Comparing two methods of population estimation using Pyjama Catsharks (Poroderma africanum) of Mossel Bay, South Africa

The Pyjama Catshark, Poroderma africanum (Carcharhiniformes: Scyliorhinidae), is a coastal benthic species endemic to South Africa. Although it is not targeted in commercial fisheries, it is often taken as bycatch and caught by recreational anglers. Developing a better understanding of the population dynamics of this species is crucial to ecosystem health along the South African coast. Here, I compare two methods of population estimation for P. africanum in Mossel Bay, South Africa: mark-recapture and baited remote underwater video (BRUV) surveys. I calculated population estimations from each method and assessed the practicality, accuracy, and assumptions employed in statistical analysis and extrapolation. Overall, I found that BRUV survey analysis offers consistent, statistically sound population estimates (ranging from ~51 to ~136 individuals) with the added benefit of avoiding the physiological stress of conventionally captured animals. Thus, I advocate the continued use of BRUV surveys to monitor the population of P. africanum and encourage its use in population monitoring programs for other coastal species.