Chum salmon escapement on Bonanza River in Norton Sound, Alaska

Bonanza River flows 40 rkm south from the Kigluaik Mountains and drains into Safety Sound approximately 39 km northeast of Nome, Alaska. Chum, pink, and coho salmon are the predominant species that return to the Bonanza River. A fixed-picket weir was installed approximately 11 rkm above the Bonanza Bridge on the Nome-Council Highway (GPS coordinates 64°32.964ʹN, 164°35.812ʹW). The Bonanza River weir enumerated chum salmon for three seasons from 2018 to 2020. Chum salmon escapements were 7,903 in 2018; 8,824 in 2019; and 2,471 in 2020. In 2018 and 2019, high water delayed installation of the weir and therefore the beginning of the run may have been missed. Additionally, in 2019 high water forced weir operations to stop before the proposed end date, so it is likely the end of the chum salmon run was missed. In 2020, the weir went in according to schedule and counted the beginning of the run, but personnel issues, exacerbated by COVID-19 protocols, resulted in early termination of the project, and likely caused missed counting at the end of the run. High water that hindered counting on Bonanza River in 2018 and 2019 also hindered counting operations on other Subdistrict 1 rivers, and as a result aspects of Objectives 1 and 2 could not be completed for all project years. Age, sex, and length data were collected from chum salmon passing through the weir in all three years. Minimum sample size requirements to evaluate Objective 3 were met in 2018 and 2020, but not in 2019. In 2018, chum salmon were predominantly 4 years old and in 2020 chum salmon were predominantly 5 years old. This project indicated that using existing methods, such as weirs and aerial surveys, to estimate Bonanza River’s contribution to chum salmon abundance in Subdistrict 1 provide a reasonable approximation of chum salmon escapement in the absence of an enumeration project on Bonanza River.

博南扎河（Bonanza River）自基格卢艾克山脉（Kigluaik Mountains）向南流淌40河程公里（rkm），最终注入阿拉斯加州诺姆市（Nome）东北约39公里处的安全湾（Safety Sound）。洄游至该河的鲑鱼优势种为大麻哈鱼（chum salmon）、粉鲑（pink salmon）与银鲑（coho salmon）。研究人员在诺姆-康瑟尔公路（Nome-Council Highway）上的博南扎桥上游约11河程公里（rkm）处安装了固定桩式拦鱼堰（fixed-picket weir），其GPS坐标为64°32.964′N，164°35.812′W。该拦鱼堰于2018至2020年的三个渔季内对大麻哈鱼进行了计数统计。2018年、2019年与2020年的大麻哈鱼洄游个体总量分别为7903尾、8824尾与2471尾。2018年与2019年，高水位导致拦鱼堰安装工期延误，因此可能遗漏了该渔季初期的洄游种群计数。此外，2019年高水位迫使拦鱼堰作业在预定结束日期前终止，大概率遗漏了该渔季末期的大麻哈鱼洄游计数。2020年，拦鱼堰按计划安装并完成了初期洄游种群计数，但受新冠疫情防控协议影响的人员调度问题导致项目提前终止，大概率遗漏了该渔季末期的计数工作。2018年与2019年阻碍博南扎河计数作业的高水位，同样对第一分区（Subdistrict 1）内其他河流的计数工作造成了干扰，因此项目所有执行年度内，目标1与目标2的部分内容均未能完成。三个渔季期间，研究人员均从通过拦鱼堰的大麻哈鱼个体上采集了年龄、性别与体长数据。2018年与2020年的采样样本量均达到了评估目标3所需的最低样本量标准，但2019年未达标。2018年的大麻哈鱼种群以4龄个体为主，2020年则以5龄个体为主。本研究结果表明，在未部署博南扎河专属计数项目的情况下，采用拦鱼堰与航空调查等现有方法，可对第一分区内大麻哈鱼种群总量中的博南扎河贡献占比进行合理估算，进而近似得到该河的大麻哈鱼洄游个体总量。