By Jeremy Kiszka
Madagascar is a major biodiversity hotspot for both terrestrial and marine ecosystems. However, this biodiversity is jeopardized by overexploitation, habitat destruction, and increasing threats such as climate change. Madagascar has a history of shark fisheries, particularly along the country’s west coast, which harvest the whole animal but include the export of shark fins to southeast Asia. Since the 2000s, shark populations have experienced significant declines in Madagascar. Since 2015, we have developed research activities on elasmobranchs (and other marine megafauna) in Madagascar, in collaboration with a number of local and international non-governmental organizations, as well as with government and local marine park authorities. Our research activities range from population assessments of reef sharks and rays to investigation on the ecology and behavior of whale sharks (Rhincodon typus). Last year we initiated the Global FinPrint project, the world’s largest standardized shark and ray survey, in Madagascar. Global FinPrint, funded by Paul Allen's Vulcan Philanthropy, aims to assess the diversity and relative abundance of sharks and rays in coral reef ecosystems around the globe (www.globalfinprint.org). Data collected will provide insight on the drivers of shark abundance (quantify environmental variables and anthropogenic effects) to identify “hotspots” and “darkspots”, and to produce management recommendations, including population restoration plans.
In March to July 2016, thanks to our local collaboration with NGO Baleines Asseau, the Wildlife Conservation Society (WCS), and the Tanikely Marine Park, we sampled 8 reef systems (400 BRUV drops) in northwestern Madagascar, particularly around the island of Nosy Be and surrounding islets and reefs. A staggering 13 species of sharks and rays were recorded, including globally endangered species like the scalloped hammerhead (Sphyrna lewini), which has been the subject of restricted international trade since 2013. Overall, we intend to sample the north and west coasts of the country, i.e. around 20 reefs (1000 BRUV drops), and conduct the first description of shark and ray communities in coral reefs of the coasts of Madagascar.
Global FinPrint sampling in Madagascar in 2016 and 2017... note that other reefs in other parts of the country might be added soon!
In April 2017, we performed the second phase of the Global FinPrint project in Madagascar surveying the western part of the country, where a major coastal shark fishing ground has been identified over the last years: the Barren islands. We are now leaving the island of Nosy Be for the largest ever conducted expedition to study sharks and rays in Madagascar! In order to explore the Barren Islands and since we needed a relatively spacious working and living environment, we embarked onboard “Antsiva”, a 28-meter sailboat with two smaller tenders used for deploying BRUVs, conducting diver surveys to assess fish communities, and more. It takes about 3 ½ days to get there…
Antsiva... heading south in the Mozambique Channel...
April 9-12: the commute
On our way to the Barren islands, besides getting the BRUVs ready for deployment, cetacean biologists and observers present onboard have been working intensively from the upper deck. Over these 3 days, while cruising south towards the Barren islands over the shallow waters of the continental shelf, we observed 5 groups of dolphins, including Indo-Pacific bottlenose dolphins (Tursiops aduncus) and pantropical spotted dolphins. Moreover, we have deployed a soundtrap to record large whale sounds, particularly from Omura’s whales (Balaenoptera omurai), a relatively common species along the NW
coast of Madagascar, but almost unknown at the global scale. The surrounding waters of Nosy Be and adjacent waters are the only known area in the world where these whales can be reliably found.
Dr. Sal Cerchio (New England Aquarium) extracting data from the hydrophone... On our way to the Barren, several species of cetaceans were recorded!
Over the last two days, we completed 50 drops in the most southern islands of the Barren islands: Nosy Lava and adjacent inlets. Our first sharks have been observed, and a new species for Global FinPrint Madagascar has been recorded: the sliteye shark (Loxodon macrorhinus). We have completed 4 dives during which 28 reef fish transects have been done, and our dolphin team has observed two groups of coastal dolphins, including Indo-Pacific bottlenose dolphins, and, for the first time in the Barren islands, the Indian Ocean humpback dolphin has been recorded! Over these last 2 days, we have also collected water samples for eDNA analyses. Thus, it is possible to trace the presence of elusive sharks and rays from this region by looking at the DNA they leave when passing through water masses in the coastal islands. About 25 liters of water have been filtered, and we hope to get amazing results soon!
|Sliteye shark (Loxodon macrorhinus)... a common species recorded in the Barren Island, but a new species for Global FinPrint in Madagascar!|
|Mark Bond and Jordan Goetze (WCS/Curtin University) with our stereo BRUV frames. These stereo systems allow us to calculate size of fish we sample.|
Christelle Razafindrakoto (WCS Madagascar)
Jeremy Kiszka filtering water to extract environmental DNA!
During our stopover in Nosy Lava, we also got a chance to meet and interact with Vezo fishers, who have established fishing camps throughout the Barren Islands. These fishers and their families generally come from Tulear, in the southwest, or from Maintirano, the closest town along the mainland coast of Madagascar. Since freshwater is a scarce resource on small coral islands, we brought drinking water to the first fishing camp we encountered. By interacting with the curious and friendly inhabitants, it gave us the opportunity to collect precious information on sharks and rays from fishers, who specifically target sharks, rays, and a variety of reef fish around the Barren islands. A variety of shark and ray species were observed drying up on the fishing camp, including spinner sharks (Carcharhinus brevipinna), scalloped hammerheads (Sphyrna lewini), zebra sharks (Stegostoma fasciatum), various stingrays, and guitarfishes. Thanks to their extreme kindness, we also got a chance to collect tissue samples of 12 giant guitarfishes (Rhynchobatus djiddensis)! What a great experience, and a truly productive time in Nosy Lava!
During visits of fishing camps in the Barren Islands... Here whitespotted guitarfish fins
Buying baits at the Fish Market!
