Matthew S. Morris¹, Kara E. Jaenecke², Joseph H. Vinarcsik², Paul J. Bentley³, Gabriel T. Brooks³, Adam F. Palik²

1. Astor Environmental LLC (under contract to NOAA Fisheries NW Fisheries Science Center), 520 Heceta Place, Hammond, OR 97121
2. Ocean Associates, Inc. (under contract to NOAA Fisheries NW Fisheries Science Center), 520 Heceta Place, Hammond, OR 97121
3. NOAA Fisheries, 520 Heceta Place, Hammond, OR 97121

In 2011, we began developing methods to install PIT tag antennas on flow control structures- pile dikes- in the Columbia River estuary to target detections of adult salmonids. Acoustic camera surveys showed more adult activity on the downstream side of pile dikes, guiding our initial antenna placement.

The stationary interrogation concept was first developed on a spur dike (oriented 90 degrees to flow) near RKM 70 on a site labeled “PD7” in PTAGIS. Continued development through the 2010’s saw various iterations of antenna construction and placement to improve detection efficiency of PIT-tagged fishes along the dike. Since the initial phases of the project, changes in management objectives in the basin and water management of spill programs highlighted the importance of juvenile salmonid detection in the estuary to complete Federal Columbia River Power System reach survival estimates.

Beginning in 2022, we expanded this concept to a site across the river from PD7 on a training dike (~45 degrees to flow) to take advantage of the streamlined flow created by the structure. We paced antennas along the upstream side at the lower terminal end of the dike to target detections of juvenile salmonids. This site, PD6, detected 3,076 fish in its first year of operation, with juvenile salmonids comprising 96% of detections. In contrast, the estuary PIT trawl, which is the primary source of juvenile detections in the estuary, detected 9,662 juvenile fish during the same period.

Based on 2022 results, we further expanded pile dike detection in the estuary to encompass two new training dikes in 2023. PD5 was 8 km downstream of PD7 and adjacent to the thalweg. PD8 was 12 km upstream of PD7 and constructed on a training dike where the thalweg was closer to the opposing shore. All four sites were autonomous and included a solar array, charge controller, and batteries, cellular communication, a PIT transceiver, and at least four antennas placed on the upstream side of the dike. Since each location presented unique challenges based on river location, flow, debris loading, and distance from vessel moorage, individual sites were uniquely constructed based on the needs of each location.

In 2023, PD5 detected 7,462 fish of varying species, runs, and life stages, PD6 6,735, PD7 820, and PD8 725.  After accounting for duplicate detections between pile dike sites, this interrogation method detected 15,549 unique fish.  During the juvenile salmonid outmigration season (1 April to 15 June), it detected 12,228 fish compared to the PIT Trawl’s 9,485 fish.  We will continue our expansion in 2024, taking lessons learned from each site to further increase estuary detection and contribute to hydrosystem survival estimates and other studies that include the species and life stages detected by the pile dike arrays.