Effects of T-bar and DST Tagging on Survival and Growth of European Hake

Abstract

Controlled experiments were conducted to assess the effects of T-bar and DST tagging on post- release survival and growth of European hake. In this study, two groups of each 30 hake were considered: small fish (SF, average total length: 29.9 cm ± 2.2 cm) and large fish (LF, average total length: 36.4 cm ± 2.5 cm). Within each size group, fish were randomly assigned to one of 3 treatment groups: control (C), T-bar tagging referred as conventional tagging (CT) and DST tagging (DST) with dummy tags. After 4 months, the overall survival rate was 35%. Smaller fish were less impacted by the stress induced by handling, anaesthesia and tagging and in the SF group, the survival rates were similar (30%) for CT or DST. Specific growth rates were highly variable and no significant difference could be observed between control and tagged fish. Our results demonstrate that (1) conventional tagging affects fish survival rates and (2) DST tagging is feasible in the field on “small fish” with expected survival rate and recapture probability close to that of conventional tagging.