From 95 to 59 millimetres: 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 (U-crit; n = 241). Fish were implanted with a new active acoustic tag and compared with untagged controls at 12 and 17 degrees 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 U-crit 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.

Automated summary

The study showed that when the fork length of small Chinook salmon exceeded 58 mm, the survival and tag retention rates of tagged fish were very high, with no significant differences compared to the untagged control group. Additionally, the critical swimming speed of the control group and tagged fish were similar.