Located further west off Nosy Lava, Nosy Andratra is a smaller island that we had to sample in one day. Thanks to great weather conditions, we have been able to complete 24 BRUV drops and 12 transect surveys. During a transect, we observed our first elasmobranch: a massive honeycomb stingray (Himantura uarnak)! A beautiful underwater encounter amongst really high fish densities. However, the water was sometimes very turbid, with a lot of zooplankton and important densities of jellyfish. Not surprisingly, we encountered a small leatherback turtle when deploying BRUVs! A number of reef sharks have also been seen on the BRUV, mostly grey reefs. In addition, we got a chance to visit a fishing camp on the tiny island, and 5 more giant guitarfish samples have been collected thanks to the cooperation of Vezo fishermen. Finally, we got a chance to conduct a small dolphin surveys, and 3 groups of Indo-Pacific bottlenose dolphins were encountered. Two biopsy samples were collected, and all individuals have been photographed for photo-identification purposes. Last, but not least, we collected water samples around the reef for eDNA analyses, what a productive day!
A beautiful bluespotted stingray!
Today, we sampled the surrounding waters of Maroantaly and “Croissant reef”, further north. When we got there, our first surprise was the really high turbidity of the water. At first, we were quite concerned since it could have had a serious impact on BRUV and underwater visual census data! However, we could deploy BRUVs on 30 occasions (our record!) and 6 transects have been completed. During the dive, despite a limited visibility, we have encountered the biggest pelagic fishes we ever saw during this expedition: large schools of kingfishes, giant trevallies, and more! We also observed several green turtles and a sleeping hawksbill turtle on the reef… what a dive! However, algae have significantly colonized the reefs here in Nosy Maroantaly (which might be due to the presence of large estuaries on the mainland, affecting some of the coral reef islands of the Barren by providing nutrients for the algae. Despite this, there was the presence of large patches of heathy coral reefs and abundant sponges. We also explored the island, but no fishermen were present. When surveying the beach, we found dozens of green turtle carcasses and remains. Vezo fishermen have a long tradition of turtle consumption, and these remains are not surprising to find. More surprisingly, we found a bottlenose dolphin skull on the beach. Dolphin hunting does occur along the west coast of Madagascar, and this discovery might reveal that the Barren islands could be a dolphin hunting ground (although some local experts think it might be rare). Another really interesting and productive day!
April 17 – Nosy Mavony
Today is marked by deteriorating weather conditions. The swell reaches 3 meters in some areas around the island, and it has been raining almost all day. Dives have not been possible, but, our BRUV team completed 24 drops and we have also been able to collect water samples for eDNA analyses. A single group of 9 bottlenose dolphins has also been encountered, but at the end of the day, we decided to leave the Barren islands due to a tropical depression that was developing in the Mozambique Channel to our south. Since a total of 126 BRUV drops have been completed in total in the Barren islands (a lot more than expected), we decided to leave the archipelago to retrieve the soundtrap tomorrow, and head to another archipelago located in the northwest, where no information on sharks and rays have ever been recorded: the Radama archipelago, south of the Nosy Be island complex. On our way, we will also observe cetaceans!
April 20 – Radama archipelago (1)
Over the last few days, we have been cruising along the northwest coast of Madagascar, looking for whales and dolphins. We also retrieved the soundtrap that we had deployed a week ago on the shelf off Cap Saint André, but no blue whale or Omura’s whale calls were recorded. However, we deployed the soundtrap on a few occasions on our way to the Radama archipelago… and we recorded a number of odontocetes (toothed whales and dolphins), including sperm whales, several species of dolphins, and most likely beaked whales. These sounds will be shortly analyzed by Dr. Cerchio to confirm species identity. This morning, the weather conditions are absolutely perfect to spot whales and dolphins. We encountered 3 groups of resting spinner dolphins (Stenella longirostris), and when cruising over reef banks of the Ramada, we also spotted stingrays and spotted eagle rays from the boat, beautiful encounters! Since we arrived a bit earlier than expected in the Radama (around 1pm), we decided to get started for BRUV and diver survey work. Our BRUV team hit the water, and deployed 12 BRUVs while our divers have completed 3 transects. The water here is so clear and the bathymetry is quite unique, so hopefully we will see lots of sharks and rays on the videos collected!
April 21 and 22nd – Radama archipelago (2)
Today, while the BRUV team was on the water, some crew members visited the first village (Antanimora) to interview a few fishermen on their fishing practices, including shark fishing and dolphin hunting. A number of shark remains have been found on the beach, including zebra, whitetip reef, silvertip, grey reef and sliteye sharks. It seems that sharks and rays are heavily fished in the Radama islands, but no dolphin hunting has been reported. After these interviews, diver surveys have been conducted on reefs where BRUVs have been deployed earlier in the morning. Reef fish abundance and diversity was absolutely stunning, with large endangered fish species encountered and high abundances of groupers, snappers, and other reef predators. The dive team also encountered a large school of humphead parrot fish, which are rarely observed globally so a real treat! After the dive, we also observed the largest group of Indo-Pacific bottlenose dolphin group ever documented in the SW Indian Ocean: 130-150 individuals together, all socializing! What an amazing day…
The next day, BRUV and dolphin teams were out again, collecting more videos and biopsy samples, respectively. At the end of the day, we were heading back to Nosy Be! What an amazing expedition… Overall, we have deployed BRUVs on 174 occasions, undertaken dozens of dives to assess fish assemblages, collected 50 eDNA samples across multiple reefs in the Barren islands and in the Radama, and considerable amounts of biological samples (particularly rays and dolphins) and other cetacean data. The west coast of Madagascar reveals its importance for an incredible number of species, including sharks, marine mammals and many others.
The lab will now pursue the FinPrint sampling further north with other local collaborators, and will develop more research activities in the countries. Stay tuned!