Harvey

Another day, another milestone

CORDIO samples Tanzania

FinPrint Spotlight


Author: Clay Obota, MSc

Organization: CORDIO East Africa

Biography: Clay joined CORDIO as an intern working under the Fishery Aggregating Devices project and advanced to a research assistant working on marine biology/ecology, fish population dynamics, fish stock assessment, and fisheries management.

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 do baited remote underwater video surveys (BRUVs) to record shark populations as a part of the Global FinPrint project. The travelers were myself, Clay Obota, 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 of 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 how to analyze, interpret, and use the data collected from 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 for deployment. This consisted of five GoPro cameras mounted in housings on a light aluminium frame or rig, and meters of rope.

Since most of us were new to using BRUVs, this was set to be a hard day for Jordan, but we worked against all odds and managed to do 15 drops. Just like experts, we picked up the science quickly. After multiple one hour deployments, we managed to deploy the BRUVs at two sites: 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 day was a clear indication of future productivity. The following days were a walk in the park where each team worked efficiently with smiles and laughter lighting up the experience. 


From bait preparation to BRUV deployments and pick-ups, everyone worked hard as a team on the second day of sampling the reef systems of Fungu Tangoni and Karange, where we set 20 BRUVs. We almost lost one video frame due to strong currents on the third day while sampling Karange and Jambe. We had to pull it out and redeploy it in shallower water. Mwamba Nyama, Mwamba Wamba, and Chundo Kiroba reef systems were successfully sampled on the fourth day, with the deployment and retrieval of 20 BRUVs before 4pm, the fastest day since the beginning of the field trip thanks to low currents and smooth deployments.

Chundo Kiroba and Mwamba Wamba reef systems were sampled on the fifth day. Although the team was eager to deploy as many BRUVs as the previous day, the tides were strong making this goal challenging. The last deployment for the day at Chundo Kiroba reef was set to a depth of 40m. It 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 last sampling day, the BRUV team worked without Jordan for a half day. The team completed 10 more drops for a total of 105 drops over the course of the entire sampling trip, 15 drops more than the initial target of 90 on Tanga’s reefs. This was a great achievement thanks to the excellent team spirit and enthusiasm from everyone who learned efficient BRUV techniques.

As we felt confident in this methodology, 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 countries. The team is now looking forward to opportunities to use these acquired skills. CORDIO will be coordinating reef sampling in Kenya and Mozambique later this year to estimate shark populations, again as part of the Global FinPrint project.

Global patterns of shark and ray bycatch

Publication specs

Title: Global patterns in the bycatch of sharks and rays

Authors: Shelby Oliver, Matias Braccini, Stephen J. Newman, Euan S. Harvey  

Journal: Marine Policy

Year: 2015

The left-behind, the unwanted, the unmanaged – whatever you want to call it, bycatch is prevalent in commercial fisheries. Sharks and rays are at risk of becoming bycatch in all commercial fisheries. So what exactly is bycatch? Bycatch is the discarded (dead or alive) catch and/or unmanaged catch from fisheries. While fishing for particular species, fishers often catch unwanted species using longlines, trawls, gillnets, and purse-seines. It is common for these so-called undesired species to be illegally kept and later sold, particularly in the case of some sharks and rays, whose fins sometimes end up in the lucrative fin trade.

This study reviewed relevant data from global commercial fisheries. Most of the data came from the North Atlantic Ocean, which is not where the majority of fishing occurs. This suggests that most fisheries are not effectively reporting bycatch data. Shark bycatch mainly occurred in the South Atlantic pelagic longline fishery. No patterns were found in ray bycatch, likely due to a lack of data reporting. For both sharks and rays, the largest total annual bycatch took place in pelagic longline and deep sea/coastal trawl fisheries. One shark species dominated longline bycatch – the blue shark, pictured above – which may make up more of the catch than the actual target species. Rays are not exempt from unregulated fishing, and as a group are considered more threatened than sharks. Perhaps even more alarming is that the majority of ray bycatch comes from commercial trawl fisheries where they are often thrown back into the ocean, left for dead. 

Below is an overview of the prevailing species caught as bycatch by region:

screen-shot-2016-10-17-at-11-16-46-am


Sharks

  • Blue sharks – North & South Atlantic, Western Pacific
  • Silky & thresher sharks – Indian Ocean & Eastern Pacific

Rays

  • Pelagic rays – South Atlantic, Western Pacific & Indian Ocean

Sharks

  • Sharpnose sharks – North Atlantic
  • Dogfish – South Atlantic, Eastern & Western Pacific
  • Carpet sharks – Indian Ocean

Rays

  • Skates – North & South Atlantic


Sharks

  • Blacktip shark – North Atlantic
  • Sevengill sharks & shortnose spurdogs – Indian Ocean
  • Catsharks – Eastern Pacific

Rays

  • Cownose rays – North Atlantic
  • Bat rays – Indian Ocean & Eastern Pacific


Sharks

  • Coastal sharks (e.g. blacktip, bull, and dusky sharks) – North Atlantic & Eastern Pacific
  • Silky sharks – South Atlantic & Indian Ocean

Rays

  • Manta & devil rays – South Atlantic, Eastern Pacific & Indian Ocean


These results suggest that global shark and ray bycatch monitoring – data collection and availability – should become high priority for management. Sharks and rays are important fishery and tourism resources, especially in developing nations, so it is vital to find out if these levels of bycatch are sustainable for each species. Should the current levels of shark and ray bycatch in commercial fisheries not be sustainable, regulations would have to be modified or developed and enforced to safeguard their future.

