A team of UCT scientists equipped with a state-of-the-art underwater camera, is currently working in deep water near Port Nolloth to test the impact that trawling may have on typically trawled seabed.
The team, headed by UCT associate professor, Colin Attwood, and accompanied by an engineer from the fishing industry, is conducting its experiments using the South African research vessel, Ellen Kuzwayo as a platform. Photographs and video footage are being gathered near the edge of the continental shelf at a depth of approximately 480m using a newly acquired Ski-Monkey submersible camera. A benthic grab is being deployed to collect samples of sedimental biota (infauna).
The voyage of the Ellen Kuzwayo forms part of a three-year collaboration between the South African Deep Sea Trawling Industry Association (SADSTIA); the University of Cape Town (UCT); the South African Environmental Observation Network (SAEON) and the Department of Agriculture, Forestry and Fisheries (DAFF). Its goal is to obtain a scientific understanding of the environmental impact of hake trawling in South Africa.
“Naturally, we know that trawl gear impacts the seabed,” says Roy Bross, Secretary of SADSTIA, “but we need to uncover more about the extent and consequences of impacts depending on the nature of the sea bottom.”
“In South Africa, hake trawling occurs almost entirely on soft, muddy, sandy or gravelly sediments and even though the size and weight of trawl gear is strictly regulated it is important to document the effects.”
The three-year experiment will allow scientists to compare photographs and footage of trawled and untrawled zones, and assess the characteristics of the seabed in both areas. In preparation for the voyage of the Ellen Kuzwayo, the trawling industry closed a small part of the trawling grounds known as Karbonkel for a period of a year.
“The experiment will allow us to get a better understanding of a specific trawled marine ecosystem and to assess the rehabilitation rate for fallow ground on typical trawl footprint,” says Bross.
Gaining better insight into the impacts of trawling will enable SADSTIA to improve its environmental performance. In 2004, the Association was among the first in the world to successfully apply for certification from the Marine Stewardship Council (MSC) and it has retained this prestigious endorsement ever since. The industry body has also initiated projects to reduce interactions between seabirds and fishing gear, limit the industry’s environmental footprint and instituted new rules to better control the retained catch of monk and kingklip caught in bottom trawling operations.
“This seabed research is part of our environmental responsibility and an action that contributes to the retention of MSC certification,” said Bross.
