Movements and growth rates of bronze whaler sharks (

Abstract

Context Sharks that are targeted by recreational anglers and commercial fisheries can be vulnerable to overexploitation when fishing effort is not informed or regulated by data on relative distribution and growth. Aims To understand the spatiotemporal distribution, movement patterns, and growth rates of bronze whaler sharks (Carcharhinus brachyurus) in southern Africa. Methods Tag–recapture records derived from a 36-year cooperative shore-angling program were compiled and analysed using non-parametric Kruskal–Wallis tests and a Francis growth model. Key results Distribution was centred in Namibia and the South Coast of South Africa during the austral summer. Large-scale regional movement supports the lack of population structure in southern African. The South Coast of South Africa represented a potentially important nursery region where 93% of juveniles were tagged. Subadults and adults were more widely distributed and recorded a significantly greater time at liberty than were juveniles, but the distance moved for adults was significantly lower, indicating higher site fidelity. Growth model predictions showed that annual growth rates of C. brachyurus were among the slowest compared with other carcharhinids. Conclusions and implications These slow life-history traits, affinity to coastal regions and cross-border movements leave the southern African C. brachyurus population vulnerable to overexploitation in the absence of regionally aligned research and management.