The Nature’s Valley Trust launched another exciting research project last week Thursday, monitoring fish in the Groot River Estuary. Initial fish surveys in the Groot River Estuary, conducted in 2010 by Kyle Smith and his team from SANParks, highlighted the estuary as an important nursery ground for a number of marine spawning species. The Groot River Estuary is regarded as a sanctuary for estuarine resident fish species, as well as marine migrant species such as the endemic Cape Stumpnose. The Groot estuary also plays a role in hosting endangered species such as the estuarine pipefish, the over-exploited and vulnerable White Steenbrass, Leervis and Spotted Grunter. The Nature’s Valley Trust (NVT) is now continuing this monitoring project for the next five years, under Kyle Smith’s guidance, to determine both the structural and functional properties of the estuaries fish community.
Kyle instructing the NVT team on what needs to be done.
The Groot River estuary is a small temporarily open/closed system, that is, periods of tidal interchange (open mouth) alternate with periods of no interchange (closed mouth). The estuary falls under management and protection of the Tsitsikamma section of the Garden Route National Park. This river is just outside the western boundary of the Tsitsikamma Marine Protected Area (MPA) no-take zone. This project involves quarterly sampling at six sites along the estuary to get a representative idea of the fish using the estuary each season.The type of gear used for sampling is a 30m seine net approved by SAIAB andDAFF as the standardised sampling gear. Captured fish are placed in buckets containing estuarine water, identified, counted, measured and released. Fish length, measured as snout to tail fork, is measured to the nearest mm. In cases where numbers of fish caught are too large, measurements are restricted to sub-sampling to prevent mass mortalities. During sampling, water quality parameters are measured using a YSI multi-probe that NVT acquired through funds generated from Magnetic South’s Otter Trail Run.
Minke and Kyle rowing the net out
During our first survey last week Thursday, we sampled a variety of species. Amongst these were the endangered White Steenbrass, the vulnerable Leervis, Blackhand Sole, endemic Cape Stumpnose and indicator species such as the Longsnout pipefish. The Longsnout pipefish was sampled at site 1 (our closest site to the mouth of the estuary) of the estuary. Longsnout pipefish are regarded as indicator species which help to indicate the health of the water body as these live close to the bottom sediments which trap pollution and heavy metals, thus indicative of relatively good water quality.
Babalwa and Yola taking water readings with NVT’s YSI probe
Overall, it was a great day, with lots of interesting fish to see and handle! Sampling of all these important fish species on the day further highlighted the importance of estuaries, in particular, the Groot River estuary as a ‘haven’ for marine migrant species as well as other estuarine resident fish species. Preceding the 2010 survey, the Groot River estuary had little known and/or available scientific data with regards to its ecology or biology. We are therefore excited to have launched this research project and hope that this research will benefit the Park and its management, as well as the public.
Now the hard work…pulling in the net
NVT team at work!