Comparative Performance of Acoustic-tagged and PIT-tagged Juvenile Salmonids

Numerous research tools and technologies are currently being used to evaluate fish passage and survival to determine the impacts of the Federal Columbia River Power System (FCRPS) on endangered and threatened juvenile salmonids, including PIT tags, balloon tags, hydroacoustic evaluations, radio telemetry, and acoustic telemetry. Each has advantages and disadvantages, but options are restricted in some situations because of limited capabilities of a specific technology, lack of detection capability downstream, or availability of adequate numbers of fish. However, there remains concern about the comparative effects of the tag or the tagging procedure on fish performance. The recently developed Juvenile Salmonid Acoustic Telemetry System (JSATS) acoustic transmitter is the smallest active acoustic tag currently available. The goal of this study was to determine whether fish tagged with the JSATS acoustic-telemetry tag can provide unbiased estimates of passage behavior and survival within the performance life of the tag. We conducted both field and laboratory studies to assess tag effects. For the field evaluation we released a total of 996 acoustic-tagged fish in conjunction with 21,026 PIT-tagged fish into the tailrace of Lower Granite Dam on 6 and 13 May. Travel times between release and downstream dams were not significantly different for the majority of the reaches between acoustic-tagged and PIT-tagged fish. In addition to the field evaluation, a series of laboratory experiments were conducted to determine if growth and survival of juvenile Chinook salmon surgically implanted with acoustic transmitters is different than untagged or PIT tagged juvenile Chinook salmon. Only yearling fish with integrated and non-integrated transmitters experienced mortalities, and these were low (<4.5%). Mortality among sub-yearling control and PIT-tag treatments ranged up to 7.7% while integrated and non-integrated treatments had slightly higher rates (up to 8.3% and 7.9% respectively). No acoustic transmitters were shed by yearling fish during the course of the 90 day study. Up to 7.8% of subyearling fish expelled transmitters. Tags were expelled from 5 to 63 days post-surgery. The average time to expulsion was 27 days; few fish expelled transmitters within 14 days of implantation or less. Histological results suggest that inflammation associated with implantation of an acoustic transmitter can produce fibrous tissue which can invade and possibly damage internal organs soon after implantation. Reactions severe enough to damage organs however, were limited to only ~20% of subyearling Chinook salmon, all of which were under 101mm and 12g at tagging. The infiltration of the fibrous tissue into organs was observed most often in fish held for 21 days and appeared to decrease in subsequent holding times