How effective is the De Hoop Marine Protected Area in protecting offshore reef fish populations?

By Richard Llewellyn (SAEON Elwandle Node; Rhodes University), Albrecht Götz (SAEON Elwandle Node) and Anthony Bernard (SAIAB) Tweet

The De Hoop Marine Protected Area (MPA) is a ‘no-take’ conservation area established in 1985 due, in part, to the presence of a South African military facility that restricted general access to the local marine environment.

Situated on the south coast of South Africa within the Western Cape Province, De Hoop is now the oldest and largest (253 km²) no-take MPA in the region.

Preparation (left) and deployment (right) of a baited remote underwater stereo-video system (stereo-BRUV)

Understanding the dynamics of the MPA

During the 30 years of the MPA’s existence, research has been limited and focused only on the inshore reefs which have provided little information on the status of the bulk of the park extending 5 km offshore. Understanding the dynamics of the MPA, especially with prominent fishing grounds close by (e.g. Struisbaai which is approximately 35 km from the western border), is crucial to its effective management.

To address this shortcoming, SAEON and Rhodes University initiated a project to assess the effectiveness of the De Hoop MPA in protecting the offshore reef fish populations. The project employed two approaches to attain a comprehensive picture of the status and temporal trends within and around the MPA.

The research boat Honckenii ready to be launched as the sun rises

Firstly, 27 years’ worth of fisheries catch data were analysed for patterns and trends in catches and spatial extent of preferred fishing grounds. This analysis was aimed at identifying whether or not the De Hoop MPA had benefited surrounding fisheries through increased catch rates or shifts of the preferred fishing grounds closer to the MPA.

Recording video footage

Secondly, fishery-independent data were collected employing baited remote underwater stereo-video systems (stereo-BRUVs) within the MPA and in areas near to the MPA (Struisbaai). The recorded videos allowed for precise abundance and size measurements to be obtained with the help of specialised software (EventMeasure^™). This software is particularly relevant in fisheries management as the biomass of fish resources can be estimated and applied in fisheries models.

Stills from stereo-BRUV footage. The bait container (at the end of the pole) attracts fish from the surrounding reef to within view of the camera. Some of the species visible in the stills include roman (Chrysoblephus laticeps), fransmadam (Boopsoidea inornata) and steentjie (Spondyliosoma emarginatum)

Overall, more than 100 hours of video footage were captured. As expected, not all videos were usable because of poor underwater visibility typical for the inshore waters along the South African south coast.

In the field, the research team enjoyed excellent support from the National Sea Rescue Institute (NSRI) at both Struisbaai and Witsand, as well as members of Cape Nature responsible for managing the De Hoop MPA.

Some of the commercially important reef fish found in the video recordings from the MPA included carpenter, roman, panga seabream, hottentot seabream, blue hottentot and other commercially less important species such as white stumpnose, fransmadam and steentjie.

Spearnose skate (Rostroraja alba - left) and spiny dogfish (Squalus spp.- right) get up close to the camera

Once all the data have been thoroughly analysed it should provide a clear picture of how effective the De Hoop MPA is in the protection of the offshore reef fish and its ability to provide benefits to the nearby commercial fisheries. The long-term aim of the research programme is to generate a complete bathymetric map of the MPA and establish annual monitoring of the fish communities within.