Wind River Subbasin Restoration Annual Report of USGS Activities January 2021 through December 2022

We sampled juvenile wild Steelhead Trout Oncorhynchus mykiss in headwater streams of the Wind River, WA, to characterize population attributes and investigate life-history metrics, particularly migratory patterns, and early life-stage survival. We used passive integrated transponder (PIT) tagging and a series of instream PIT-tag interrogation systems (PTISs) to track juveniles and adults. The Wind River subbasin is considered a wild Steelhead refuge by Washington Department of Fish and Wildlife (WDFW). No hatchery Steelhead Trout have been released in the Wind River subbasin since 1997, and hatchery adults are estimated at less than one percent of spawners in most years. Over twenty years of Steelhead Trout status and trend monitoring and research in the subbasin is contributing to understanding of population response to numerous restoration actions in the subbasin, including removal of Hemlock Dam from Trout Creek in 2009, which had an outdated adult ladder and contributed to increased water temperatures reducing performance of juvenile Steelhead Trout.

Data from our study, and companion work by Washington Department of Fish and Wildlife, are contributing to Bonneville Power Administrations (BPA) Research, Monitoring, and Evaluation (RM&E) Program Strategy of Fish Population Status Monitoring (https://www.cbfish.org/ProgramStrategy.mvc/Index). Specifically, this work addresses the sub-strategies of 1) Assessing the Status and Trends of Diversity of Natural Origin Fish Populations and Uncertainties Research regarding differing life histories of a wild Steelhead Trout population, 2) Assessing the Status and Trend of Adult Natural Origin Fish Populations, and 3) Monitoring and Evaluating the Effectiveness of Tributary Habitat Actions Relative to Environmental, Physical, or Biological Performance Objectives.

During summer and fall 2021 and 2022, we PIT-tagged 1,889 and 1,391 Steelhead parr (age-0 and age-1), respectively, in the Trout Creek and upper Wind River watersheds. Age-0 parr were at lower densities in 2022 than many years due to a poor return of adult Steelhead spawners in 2022. Steelhead Trout parr were recaptured and detected through repeat headwater sampling, smolt trap operations, and instream PTISs and Columbia River PIT-tag detection infrastructure. We maintained, and upgraded in 2022, a series of six instream PTISs to monitor movement of tagged Steelhead Trout parr, smolts, and adults, providing data to population assessments, and life-cycle research and modeling.

We continue to improve our PTISs in the Wind River subbasin. The improvements in siting and addition of grid power to the upper Wind River PTIS (site code WRU, rkm 27.6) during 2016 and 2017, and the addition of the Mine Reach site (site code MIN, rkm 36.0) have much improved PIT-tagged fish monitoring in the upper Wind River watershed. The paired PTIS design in the upper Wind River watershed (sites WRU and MIN) matches that in the Trout Creek watershed (sites TRC, rkm 2.0; and TC4, rkm 11.5) and will allow comparisons of Steelhead Trout population metrics between the two watersheds as response to Hemlock Dam removal continues and future restoration efforts occur in Trout Creek.

During summer 2022, we upgraded three PTISs with new transceivers and new or reconfigured antennas. We replaced the Biomark 1001 Multiplexing Transceivers with Biomark MTS IS1001 Master Controller and individual IS1001 Transceivers at WRU, TRC (Trout Creek, rkm 2.0), and TC4 (Trout Creek at 43 Road Bridge, rkm 11.5). These new transceivers and antennas will improve detection performance due to increased read range and decreased susceptibility to noise. We also installed an additional IS1001 Transceiver and 11-foot antenna at WRA in summer 2021 to increase cross-channel and water column coverage.

Detection data from PIT-tagged adult Steelhead Trout at PTISs allow assessment of adult escapement to tributary watersheds within the Wind River subbasin. Adult Steelhead Trout detection efficiency estimates at our primary PTIS in Trout Creek have been greater than 99 percent during six of the past eight years and have exceeded 97% at our primary PTIS in the Wind River during seven of the past eight years. Adult escapement estimates to tributary watersheds are helping us evaluate the efficacy of the 2009 removal of Hemlock Dam from rkm 2.0 of Trout Creek. The dam had potential negative effects on Steelhead Trout populations in Trout Creek due to hydrologic impairment, increased temperatures, and adult passage issues. Hemlock Dam was laddered for adult passage, but not to modern standards, which likely resulted in avoidance by some adult Steelhead Trout.

Detections at the instream PTISs have demonstrated trends of age-0 and age-1 parr emigration from natal areas during summer and fall, in addition to the expected movement of parr and smolts in spring. We have estimated that from 15 to 51% of parr tagged as age-0 fish in headwater areas make downstream migrations at age 1 for additional rearing. Downstream movement occurs primarily during spring but also in fall. We have estimated that up to 27% of Steelhead Trout parr, tagged as age-1 fish, make downstream migrations during fall. Fall migration of age-1 parr has been more common in the upper Wind River watershed than the Trout Creek watershed. These findings raise questions about where parr most successfully rear and whether migrations are density- or habitat-quality driven. Broader monitoring programs would give a more comprehensive understanding of juvenile Steelhead Trout production and rearing and contributions to adult recruitment from varied rearing strategies.

Repeat sampling at consistent locations in the subbasin has enabled assessment of juvenile Steelhead Trout growth patterns. Growth rates (relative change in weight) of age-0 PIT-tagged parr during summer were similar across the subbasin, though slightly lower in the Trout Creek watershed. The greatest summer growth rate was in the mainstem of the Wind River (rkm 37 and 41). Summer growth rates were lower for age-1 parr in the Trout Creek watershed than the upper Wind River watershed. Yearly relative growth was similar across the subbasin for both age-0 and age-1 tagged parr. Lower Layout Creek had the highest yearly growth rate of parr from age-0 to age-1. Mainstem Wind River (rkm 37) had the highest yearly growth rate of parr from age-1 to age-2.

Non-native Brook Trout Salvelinus fontinalis are present in the subbasin, chiefly the Trout Creek watershed, and repeat sampling provides an index of their prevalence. Mean percent-of-catch that is Brook Trout, at four sample sites in Trout Creek, has declined from the period 1998 2003 to the period 2011 2022. Percent-of-catch and number of Brook Trout at the Trout Creek sites from 2011 through 2022 has generally declined, though both metrics have been somewhat variable.

Evaluation and planning of habitat restoration efforts are critical to ensure efficient use of money and resources. Assessing Steelhead Trout life history variation in the Wind River subbasin will inform research and tracking of many populations and help inform habitat restoration and water allocation planning. Movement of Steelhead Trout parr from natal areas to other rearing areas raises questions regarding juvenile abundance, origin, and habitat use within watersheds. Improved PTISs and focused PIT-tagging of age-0 and age-1 Steelhead Trout parr allow investigation of such questions. Increasingly detailed viable salmonid population information, such as that provided by PIT-tagging and instream PTIS networks like those in the Wind River, can provide data to inform fisheries policy and management and understand life-history strategies and limiting factors. Such efforts also enable assessment of long-term effects of habitat restoration actions such as the removal of Hemlock Dam on Trout Creek, and the proposed Stage-0 restoration effort for upper Trout Creek, which would be a large-scale effort to reset sections of stream within their floodplain, restoring connectivity and interaction with surrounding landscape.