheries Research ( IF 2.4 ) Pub Date : 2020-12-21 , DOI: 10.1016/j.fishres.2020.105830
Noëlle Yochum , Michael Stone , Karsten Breddermann , Barry A. Berejikian , John R. Gauvin , David J. Irvine

Pacific salmon (Oncorhynchus spp.) bycatch is a significant driver in the management of walleye pollock (Gadus chalcogrammus) pelagic trawl fisheries in the North Pacific. Various bycatch reduction devices that permit salmon to escape from the trawl (‘excluders’) have been developed. High variability in escapement rates from the excluders underscores a lack of understanding regarding mechanisms that promote escapement. We developed an excluder that provided a 360˚ open area for escapement during towing, turns, and haulback. We used computational fluid dynamics simulations and flume tank testing to expedite development by producing quantitative flow and net mensuration data, which reasonably predicted performance at full scale under commercial conditions. During at-sea trials, salmon escapement rates were high (mean 0.58 ± 0.18); however, more comprehensive testing is needed among salmon species and over a breadth of fishing conditions. Video footage revealed that salmon disproportionately escaped by swimming forward from aft of the excluder during haulback and turns. This highlights the importance of providing an open path to the escapement area during these periods. Retention of any salmon despite the expansive, easily accessible open area reflects the important role played by perception of the open area and motivation of salmon to escape at that point in the fishing process.



中文翻译:

评估兼捕减少设备设计和鱼类行为对浮游拖网的太平洋鲑鱼(Oncorhynchus spp。)逃逸率的作用

太平洋鲑(Oncorhynchus spp。)兼捕是管理角膜白斑鳕(Gadus chalcogrammus)的重要驱动力)北太平洋中上层拖网渔业。已经开发出各种减少鲑鱼捕获的副渔获物(“排除物”)。排斥者的逃逸率差异很大,这说明缺乏对促进逃逸机制的理解。我们开发了一种排除器,可以在拖曳,转弯和回头时提供360˚的开放区域供逃生。我们使用计算流体动力学模拟和水槽测试通过产生定量的流量和净测量数据来加快开发速度,这些数据可以合理地预测商业条件下的满量程性能。在海上试验中,鲑鱼的逃逸率很高(平均值为0.58±0.18)。但是,需要对鲑鱼种类和整个捕鱼条件进行更全面的测试。录像显示,在回头和转弯时,鲑鱼从排泄物的船尾向前游动,从而大量逃脱。这突出了在这些时期提供通向逃生区的开放路径的重要性。尽管有广阔的,易于接近的开放区域,但任何鲑鱼的保留都反映出感知开放区域和鲑鱼在捕捞过程中当时逃逸的动机所起的重要作用。

更新日期:2020-12-22
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