PNNL

Abstract

The Downstream Passage and Survival (Acoustic Telemetry) task was one of several tasks for the Evaluation of Howard A. Hanson Dam (HAHD) Juvenile Fish Passage and Survival study. For this task, a juvenile fish passage and survival study was conducted at HAHD from March 10, 2024 through June 27, 2024 for arrays in the HAHD Reservoir and Green River, and through July 9, 2024 for the arrays in the Duwamish River. Fish releases occurred over four times from March through May. Active tag (acoustic telemetry) technology was used to provide biological baseline information for the passage and survival of juvenile Puget Sound (PS) Chinook salmon (Oncorhynchus tshawytscha). Results will be used by biologists, engineers, resource managers, and regional decision-makers to inform the engineering design of the new fish passage facility (FPF) at HAHD. However, hatchery sub-yearling PS Chinook salmon of the appropriate size for tag implantation during the study period (> 95 mm in fork length, Geist et al. 2018) were unavailable. Therefore, yearling Coho salmon (O. kisutch) were used as a surrogate species for this acoustic telemetry study. This study was conducted by researchers from the Pacific Northwest National Laboratory (PNNL). The Juvenile Salmon Acoustic Telemetry System (JSATS) technology was used to evaluate existing HAHD operations to understand if they met the Biological Opinion (BiOp) requirements set forth by the National Marine Fisheries Service for fish passage (75% overall reservoir to downstream survival, 95% collection, and 98% passage survival; NOAA 2019). Additionally, a combination of reservoir elevation and discharge during spring refill was intended to be assessed, to evaluate at which depths and discharges were associated with (a) 80% fish passage in the reservoir, (b) 95% fish passage by the radial gate within the forebay, and (c) 2% mortality associated with the existing project passage. A total of 2,684 juvenile Coho salmon were tagged and used for analyses (n = 2,468 released alive; and n = 216 released dead). One of the primary findings from this study was that few fish were detected downstream of HAHD. There were 2,261 fish detected on the 3-dimensional (3-D) cabled array, located at the dam face of HAHD. Of those, 205 fish were detected downstream of HAHD. This is a conservative estimate because the 3-D tracking of fish for passage was unable to be performed. There was an overload of data on the autonomous and cabled receivers in the forebay of HAHD because fish were not passing the dam. The data overload caused data cards to fill up faster than expected, which led to data gaps and the inability to perform the 3-D tracking for fish passage. The data overload also created time jump issues in the data and caused strain on the batteries in the autonomous receivers. Finally, because so few fish were confirmed to have been detected downstream of the dam, fewer fish were tagged and released than were proposed. Another finding was that of the fish that were detected downstream of the dam, more did so earlier in the season (March) than later in the season (April and May). This could be attributed to the rise in reservoir elevation, which increased the depth fish would need to sound (dive) to find the outflow tunnel to pass the dam. As a result, the autonomous receivers and cabled array equipment were pulled from the reservoir before the battery life of the active tags expired, as it was anticipated the continued rise in reservoir elevation would result in even fewer fish passing HAHD and a continued overload of data on the receivers in the forebay. The joint probability of migration and survival for the March-released fish was estimated from fish release at the head of reservoir (HOR) to the Cumberland Kanasket Bridge (CKB), located approximately 14.3 river kilometers (rkm) downstream. Only fish released during the two March releases were used in this estimated because the battery life of their tags h