Effects of tag and suture type on survival and growth of brown trout with surgically implanted telemetry tags in the wild

To test the effects of surgical implants with or without external antennae, 188 wild brown trout Salmo trutta , 150–290 mm, were tagged and released in a small river in May 2005. After 5 months, 103 of the fish were recaptured and examined. Thus, information on the relative survival, growth and general condition of each fish was obtained. The relative survival did not differ between the three groups (control, antennae and no antennae), but the specific growth of the two tagged groups were lower than that of the control fish. The tag:body-mass ratio had a significant negative effect on specific growth. A relative high occurrence of tag expulsion was observed in both treatment groups (23%). The probability to expel a tag was correlated with the tag:body-mass ratio. Finally, the relative survival, growth, expulsion rate and general condition were compared between fish tagged with different types of suture material (absorbable v . non-absorbable). The results show only minor differences, but absorbable suture provided better wound healing and fewer expulsions.