We continued research and development of a passive PIT-tag detection system along a pile dike in the estuary (rkm 70). Target fish for this system are returning adult salmonids, whose detection in the mid-estuary can be compared with subsequent detections at upstream dams to determine timing and survival during the adult migration. In 2013 we changed all system electronics from the MUX used in 2011 and 2012 to the MTS transceiver. This system upgrade allowed us to quadruple the size of antennas, and thus fish passage openings, to an area of 2.4 6.1 m. In March, we installed three new antennas encased in a rigid PVC housing (10 cm diameter) onto the pile dike system (PTAGIS site code PD7). One of these eventually leaked, and we replaced it in July using an antenna with an experimental housing. The new housing was smaller in diameter (19 mm) and made of flexible PVC hose. We expanded the system with 2 additional antennas placed further inshore along the pile dike (5 total). Except for interruptions to replace antennas and a few brief interruptions in late fall due to solar power shortage; the new system has remained operational from March through October 2013.

In 2013, we detected 375 adult and jack salmonids including 96 spring Chinook, 104 summer Chinook, 106 fall Chinook, 54 steelhead, 12 sockeye, and 3 coho salmon. We also detected 612 juvenile salmonids, 5 sturgeon, 1 pikeminnow, and 32 fish with PIT tags yet to be identified in PTAGIS. Survival estimates (SE) of adults to passage over Bonneville Dam were 90.5% (15%), 88.2% (8%), 92.1% (5%), and 90.7 (8%), respectively for spring, summer, and fall Chinook salmon and steelhead. Median travel times from detection at PD7 to Bonneville Dam for the same fish groups were 4.0d, 3.7d, 3.2d and 4.6d.

Stationary PIT-tag antennas are used to interrogate PIT-tagged fish throughout the Columbia River hydrosystem and in streams to evaluate fish passage and survival for both juvenile and adult fish. Pile dikes are common in the estuary and in some areas located less than 0.5 kms apart and can be a substantial obstacle for migrating fish along the shoreline. Fishermen often utilize the area near pile dikes to target adult fish believing they become more concentrated as they circumvent the outermost piling during their upstream migration. This strategy was similar to that used in the late 19th and early 20th centuries by designers of effective fish wheel leads utilized with great success until banned. Estuary PIT-tag data obtained with a pair-trawl characteristically shows an increase in detection rate of juvenile fish when passing just outside of these pile dikes. In fall 2011 and continuing through fall 2012, we deployed a 4 to 6-coil configuration of detection antennas using an industry standard MUX transceiver system (site code PD7 in PTAGIS). Fish passage openings were limited to 4X10 with the MUX but we created a matrix of coils spanning 8.5 X 20 in water 20 deep. In 2013, we adapted a Bata version of a new IS1001 transceiver system and deployed antennas with individual coils as large as 10X 20 in the same location. We propose continued deployment of stationary PIT-tag antennas on representative pile dikes to evaluate the potential of establishing a network of stationary monitoring sites in the estuary for long-term data collection. A proto-type Pile Dike Antenna (PDA) system deployed near river kilometer 70 since 2011 has enabled collection of limited timing and species composition data for adult salmonids (primary target) entering the estuary and juvenile salmonids (secondary target) exiting the estuary. Expansion of such antenna systems to passively sample passing fish at various fixed locations in the estuary enable calculation of survival rates to Bonneville Dam for adult salmonids to better evaluate impacts by marine mammals. PDAs would potentially provide full year detection capability for both adult and juvenile salmonids in the estuary. .