Using biotelemetry to assess the mortality and behaviour of yellowfin bream (Acanthopagrus australis) released with ingested hooks

Butcher, P. A., Broadhurst, M. K., Orchard, B. A., and Ellis, M. T. 2010. Using biotelemetry to assess the mortality and behaviour of yellowfin bream (Acanthopagrus australis) released with ingested hooks. – ICES Journal of Marine Science, 67: 1175–1184. Biotelemetry was used to test the hypotheses of few impacts to yellowfin bream (Acanthopagrus australis) released with ingested hooks. Sixteen sample fish were tagged and tracked (using 18 receivers), along with 32 controls (16 pre-tagged “C1” and 16 simultaneously tagged “C2” fish) for 112 d in Botany Bay, Australia. All fish survived initial release, but seven tags from two C1, four C2, and one hook-ingested fish remained motionless within the first 6 d, and another 23 fish were last detected near the release site (a fish farm). Most disappearances were attributed to recapture by anglers or predation. The latter fatalities were exacerbated among controls, and they possibly resulted from the confounding effects of confinement, including a loss of fitness. Such effects were limited to the first 4 d; after which all fish had similar movements. Most (98%) subsequent detections were within 1 km of the fish farm, likely attributable to the associated habitat and abundant food. Although all fish remained near structures, 18 fish travelled farther. In addition to providing the first fine-scale information on the movements of yellowfin bream, the study validates releasing hook-ingested individuals with the line cut as a means for minimizing mortality.