Estuary update

By Sue Matthews, Overstrand Estuary Management Coordinator

The Bot River Estuary Forum (BREF) held its first official meeting on 30 June, following the launch in April, when Mr Nico Nasson was elected Chairman. Among the issues under discussion were the Overstrand Municipality’s Draft Growth Management Strategy, which proposes a densification zone of 20-30 dwelling units per hectare for the land currently occupied by the Lake Marina Yacht Club and public slipway. The Municipality’s Senior Town Planner, Hanneen van der Stoep, explained that any development would be subject to an engineering services feasibility study, as well as an environmental impact assessment (EIA). A number of BREF’s member organisations submitted comment on the proposals. 

Good news is that the Bot River estuary has been selected as the case study for a training exercise on applying the Department of Water Affairs’ Environmental Water Requirements method for estuaries using a Rapid RDM (Resource Directed Measures) study. The Rapid determination of the RDM is generally based on available information. The first step, once the estuary’s geographic boundaries have been delineated, is to describe the present state and estimate the reference condition, representing the natural, unimpacted characteristics and functioning of the system. This information is used to define the Present Ecological Status (based on a comparison between present status and reference condition), Ecological Importance and Ecological Sensitivity. These parameters are in turn used in the determination of the desired Ecological Management Class, as well as the water quantity component of the Reserve.  

A personal highlight was witnessing a Cape clawless otter making a meal of a large bird by attacking it in the shallows and then hauling it ashore to feed. Determined to get my feet wet and my hands dirty (or at least smelly!), I had joined a team of Marine and Coastal Management researchers for a day’s fish sampling on the estuary. As we headed across to the western shore of the estuary’s closed mouth in our skiboat, a flock of pelicans took off in a flurry and flew towards us. Then we noticed a commotion in the water, and watched as a large dark shape clambered onto the shore, dragging something behind it. Soon we were close enough to see it was an otter – and a rather boney one at that – with what appeared to be a dead pelican or cormorant. It looked as if it needed a good meal, so we kept our distance and left it to feed. 

Cape clawless otters are widespread in Africa, distributed over most of sub-Saharan Africa except for the Congo Basin, where they are replaced by a related species. There are an estimated 21 500 individuals in South Africa, but they are rarely seen because they’re either active at dawn and dusk, or completely nocturnal. They prey mainly on crustaceans such as crabs and rock lobsters, followed by fish and frogs, but they are opportunistic predators and will take any small animals that are available. Predation on waterfowl is uncommon, although domestic ducks and geese are often targeted. There are records, however, of Cape clawless otters attacking flamingoes in Kenya’s Lake Naivasha, and of North American river otters preying on brown pelicans in Rodeo Lagoon, in San Francisco’s Golden Gate National Recreation Area. The otters ambushed the pelicans from below, pulling them underwater or climbing on top of them and dragging them to a watery demise. 

I sent my photos to local otter expert Dr Michael Somers, now with the University of Pretoria’s Centre for Wildlife Management, and he agreed that the otter looked in poor condition, but noted that it was clearly strong enough to take on the bird, which could potentially inflict an injury. Or was it perhaps so desperate for food that it was prepared to take the risk, and in broad daylight too? One can only hope that its emaciated state is not a reflection of the estuary’s food web. 

Sue is contracted to the Overstrand Municipality in a position funded by WWF-SA and the Table Mountain Fund.