Training in shark population sampling in Tanga Using BRUVs

On March 13th 2017 representatives from Kenya and Mozambique set off by road from Mombasa on the Kenyan coast to Tanga, 175km south of Mombasa, in Tanzania, to learn how to use Baited Remote Underwater Video (BRUVs) for recording shark populations,  as a part of the Global FinPrint project. The travelers were myself, Clay Obota, and also Kennedy Osuka and Melita Samoilys from CORDIO, Benedict Kiilu from Kenya Fisheries Service and Gelica Inteca from Uni Lurio in Pemba, Mozambique. That evening we met at the Mkonge Hotel in Tanga with our three Tanzanian counterparts: Hassan Kalombo, the Regional Fisheries Officer, January Ndagala Acting Warden the Coelacanth Marine Park and Hakim Matola from TAFIRI in Dar es Salaam, as well as the lead trainer, Dr. Jordan Goetze, from Curtin University in Perth, Australia.

All the participants were guileless and eager to learn about BRUVs, in particular on how to analyze, interpret and utilize the data collected using the videos. Jordan kicked off the training with a day on land including lectures, discussions and hands-on practice with the equipment. The lectures covered how to survey fish abundance using BRUVs with detailed procedures on calibration, deployment and field data management. This was followed by hands on training setting up all the equipment ready for deployment. This consisted of 5 go-pro videos mounted in housings in a light aluminium frame or rig, and meters and meters of rope.

Based on the fact that most of us were novice in using BRUVs, this was set to be a hard day for Jordan our lead trainer but we went against all odds and managed to make 15 drops! Just like experts, we picked up the art so fast and continued dropping and lifting the BRUVs after every one hour and managed to deploy the BRUVs in two sites i.e. Nyuli (2 sets) and Mwamba Nyama (1 set). Seven connected reef systems were mapped and marked for sampling on the rocky and fringing reefs along the coast of Tanga, North of Tanzania. The success of the first was a clear indication of productive moments in the coming days and that actually the other days were a walk in the park with each team working efficiently with smiles and laughter lighting up the moments.

The team had picked up BRUVing well on the second day at sea, sampling the reef systems of Fungu Tangoni and Karange scaling up to 20 drops for the day. All the team players were on top of things in every department and it was work with smiling faces from the camera set up team, to bait preparation, to deployment and pick up of the camera frames out of the water.

We almost lost the one video frame due to strong currents on the 3rd day while sampling Karange and Jambe and had to pull it out and re-deploy it in shallower water. Mwamba Nyama, Mwamba Wamba and Chundo Kiroba reef systems were sampled on the 4th day in the sea with much success as deployment and retrieval of all 20 drops ended by 3.40pm, the fastest day since the beginning of the field trip – currents were low and video deployment went smoothly.

Chundo Kiroba and Mwamba Wamba reef systems were sampled on the 5th day. The team had gained the momentum to deploy the videos smoothly. However, the tides were strong and the last deployment for the day at Chundo Kiroba reef at a depth of 40m had to be retrieved and re-set at 35m since the currents were strong and the rigs were drifting. Even with the strong currents, the team managed to maintain 20 drops on this day as well.

On the 6th and last sampling day, the BRUV team worked without the trainer for a half day and managed 10 more drops giving a total of 105 drops against an initial target of 90 drops on Tanga’s reefs. This was a great achievement thanks to excellent team spirit and enthusiasm from everyone who picked up BRUVing fast and ran with it.

As we felt confident in the technique, the idea of using BRUVs as a tool for estimating population size of large fishes including sharks became increasingly popular across the participants from the three participating countries. The team is now looking forward to opportunities to take these skills acquired forward. CORDIO will be coordinating some sampling of reefs in Kenya and Mozambique later this year to estimate shark populations as part of the FINPRINT project.

    -Clay Obota, Research Assistant-