The utility of commercial salmonid Oncorhynchus spp. traps in the U.S. Pacific Northwest was recently revisited for the first time in decades to enable selective harvesting of hatchery‐origin salmonids while reducing mortality of Endangered Species Act (ESA)‐listed salmonids. Modifications to historical gear designs resulted in dramatic improvements in salmonid bycatch survival rates relative to conventional commercial gears in the lower Columbia River. Expanding upon this work, an experimental commercial fish trap was further modified to largely eliminate net contact, air exposure, handling, and crowding of fish. Studies were conducted from May to November 2019 in the lower Columbia River to estimate survival of bycatch and evaluate potential benefits from the modified passive capture design. Analyzed through two separate survival estimation techniques, the modified trap demonstrated no detectable effect on salmon release survival and a significant improvement over the previous prototype design. Estimated through a paired release–recapture methodology, the relative survival effect of catch and release compared to controls over a 400‐km migration was 1.017 ( = 0.032) for adult Sockeye Salmon O. nerka. For adult Coho Salmon O. kisutch that were held captive for a 48‐h postrelease period, estimated survival (S) was 1.000 (lower 95% confidence limit: S ≥ 0.978). These results suggest that trap modifications can be made to significantly reduce bycatch mortality of ESA‐listed salmonids and provide increased opportunity for harvest of hatchery‐origin salmonids.

中文翻译：

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改良的商业鱼陷阱，以帮助消除鲑鱼兼捕死亡率

商业鲑鱼Oncorhynchus的实用程序spp。最近，几十年来首次对美国太平洋西北部的诱捕装置进行了重新检查，以实现选择性地收获孵化场的鲑鱼，同时降低《濒危物种法》（ESA）所列鲑鱼的死亡率。相对于哥伦比亚河下游的传统商用渔具，对历史渔具设计的修改导致鲑鱼副渔获物的存活率有了显着提高。在这项工作的基础上进行了扩展，对实验性的商业诱捕器进行了进一步修改，以在很大程度上消除鱼的净接触，空气暴露，处理和拥挤。研究于2019年5月至2019年11月在哥伦比亚河下游进行，以估计兼捕物的存活率并评估改良被动捕获设计的潜在好处。通过两种独立的生存估算技术进行了分析，改进的捕集阱对鲑鱼的释放存活没有可检测到的影响，并且比以前的原型设计有明显的改善。通过成对释放-重新捕获方法估算，与400 km迁移中的控制相比，捕获和释放的相对生存效应为1.017（= 0.032），用于成人红大马哈鱼O. nerka。对于成年银大马哈鱼O. kisutch被囚禁为48小时发布后时期，估计存活（小号）为1.000（95％的下置信限：小号 ≥0.978）。这些结果表明，可以进行捕集阱改造，以显着降低ESA所列鲑鱼的兼捕死亡率，并为孵化场鲑鱼的收获提供更多的机会。