Monitoring juvenile Chinook salmon outmigration using rotary screw traps on the Lower Feather River

CDFW issued Incidental Take Permit No. 2081-2019-006-00 (ITP) to the
California Department of Water Resources (DWR) on March 31, 2020,
for the long-term operation of the State Water Project (SWP) in the
Sacramento San Joaquin Delta (Delta). Condition 7.5.2 of the ITP
requires the development and establishment of a spring-run Chinook
salmon (Oncorhynchus tshawytscha) juvenile production estimate (JPE)
to increase understanding of the impacts that water operations have
on the spring-run Chinook salmon population in the Sacramento River
watershed and to inform the development of minimization measures to
reduce take of spring-run Chinook salmon at Delta fish salvage
facilities.  

As a part of the JPE effort, CDFW began operating a new rotary screw
trap (RST) monitoring station on the lower Feather River near River
Mile 17, approximately 1 mile downstream of Star Bend Park and Boat
Ramp near Olivehurst, in January 2022. This RST location represents
the lowest point in the Feather River Watershed where juvenile
salmon are sampled with an RST prior to entering the Sacramento
River and includes salmon emigrating from the Yuba River. The
expanded juvenile monitoring effort will help resource agencies and
water managers identify numbers of salmon emigrating from the
Feather River Watershed and contributing to the spring-run Chinook
salmon population entering the Delta.

Monitoring is conducted annually from October through June utilizing
a pair of eight-foot rotary screw traps (RST). Data collected at the
Lower Feather River RST site provides information on the temporal
distribution, relative abundance, and race composition of juvenile
Chinook salmon; and temporal distribution and relative abundance of
steelhead trout (O. mykiss) emigrating from the Feather River and
tributaries, including the Yuba River, to the Delta. Salmonid data
collected from the Lower Feather River RST, among other datasets, is
also used by the Salmon Monitoring Team (SaMT) to understand the
movement of juvenile salmon in the Sacramento River Watershed to
estimate the number of winter-run and spring-run Chinook salmon that
have entered the Delta. SaMT is a real-time operations monitoring
team required by Condition of Approval 8.1.2 of the ITP which meets
weekly from October through June, to provide advice for real-time
management of SWP operations to DWR, CDFW, and the Water Operation
Management Team (WOMT) to minimize take of winter-run and spring-run
Chinook salmon in the Delta.

Note: data within the current year’s monitoring season are
considered provisional.

2020年3月31日，加州鱼类与野生动物局（California Department of Fish and Wildlife, CDFW）向加州水资源部（California Department of Water Resources, DWR）签发了第2081-2019-006-00号附带捕捞许可（Incidental Take Permit, ITP），用于萨克拉门托-圣华金三角洲（Sacramento San Joaquin Delta，简称Delta）内的州水资源项目（State Water Project, SWP）的长期运营。该ITP的第7.5.2条款要求开发并建立春型奇努克鲑鱼（spring-run Chinook salmon，*Oncorhynchus tshawytscha*）幼鱼产量估算（juvenile production estimate, JPE）体系，以加深对水资源运营对萨克拉门托河流域春型奇努克鲑鱼种群影响的理解，并为制定减少三角洲鱼类救助设施对春型奇努克鲑鱼捕捞量的最小化措施提供依据。

作为JPE工作的一部分，CDFW于2022年1月在费瑟河下游靠近河道英里17处、奥利夫赫斯特附近的星弯公园与船坡道下游约1英里处，启用了一座全新的旋转螺旋陷阱（rotary screw trap, RST）监测站。该RST点位位于费瑟河流域的最下游区域，是幼鲑在进入萨克拉门托河前利用RST开展采样的点位，涵盖了从尤巴河（Yuba River）洄游而来的鲑鱼。此次扩展的幼鱼监测工作将帮助资源机构与水资源管理者明确从费瑟河流域洄游、并对进入三角洲的春型奇努克鲑鱼种群做出贡献的鲑鱼数量。

监测工作于每年10月至次年6月开展，采用两台8英尺旋转螺旋陷阱（RST）进行作业。费瑟河下游RST站点采集的数据可提供以下信息：奇努克鲑幼鱼的时间分布、相对丰度与类群组成；以及从费瑟河及其支流（包括尤巴河）洄游至三角洲的钢头鳟（steelhead trout，*O. mykiss*）的时间分布与相对丰度。除其他数据集外，费瑟河下游RST站点采集的鲑科鱼类数据还会被鲑鱼监测团队（Salmon Monitoring Team, SaMT）用于分析萨克拉门托河流域幼鲑的洄游情况，以估算进入三角洲的冬季型与春型奇努克鲑鱼的数量。SaMT是依据ITP的第8.1.2号批准条款设立的实时运营监测团队，于每年10月至次年6月每周召开会议，为DWR、CDFW与水资源运营管理团队（Water Operation Management Team, WOMT）的SWP实时运营管理提供建议，以最大限度减少三角洲内冬季型与春型奇努克鲑鱼的捕捞量。

注：本年度监测季内的数据均为暂定数据。