Tsitsikamma Rivers and Estuaries Program

The focus of our river and estuary research is to study the unique, near pristine systems we have in and around Nature’s Valley. We are collecting data on the pressures and threats to the fish stocks in the Groot River Estuary - that functions as a refuge and breeding ground for many local fish species. This important program has several projects linked to it:


Groot River Estuary Fish project

Estuaries are regarded as one of the most productive environments on earth, and are known to support a number of estuarine-dependant endemic species. We monitor marine fish use of the Groot River Estuary in collaboration with SANParks, netting fish 4 times a year to assess which species utilize the estuary. This enables us to determine both the structural and functional properties of the estuaries fish community, providing an effective method of assessing the estuaries ecological condition. We tag and release fish there too. The estuary has been identified as a key nursery ground for the endemic Cape Stumpnose, and also plays a role in hosting endangered species such as the estuarine pipefish, the over-exploited and vulnerable White Steenbrass, Leervis and Spotted Grunter.


Groot River Estuary Mosquito Fish Monitoring project

During fish sampling in 2011, SANParks surprisingly found the invasive mosquito fish in the Groot River. Gambusia affinis is a fish species that originates from the eastern and southern United States river systems. In the early 1900s these fish were distributed throughout the world as a biological control measure to curb mosquito populations. As a result, this fish species is one of the most widely distributed fresh water species in the world today, and is now listed as one of the world’s worst alien invasive species. NVT is currently running a monitoring project, in conjunction with SANParks, to determine the population structure and relative abundance of Mosquito fish in the Groot River estuary. This study will also look at the potential influence of physical/abiotic and biotic factors on these components, that is assess water quality parameters as well as other organisms potentially interacting with this fish species. Whilst sampling in the estuary it has become evident that Mosquito fish hot-spots are the littoral zones of the estuary, generally in muddy areas or those with submerged vegetation. Sampling is conducted in eleven selected sites along the stretch of the estuary and will involve monthly sampling to assess seasonal abundance and distribution.

mosquito fish

These above two fish projects are made possible through annual funding from Magnetic South, from funds raised during the Otter Trail run – widely known as the “grail of trail”!


Bird monitoring

CWAC (Coordinated Waterbird Counts): We survey the Groot River tributaries  and Estuary for waterbirds on a biannual basis. This data gets fed into a database tracking our species and assists with waterbird conservation in South Africa.