What is the effect of upwelling on activity levels of reef fishes in ecologically pristine site?

In the Agulhas Ecoregion of South Africa climate change is expected to result in increase in seawater temperature and an increase in the frequency and intensity of wind induced upwelling events. Upwelling events result in rapid (over period of hours) and large (e.g. 20 ºC to 9 ºC) drops in water temperature. Given favourable weather conditions these cold-water events persist for up to four weeks. Variation in water temperature is known to impact the metabolic rate of fishes and in turn their activity levels. Therefore, it is expected that increased frequency and intensity of upwelling may place the fish under significant physiological stress, ultimately impacting on their resilience. Baited remote underwater stereo-video systems (stereo BRUVs) can detect local changes in fish assemblage structure resulting from short-term changes in water temperatures. These changes typically manifest in reduced diversity and abundance. However, the relationship between water temperature and fish activity levels has not been tested previously. Using Chrysoblephus laticeps as the target fish species and indicator of activity levels (e.g. opercular beats, tail beats, feeding) that correlate with metabolic rate (e.g. respiration, energy availability) this project will aim to quantify the impacts of upwelling on fish behaviour from stereo-BRUVs collected in the Tsitsikama National Park Marine Protected Area.

Registered at: Rhodes University (Dept. Ichthyology and Fisheries Science)

Supervisors: Dr Anthony Bernard (SAIAB) and Dr Alexander Winkler (DIFS)