REDUCING HUMPBACK DOLPHIN BYCATCH IN THE SHARK NETS IN KWAZULU-NATAL
Shanan Atkins, Geremy Cliff and Neville Pillay
Endangered Wildlife Trust, University of the Witwatersrand, School of Animal, Plant and Environmental Sciences, KwaZulu-Natal Sharks Board, University of KwaZulu-Natal, Biomedical Resource Unit

 

Abstract
Humpback dolphins (Sousa plumbea) in southern Africa are classified as Vulnerable. One quantifiable threat is accidental mortality in the shark nets of KwaZulu-Natal. We investigated the spatial, temporal and life history patterns of this bycatch to guide mitigation strategies to decrease humpback dolphin capture. A total of 203 individuals were caught between 1980 and 2009. We analysed patterns of captures at 46 beaches by year and month of retrieval from the nets. We also analysed the distribution of the sex and size (body length) of captures. Most catches (61%) occurred at one beach, Richards Bay, where humpback dolphin population density may be relatively high. Annual catch rate fluctuated considerably with little seasonal difference. Adolescents constituted the majority of the catch (56%) and the overall sex ratio was male-biased (1.6:1). Mitigation strategies could be focused at Richards Bay, throughout the year. Our assessment of various existing shark net mitigation strategies shows that none is ideal but changing fishing gear from nets to baited hooks (drumlines) could be useful to decrease humpback dolphin capture rates. If a new mitigation strategy was developed it could target males or adolescent humpback dolphins.
Presentation Topic
REDUCING HUMPBACK DOLPHIN BYCATCH IN THE SHARK NETS IN KWAZULU-NATAL
Contact Ms Atkins:
Email Shanan Atkins