Lochsa River Instream PIT Tag Detection Systems

Worksite #1 – Lower Lochsa River PIT-tag Array
Installation of the Lower Lochsa River PIT-tag Array was completed in October of 2016. The site included 14 – 20 ft instream antennas. The site was fully operational for steelhead and Chinook spawn year 2017. With completion of the site, the entire Lochsa River drainage was monitored for adult steelhead and Spring/Summer Chinook escapement. Installation of the array provided 70 miles of mainstem habitat monitoring plus full monitoring of additional tributary habitat miles. For the purpose of metric reporting only the mainstem Lochsa River was included in monitoring metrics. Since only one span was completed as of spawn year 2017 array efficiency estimates were not calculated for spawn year 2017 and escapement estimates were considered minimum estimates based on unexpanded PIT-tag interrogations at the site. The site also provides 70 miles of mainstem habitat and additional miles of tributary habitat monitoring for juvenile steelhead and Chinook migration timing and survival for fish tagged in the Lochsa River drainage.

Worksite #2 – Upper Lochsa River PIT-tag Array
Installation of the Upper Lochsa River PIT-tag Array was completed in September of 2017. The site included 18 – 20ft instream antennas. The site is fully operational for steelhead and Chinook spawn year 2018. With completion of the site, the entire Lochsa River drainage was monitored for adult steelhead and Spring/Summer Chinook escapement with a dual array system (upper and lower Lochsa River arrays). Installation of the array provided 70 miles of mainstem habitat monitoring plus full monitoring of additional tributary habitat miles. For the purpose of metric reporting only the mainstem Lochsa River was included in monitoring metrics. Installation of both upper and lower mainstem Locsha River arrays now provides the ability to estimate array efficiency in the Lochsa River drainage and expanded estimates of adult steelhead and Chinook abundance will be available for spawn year 2018 and into the future. The site also provides 70 miles of mainstem habitat and additional miles of tributary habitat monitoring for juvenile steelhead and Chinook migration timing and survival for fish tagged in the Lochsa River drainage.

Recent advancements in Instream PIT-tag detection system technology have allowed adult escapement estimates into some drainages (South Fork Clearwater River and South Fork Salmon River) by expanding PIT-tag detections at tributary arrays based upon the tag rate at Lower Granite Dam. High priority areas such as the Lochsa River and Selway River are currently not outfitted with Instream PIT-tag detection systems and adult escapement estimates into these areas are unknown. This creates significant data gaps for monitoring these wild B-run areas. Based upon size criteria (>775mm) counts of steelhead at Lower Granite Dam, B-run steelhead have declined significantly from previous decades and have not responded as have wild A-run populations which have shown modest increases in abundance in the past decade. Increasing knowledge and understanding of trends within wild B-run stronghold such as the Lochsa River a high priority for co-managers throughout the Columbia River Basin.

To date, limited information (Fish Creek, Lochsa River IDFG) has been collected on wild B-run steelhead within Idaho. This is especially true for adult steelhead abundance in specific populations. The collection of data from Fish Creek in the Lochsa provides index level data for the Lochsa Population, but does not capture the entire Lochsa Population. The 2014 Final Supplemental FCRPS Biological Opinion indicated the Lochsa Population was identified as requiring a 16% habitat quality increase and commensurate increase in steelhead survival, which will be achieved through habitat restoration actions within the Lochsa drainage. Installation of the Instream PIT-tag detections system and existing monitoring infrastructure to monitor juvenile production will provide the assessment for these future efforts.