| Summary: | Biologists speculate that an increased population of harbor seals feeding on salmon smolts may have caused the observed decline in Chinook and Coho abundance in the Salish Sea. However, no method currently exists to accurately and effectively quantify seal predation rates of salmon smolts at the population scale. Passive Integrated Transponders (PIT tags) are often implanted in juvenile salmonids and used for population tracking and the determination of survival rates. Such PIT tagging efforts also provide a unique opportunity to assess the level of smolt predation by seals and sea lions. We have designed and built a prototype that contains electronics capable of identifying and logging PIT tags ingested by seals, and transmitting this information to a satellite. This prototype is battery powered and designed to be suitable for head-mounting to a harbor seal. Phase 1 feasibility testing aims to determine the capabilities of the prototype on captive harbor seals. Specifically, the detection rates for alternative PIT tag types (12mm, 23mm, HDX, FDX), and the length of time PIT tags are in the detection field during swallowing will be tested. This information will be used to determine the necessary RFID sampling rate/power consumption and guide the development of a field-ready instrument. The final prototype will be capable of logging the time and identification numbers of seal-ingested PIT tags, with the ability to transit that information via the AROGS satellite network. From those data, researchers will be able to accurately estimate smolt predation rates, and identify which individual stock is impacted by seal predation based on ingested PIT tag IDs.
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