From 95 to 59 millimetres: a new active acoustic tag size guideline for salmon

Abstract

Two laboratory studies evaluated small Chinook salmon (Oncorhynchus tshawytscha) (36–99 mm fork length (FL), 0.7%–26.7% tag burden) survival, tag retention, and growth (n = 539) and critical swimming speed (Ucrit; n = 241). Fish were implanted with a new active acoustic tag and compared with untagged controls at 12 and 17 °C. Across studies, no temperature differences were detected. All control fish survived. All tagged fish ≥58 mm FL survived and retained their tags. Regression models predicted ≥98.6% survival and retention for tagged fish ≥58.6 mm FL or ≥1.9 g (4.2% tag burden). No growth differences among treatments were identified. Spline regression analysis indicated Ucrit was similar for control and tagged fish that measured ≥57.3 mm FL. We recommend tagging salmon ≥59 mm FL or ≥1.9 g (≤4.2% tag burden), although the guideline should be confirmed in a field setting. Study results represent an important step towards using the new active tag in acoustic telemetry field studies that estimate short-term (30-day) survival of small salmonids.