The feasibility of using sonar in Alaska's lower Kvichak River, a region with a 3.8 m tidal flux, to assess the abundance of adult Sockeye Salmon Oncorhynchus nerka was evaluated as a replacement for an in‐river gill‐net test fishery. Test fish indices are one tool that is used to manage commercial and subsistence fisheries in Bristol Bay. On this river, an observation tower project near the clear headwaters provides accurate abundance estimates for this species, but fishery managers require timelier estimates for in‐season daily management. The lower‐river test fish index is timelier, but it is less precise than tower estimates are. We had to determine whether to replace the test fish project with sonar based on how well each compared with tower estimates and an assessment of their cost and effort. Two dual‐frequency identification sonars (DIDSONs) were deployed along one bank of the lower river (one pointed toward shore and one away from shore) to assess salmon passage across all tidal stages in an attempt to produce an index with higher precision. Compared with the tower estimates, the test fish index showed a slightly stronger correlation in each of the three study years than the sonar index did, despite the stronger sampling power of the sonar. The test fish and sonar indices were strongly correlated. In the lower river, upriver salmon migration (85–98%) occurred primarily during ebb tides and downriver passage (97–100%) during flood tides, indicating that salmon do not use selective tidal stream transport to minimize their energy expenditures in this river. We were able to successfully use fixed‐location sonar in a tidal nearshore region to produce an index of fish abundance. Our recommendation was to continue the test fishing project rather than to replace it with sonar because of the similarity between their indices and the higher cost of the sonar project.

中文翻译：

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潮汐浑浊河中成年红鲑鱼评估：声纳法和测试捕鱼法的比较

在阿拉斯加的克维恰克河下游（潮汐流量为3.8 m的地区）使用声纳来评估成年红鲑鲑Oncorhynchus nerka的丰度被评估为内河网捕捞渔业的替代品。试验鱼指数是用于管理布里斯托尔湾商业和生计渔业的一种工具。在这条河上，清水源头附近的观测塔项目可为该物种提供准确的丰度估算，但渔业管理人员需要及时估算以进行季节性日常管理。下河试鱼指数较为及时，但其准确性不及塔楼估计值。我们必须根据每个声纳与塔估算值之间的比较程度以及对它们的成本和工作量的评估，来确定是否用声纳代替测试鱼项目。沿着下游的一条河岸部署了两个双频识别声纳（DIDSONs，DIDSONs）（一个指向海岸，另一个远离海岸），以评估鲑鱼在所有潮汐阶段的通过，以期得出更高精度的指标。与声纳指数相比，尽管声纳的采样能力更强，但在三个研究年度中，测试鱼指数的相关性均比声纳指数略强。被测鱼和声纳指数高度相关。在下游河中，上游鲑鱼迁移（85–98％）主要发生在退潮期间，而下游河道（97–100％）则发生在洪潮期间，这表明鲑鱼不使用选择性潮汐流运输来最大程度地减少其在河中的能量消耗。我们能够在潮汐近岸地区成功使用固定位置声纳产生鱼类丰度指数。我们的建议是继续进行测试捕鱼项目，而不是用声纳代替，因为它们的指标相似，并且声纳项目的成本较高。