Stunning images open a window on the deep-sea world

Stunning images of the fishes and marine life living on or close to the seabed nearly half a kilometer under the sea, have been gathered by University of Cape Town (UCT) scientists working with a submersible camera off the west coast of South Africa.

The scientists collected the images in the first of a series of surveys that will test the environmental impact of hake trawling in South Africa.

Their investigations are the result of a three-year collaboration between the South African Deep Sea Trawling Industry Association (SADSTIA); UCT; the South African Environmental Observation Network (SAEON) and the Department of Agriculture, Forestry and Fisheries (DAFF).

Chief scientist Colin Attwood of UCT, led a team of scientists and technical specialists that included post doctoral student, Charles von der Meden (SAEON); doctoral students, Karen Tunley and Steward Norman of UCT; Driaan Pretorius, ship manager of Viking Fishing and electronics technician, Xolani Methu (DAFF).

“The water was perfectly clear at a depth of 360 to 510 m,” said Attwood, adding that the remarkable images of hake, jacopever, skates and an unusual type of “spiny eel” were probably the first of their kind ever taken in South Africa.

To capture the images, the scientists deployed a submersible Ski-Monkey camera mounted on a steel sled. The camera was towed behind the research vessel Ellen Kuzwayo at carefully plotted positions. At each deployment, the camera captured 10 minutes of still photographs and 10 minutes of video footage of the seabed and the organisms living on or just above it.

A Van Veen grab was used to collect samples of the benthic macro-fauna (invertebrates like worms, crustaceans and bivalves that live on or in the sediments).

From March this year, hake trawlers will no longer trawl in the experimental block where the photographs, video images and sediment samples were taken. The 6 x 15 nautical mile block is part of the trawl grounds known as Karbonkel, situated near the edge of the continental shelf off the Northern Cape town of Port Nolloth.

“The intention is to repeat the survey in subsequent years so that we can determine whether there is a recovery in benthic life,” said Attwood.

“With cooperation from SADSTIA-affiliated trawlers, the closure should provide an excellent test of the ability of the trawl grounds to recover. The surveys will increase our understanding of the biodiversity in this environment, and the effects of depth and trawling–related disturbance.”

The trawling industry is enthusiastically supporting the experiment, with the chairman of SADSTIA, Tim Reddell, saying it is vitally important for the industry to better understand the impact that fishing has on the environment.

“The more information we have, the easier it is for SADSTIA to consistently improve the environmental footprint of the fishery,” said Reddell.

“This experiment is just one of the projects that SADSTIA has initiated over the past ten years in an effort to meet and exceed the exacting standards of the Marine Stewardship Council (MSC).

The South African deep-sea trawl fishery was the first hake fishery in the world to be certified by the MSC as a sustainable and well managed fishery. It has retained this prestigious endorsement ever since.