Mozambique Mission 2016

FinPrint Spotlight

                                                                      Anna FlamAlexandra Watts

In August, the Global FinPrint team headed to Mozambique to assess the marine life found on the reefs around Vilanculos and Bazarut Archipelago National Park. Anna Flam (left) and Alexandra Watts (right) from the locally based Marine Megafauna Foundation joined the team to deploy baited underwater videos (BRUVs). Alexandra Watts reports from the field.

The Marine Megafauna Foundation (MMF) has been researching large fish such as sharks and rays in southern Mozambique for over 10 years. So we were really excited when the Global FinPrint research team invited us to help them with the reef assessment in this beautiful and biodiverse part of Mozambique. The goal of this collaboration was to complete half the BRUV drops inside the Bazaruto Archipelago National Park and half outside, to look at the differences inside and outside the protected area. After the equipment arrived from Australia, we began setting up the BRUVs by securing frames, legs, GoPro housings, ropes, buoys and floats, batteries – these had to stay dry until ready for use.

central-mozambique-aug-2016

The first day, we waddled down to the beach; each laden with various bits of the BRUV kits, and loaded them onto the boat with the help of Zito, our local skipper. We were aiming for the northern end of the archipelago and dropped around ‘Spaghettis’ and ‘Three trees’ – reefs on the northeast side of Bazaruto Island. Luckily, the weather was on our side and we were able to drop here for several days. By day 3 and 4, the weather had closed in a little and so we stayed closer to Vilanculos, on our second site at Two Mile reef.

Photo: Alexandra Watts

Photo: Alexandra Watts

After the first few days, we eagerly waited as the experienced BRUVers Conrad Speed and Jordan Goetze downloaded all the footage and replayed it. The footage was fantastic. Moon wrasse, yellow snapper, red fanged trigger fish, sailfin tangs and a giant guitarfish were just part of a kaleidoscope of species of all shapes and colour. Within the first day the guys had noticed something they had never seen before; schooling Moorish idols. They saw this species in Australia and other locations but never in such huge numbers before. Moray eels took a particular interest in the bait bags, grabbing them and death rolling to get access to the fish, while an octopus and a blotched fantail ray just sat on top of the entire bag, preventing anything else from getting access.

moorish-idols

Moorish idols surround bait bag

BRUVs are a useful tool to collect data on marine species composition and information such as this can be communicated to local government. Sampling is often done using underwater surveys. However, BRUVs are especially useful for avoiding biases with these techniques such as behaviour changes by species in response to a diver carrying out video surveys. This is important when carrying out species counts – fish which actively avoid divers may cause a species to be completely omitted from a study, resulting in an inaccurate account of species within an area. It is also an efficient census technique – they don’t require skilled divers in the water and all the associated risks and technical equipment. They can be left on the seafloor without an operator, simply with a marker nearby to make it easy to find them, whilst further work can be continued elsewhere.

Technically, this is an advantage. But, after reviewing some of the footage, we wish we had been there to see it with our own eyes – not only did we have visits from both reef and giant manta rays but also smalleye stingrays, round ribbontail (aka blotched fantail) rays, pink whiprays, Jenkins’ whipray, spotted eagle ray, bull sharks, blacktip sharks, blacktip reef sharks, grey reef sharks, and whitetip reef sharks.

We were also specifically looking out for dugongs, which are one of the only herbivorous marine mammals in the world and rare inhabitants off the coast of Africa. This animal is extremely sensitive to anthropogenic threats such as gill netting, hunting, pollution, habitat loss, and coastal development. Population numbers have been drastically reduced in East Africa. The Bazaruto Archipelago population is now possibly the only viable population in Africa, and the second largest in the Western Indian Ocean. And, although we didn’t manage to see one face to face, we did get a couple of glimpses of these curious animals on BRUVs!

A dugong casually swims past one of the BRUVs.

Analysis of the footage is (understandably) time-consuming and will take a little longer until we can begin to summarise the findings. It was an absolute pleasure for Anna and myself to be involved in this study and we hope it paves the way for further collaborations of this nature. The more marine scientists can connect and work together on both international and regional projects, the more efficient research becomes. Human pressures have exerted such a huge threat to so many forms of marine life that the oceans are reaching a breaking point. Targeted conservation initiatives – informed by projects such as this – are the only way we are going to begin to make a difference.

Conrad carefully drops the BRUV. Photo: Alexandra Watts

Conrad carefully drops the BRUV. Photo: Alexandra Watts