Movement patterns and underestimation of the maximum age of a Vulnerable endemic guitarfish species inferred from mark-recapture studies

Abstract

Data collected from mark-recapture programmes have proven invaluable in assessing the movements and growth of numerous fishery species along the South African coastline. This short note reports on tag and recapture information on the Vulnerable endemic lesser guitarfish Acroteriobatus annulatus. This species appears to exhibit site-affinity behaviour, with an observed mean distance moved of 38.5 km (SD 121.4, range 0–726 km). The recapture of two individuals (tagged as adults; ∼100 cm total length) 6 and 12 years after tagging suggests that the maximum age for this species is likely more than double the current maximum recorded age of 7 years (estimated from vertebral ring counts). This has major implications for the management of this bycatch species (with a declining population trend), and for other guitarfish species occurring in South Africa for which the maximum age is currently unknown.