The effects of surgically implanted acoustic transmitters on laboratory growth, survival and tag retention in hatchery yearling Chinook salmon

Telemetry has proven an effective means for studying the movement of fishes, however, biases associated with tagged animals requires careful scrutiny if accurate conclusions are to be made from field studies. The objective of this study was to evaluate growth, survival, and tag retention in hatchery yearling Chinook salmon (Oncorhynchus tshawytscha) juveniles with intracoelomic surgically implanted acoustic transmitters representing 2.6 to 5.6% of body weight. The first trial consisted of three treatments; passive integrated transponder (PIT) tag-only (25 fish), acoustic-tag+PIT-tag (25 fish), and sham-surgery+PIT-tag (25 fish). There were no significant differences in relative growth rate (% change in weight day(-1)) among treatments over the 221 day trial. Survival in the acoustic-tag treatment (80%) was not significantly different from the PIT-tag-only and sham treatments (92 and 88% respectively). The second trial consisted of three treatments; PIT-tag-only (22 fish), acoustic-tag+PIT-tag with absorbable sutures (12 fish) and acoustic-tag+PIT-tag with non-absorbable sutures (12 fish). There were no significant differences in relative growth rate among treatments over the 160 day trial. Survival in the second trial was 100%. Fish with absorbable sutures healed sooner and with less inflammation compared to fish with non-absorbable sutures. Tag retention was 100% in both trials. The results of this study suggest that acoustic transmitters of less than 5.6% body weight can be effectively used in 1-year old Chinook salmon.