Paul J. Bentley¹, Kara E. Jaenecke², Joseph H. Vinarcsik², Matthew S. Morris³, Gabriel T. Brooks¹, Adam F. Palik².

1. Fish Ecology Division.  Northwest Fisheries Science Center.  National Marine Fisheries Service. NOAA.  520 Heceta Place, Hammond, Oregon 97121
2. Ocean Associates, Inc.  Under contract to Northwest Fisheries Science Center.  National Marine Fisheries Service.  NOAA.  520 Heceta Place, Hammond, Oregon 97121.
3. Astor Environmental LLC. Under contract to Northwest Fisheries Science Center.  National Marine Fisheries Service.  NOAA.  520 Heceta Place, Hammond, Oregon 97121.

In 2011, we installed a PIT-tag interrogation array on a sediment control structure (pile dike) in the lower Columbia River estuary investigating adult salmonid survival during upstream migration to Bonneville Dam.  Since then, we have installed three additional arrays constructed to detect tagged out-migrating juvenile salmonids.  Although these arrays were targeting salmonids, any PIT-tagged organism in the detection field is available for interrogation.  Presented here is a summary of white sturgeon, Acipenser transmontanus, detected at these four autonomous arrays since project inception.  To date, a total of 596 unique PIT-tagged sturgeon have been detected.  Our longest operating pile dike array (PD7), installed in 2011, has contributed the most, with a total of 519 (87%) unique tags, while the three other sites, installed in 2022 and 2023, had a combined total of 67 (11%) (PD5=54, PD6=9, and PD8=14).  Seasonal residency at these arrays, defined as remaining on site for more than a single day within a season, was observed in 5.4% (n=32) of the sturgeon detected.  Of these 32 fish, 7 were observed on the pile dikes for more than 30 days per visit. Site fidelity is also rare with only 27 individuals returning to the same site over multiple years, and 6 individuals returning over 5 years. The longest known resident has been detected each of the 12 years that PD7 has been operating, usually arriving in the last two weeks of May and residing through October, with an average residency time of 57.8 days.  During the seasonal residency at PD7, this sturgeon has been detected, near daily, on one or more antennas for the entirety of its visit..  The combination of transient and resident behaviors potentially indicates the transients are passing by on their way to a location of their own, where they potentially exhibit resident-like behavior with fidelity across years, similar to what is seen on PD7.  More pile dike arrays will be needed to evaluate this theory.  

Further expansion of these pile dike PIT-tag interrogation arrays for juvenile salmonid migrants will contribute additional information on sturgeon behavior in the coming years.