Ocean mission to keep track of shark movements
WILDOCEANS research vessel RV Angra Pequena, carrying a team of researchers and marine students, set sail for Protea Banks on the south coast of KwaZulu-Natal in order to retrieve telemetry receivers previously deployed in the area.
The retrieval of these receivers or listening stations will give ocean experts the ability to investigate the movements of tagged sharks and highlight the importance of canyon heads as a critical shark habitat.
These receivers pick up and record unique signals from acoustic tags inserted onto tagged fish and sharks and allow researchers to track the movement patterns of these species.
These acoustic listening devices were deployed from RV Angra Pequena in July at 80m to 90m depths at the head of each of the three big submarine canyons that lie seaward behind the Protea Banks reef system, within the newly announced marine protected area (MPA).
The devices were part of a national Acoustic Telemetry Array Platform (Atap) managed by the SA Institute for Aquatic Biodiversity (Saiab) and made up of a network of acoustic receivers that were strategically deployed at stations all along the coast.
WILDOCEANS executive director Dr Jean Harris said the study was the first of its kind in South Africa and one of only a few worldwide.
“The aim is to study the movement of sharks along the KwaZulu-Natal coast.
“This part of the project that is led by Dr Matt Dicken of the KwaZulu-Natal Sharks Board, aims to understand the importance of canyon heads as critical habitat for sharks, especially species such as tiger, ragged-tooth and Zambezi,” Harris said.
“We are especially interested in understanding the role submarine canyons play as productive nodes in the seascape and the connectivity with shallower inshore habitats.
“The receivers that we retrieved and replaced are deeper in 80-90m of water at canyon heads.
“Due to the depth of these sites, the receivers have acoustic releases, which can be remotely activated from the surface by a boat,” he said.
In December and January, WILDOCEANS undertook a scalloped hammerhead shark survey in Protea Banks.
“As this species has only been tagged in Mozambique to date, if we picked up any signals for this species on our receivers this would show that there is a connection between sites in Mozambique and this big aggregation in southern KwaZulu-Natal, and that the sharks are moving between them,” Harris said, expressing that the team would be excited if they were recorded on the Protea Banks receivers.
Youth for MPAs representative and Ocean Steward Jamila Janna, whose role on the expedition is to help spot the buoys attached to the equipment when it surfaced, said: “Seeing how many components there are to marine biology and also just spreading the message of conservation – it’s fun and I just love learning.
“I really like experiences like this and love this kind of work.”