Capturing footage of our amazing marine wildlife
Our last activity for this week was to drop some BRUVs in the waters around Dyer Island. BRUVs (or Baited Remote Underwater Videos use GoPros attached to metal structures with bait canisters to record the species in an area. When dropped into the water they sink; sardines in the canister give off a chum slick attracting the fish in the area to the bait and into the GoPros field of view. One can then review the footage and see what species are in that vicinity.
BRUVs are relatively cost effective and capable of detecting species richness, taxonomic diversity, frequency of occurrence. While being somewhat limited by water visibility and light penetration, their usefulness vastly outweighs these.
As a result, BRUVs have been increasingly used for monitoring marine parks worldwide. They have allowed for the phasing out of other less effective or more damaging techniques such as netting/trapping, SCUBA based underwater visual census, and explosives/ichthyocides. We learnt all this in a brief lecture prior to the trip, as well as being briefed on the standard procedures of BRUV deployment.
Using BRUVs ourselves
On Friday afternoon we loaded Lwazi, the small research vessel, with the BRUVs and our bait fish then took to the water to find our drop off points. Our Skipper, Francois, located predetermined coordinates in areas around Dyer Island. These were chosen by Cape Nature (a government organisation which is responsible for maintaining wilderness areas and public nature reserves in the Western Cape), and then we deployed the BRUVs.
The locations had to be the same as previous deployments as replication is essential to gathering accurate data. We deployed 4 BRUVs in total, and each one was to film for one hour before retrieval. Being on the boat was also a good opportunity to practice basic boat safety and skills such as knots and man overboard drills, which we recapped earlier in the week. Footage from the BRUVs will be sent to Cape Nature however we can also take a look at it and identify the species seen. Our focus will be on the small sharks (cat sharks and shy sharks), skates and rays that come to the bait.
The sunset boat ride back to the harbour was the perfect end to a very busy week and we look forward to seeing what exciting activities next week will hold!