Surgically Implanted JSATS Micro-Acoustic Transmitters Effects on Juvenile Chinook Salmon and Steelhead Tag Expulsion and Survival, 2010

The purpose of this study was to evaluate survival model assumptions associated with a concurrent study - Acoustic Telemetry Evaluation of Dam Passage Survival and Associated Metrics at John Day, The Dalles, and Bonneville Dams, 2010 by Thomas Carlson and others in 2010 - in which the Juvenile Salmonid Acoustic Telemetry System (JSATS) was used to estimate the survival of yearling and subyearling Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) migrating through the Federal Columbia River Power System (FCRPS). The micro-acoustic transmitter used in these studies is the smallest acoustic transmitter model to date (12 mm long x 5 mm wide x 4 mm high, and weighing 0.43 g in air). This study and the 2010 study by Carlson and others were conducted by researchers from the Pacific Northwest National Laboratory and the University of Washington for the U.S. Army Corps of Engineers, Portland District, to meet requirements set forth by the 2008 FCRPS Biological Opinion. In 2010, we compared survival, tag burden, and tag expulsion in five spring groups of yearling Chinook salmon (YCH) and steelhead (STH) and five summer groups of subyearling Chinook salmon (SYC) to evaluate survival model assumptions described in the concurrent study. Each tagging group consisted of approximately 120 fish/species, which were collected and implanted on a weekly basis, yielding approximately 600 fish total/species. YCH and STH were collected and implanted from late April to late May (5 weeks) and SYC were collected and implanted from mid-June to mid-July (5 weeks) at the John Day Dam Smolt Monitoring Facility. The fish were collected once a week, separated by species, and assigned to one of three treatment groups: (1) Control (no surgical treatment), (2) Sham (surgical implantation of only a passive integrated transponder [PIT] tag), and (3) Tagged (surgical implantation of JSATS micro-acoustic transmitter [AT] and PIT tags). The test fish were held for 30 days in indoor circular tanks at the Bonneville Dam Juvenile Monitoring Facility. Overall mortality ranged weekly from 45 to 72% for YCH, 55 to 83% for STH, and 56 to 84% for SYC. The high background mortality in all groups and species made it difficult to discern tag effects. However, for YCH, STH, and SYC, the Tagged treatment groups had the highest overall mean mortality - 62%, 79%, and 76%, respectively. Fungal infections were found on 35% of all fish. Mean tag burden for the Tagged treatment group was relatively low for YCH (1.7%) and moderate for SYC (4.2%), while STH had a very low mean tag burden (0.7%). Tag burden was significantly higher in the Tagged treatment group for all species when compared to the Sham treatment group because of the presence of two tags. Surgeon performance did not contribute to the difference in mortality between the Sham and Tagged treatment groups. Tag expulsion from fish that survived to the end of the 30-day experiment was low but occurred in all species, with only two PIT tags and one AT lost, one tag per species. The high background mortality in this experiment was not limited to a treatment, temperature, or month. The decreased number of surviving fish influenced our experimental results and thus analyses. For future research, we recommend that a more natural exposure to monitor tag effects and other factors, such as swimming ability and predator avoidance, be considered to determine the effects of AT- and PIT- implantation on fishes.