Samantha Ockhuis

PhD Candidate
Samantha Ockhuis


Genetic connectivity of the slinger Chrysoblephus puniceus in South African east coast Marine Protected Areas.

Marine Protected Areas (MPAs) sustain fisheries and conservation but they also preserve areas of cultural significance, generate aesthetic and educational benefits (Edgar et al. 2007). MPAs have been studied successively (Halpern 2003, Lester et al. 2009), however the extent of their effectiveness remains poorly understood. In South Africa MPAs as in many other parts of the world have shown to enhance reef fish abundance and diversity (Buxton and Smale 1989, Bennett and Attwood 1991, Currie et al. 2012, Floros et al. 2013, Kerwath et al. 2013). MPAs not only serve as a tool for fisheries management, but also for the maintaining of coral cover (Selig and Bruno 2010).

The slinger Chrysoblephus puniceus is a protogynous hermaphrodite, maturing first as female and later reproducing as male, with female maturation at 3 years and sex change occurring after 5 years (> 240 mm) (Garratt 1985, Garratt et al. 1993). Chrysoblephus puniceus is endemic seabream, inhabiting the coastal reefs of the southwest Indian Ocean (southern Mozambique, Natal and northern Transkei) and an important line-fish species in South Africa and Mozambique, with spawning occurring mainly off the coasts of Mozambique and northern Natal (mostly to the north of Durban) (Garratt 1985). Chrysoblephus puniceus are highly resident, however it was found through tagging studies in the Pondoland MPA, that some adults do migrate in a north-easterly direction (Maggs et al. 2013). Duncan et al. (2015) found a panmictic stock and high levels of connectivity from southern Mozambique to the southern Transkei using mitochondrial and microsatellite markers. It was also indicated by Duncan et al. (2015) a high likelihood of southward dispersal by prevalent ocean circulation acting on the larvae.

The aim of this study is to examine the connectivity of C. puniceus between three MPAs, namely; iSimangaliso Wetland Park, Aliwal Shoal and Pondoland as well as the surrounding areas. The genetic structure and connectivity of C. puniceus will be examined using a “reduced representation” genome sequencing approach – restriction site associated DNA sequencing (RADseq) for Single-nucleotide polymorphism discovery and genotyping. Fin clips of 40-50 adult slinger will be sampled from each from each of five localities (iSimangaliso, Thukela, Durban, Aliwal Shoal and Pondoland), roughly 100-150 km apart, in 2018. To determine sources of recruits to southern MPAs, roughly 50 one-year old fishes will be sampled from the Aliwal and/or Pondoland MPAs early in 2019 and 2020. Repeat sampling will allow examination of annual recruitment variability and reproductive input. By determining the connectivity of functionally important east coast fauna in existing/proposed MPAs, we will be able to determine these MPAs more than just conserve their inhabitants.

Registered: Rhodes University (Department of Ichthyology and Fisheries Science)

Supervisor: Dr. Gavin Gouws (SAIAB)
Co-Supervisor: Dr. Sean Fennessy (Oceanoraphic Research Institute)