From 95 to 59 Millimeters: A New Active Acoustic Tag Size Guideline for Salmon
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 to untagged controls at 12 °C 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% 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.