Devil Sharks: Science Behind the Show

26 July 2017

With volcanologist Jess Phoenix at Ocean Entry

Scientists studying the active volcano of Kavachi in the southwest Pacific got a real surprise when they found sharks living inside the caldera a few years ago.

When you first think about sharks and volcanoes few would expect a special attraction — including me. But I was asked about exploring the links between the two, I was intrigued. For the last two years I’ve been part of the Global FinPrint project — a worldwide effort to survey shark and ray populations on coral reefs that is supported by Paul G. Allen and Vulcan, Inc. I realized that many of the coral reefs we’re working on, and where we see lots of sharks, have volcanic origins.

During the research and filming for Devil Sharks, which premieres at 10 p.m. tonight on Discovery Channel’s Shark Week, we had the opportunity to extend some of the lab's projects, meet and work with amazing scientists from around the world, and learn a lot about volcanoes. Special thanks to Volcanologist Jess Phoenix for showing us around the Big Island of Hawaii’s volcanoes — by both air and sea! 

So what do we know about the relationship between sharks and volcanoes?

A Nice Place to Call Home

Whitetip reef shark under a ledge.

At the most basic level, one thing that makes volcanoes important for sharks (and many other species) is that they create a comfortable habitat — maybe not for us, but certainly for sharks. Even before volcanic activity has created land that pushes above the surface of the ocean, seamounts form and are a place where all kinds of animals congregate. 

As islands form, so will many different habitats. In warm waters, coral reefs pop up to create shallow habitats near shore. For some sharks, the shallow waters and even old lava tubes of volcanoes can provide safety from predators. For many sharks, volcanoes provide food, and for others a convenient rest stop. Without question, volcanoes create secure environments in the middle of the ocean where sharks can thrive.

Different species of sharks at different life stages are found in each of these habitats. Because many volcanic islands have steep slopes, open ocean sharks can be found close to shore, providing researchers with great opportunities to study hard-to-find species. During our trip it was great to catch up with Dr. Melanie Hutchinson and see her work on the pelagic sharks you find close to shore off the Kona coast of the Big Island.

With Dr. Jeremy Kiszka (center) and Dr. Eric Clua (right)

Frances Farabaugh preparing to sample for Global FinPrint

Once volcanoes become dormant and islands start to erode away, the volcanoes are still great places for sharks. The shallow waters of lagoons are a perfect place for small sharks to grow up, keeping them safe from larger sharks that would like to eat them. 

Work we have done in the islands of French Polynesia, though, suggests that there might be a scramble for food in these nurseries. When baby blacktip reef sharks and baby sicklefin lemon sharks are found together, their diets change — probably because of competition.  

Throughout French Polynesia, FIU Ph.D. candidate Frances Farabaugh is sampling reef sharks as part of the Global FinPrint project with Dr. Jeremy Kiszka and Dr. Eric Clua. Some of their work is featured in Devil Sharks. We’re examining how the differences between islands impact the types and numbers of sharks present. We’re also collecting tissue samples to figure out where different species of sharks feed — along the reef, in the lagoon, or in the open ocean — and we are working with Eric to track silvertip sharks.

But wait, what about the heat?

When volcanoes are active and lava is flowing into the water, it creates patches of very warm water. Is warm water part of what attracts sharks to active volcanoes?

Unfortunately, we just don't know. But, we do know that lots of species of sharks and rays move between warm and cold waters (aka behavioral thermoregulation) to help with foraging, digestion and possibly reproduction. With warm waters available, it’s certainly possible that sharks use water around active volcanoes in the same way they use other pockets of warm water.

Magnetic attraction?

One question many scientists are interested in is how sharks navigate in what appears to be a completely featureless ocean. Shark tracking has shown that they can swim in nearly straight lines from one island to the next over huge distances. 

One possibility is that they use variations in the magnetic field. Work by Carl Meyer, Kim Holland, and James Anderson of the University of Hawaii tells us sharks have an impressive magnetic sense. Using trained baby sharks, they’re now conducting experiments that could help us understand just how small of a difference in magnetic fields they can detect. 

Lava pouring into the ocean off Hawaii.

Around volcanic islands and features, the strength of the magnetic field can change quite a lot. Here is a neat example from New Zealand. Could sharks use this variation to find their way to and from volcanic islands? Studies of sharks in the wild suggest that they could. Peter Klimley found that the hammerhead sharks he tagged off the coast of Mexico appeared to use variation in the magnetic field to move to and from seamounts.  

Do sharks use magnetic fields to navigate over large distances? Researchers are still working on it! Using satellite tags to track movements of many individual sharks — like we did off Saba Island in the Caribbean — is one way to find out.

Papers:

Meyer CG, Holland KN, Papastamatiou YP. 2005. Sharks can detect changes in the geomagnetic field. Journal of the Royal Society Interface 2: 129–130.

I hope everyone enjoys the show! Thanks to Pangolin Pictures for the invitation to participate.  Also a huge thanks to all who worked on the documentary and those who have supported the research depicted in the film, especially Paul G. Allen, Pangolin Pictures, Divers Direct, Atomic Aquatics, and Exeye Ltd.

BARREN Expedition – Investigating reef sharks and rays in the coastal waters of Madagascar

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! 

                                                             Cameras charging...  

April 13-14: Nosy Lava

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! 

April 15 - Nosy Andratra

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! 

April 16 – Nosy Maroantaly

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!

Green turtles and invasive seagrass mission continues in Martinique and Guadeloupe

By: Vincent Quiquempois and Elizabeth Whitman

Once again, the Heithaus lab returned to Martinique and Guadeloupe, of the French West Indies, to collect data on the effect of an invasive seagrass, Halophila stipulacea, on the distribution and feeding behavior of green sea turtles. Our team, Ph.D. candidate Elizabeth Whitman, Dr. Jeremy Kiszka and research intern Vincent Quiquempois, was excited to get back into the water with our many collaborators and conclude our turtle and seagrass surveys for this portion of the project.

We first landed in Martinique where we met with our collaborators from the Réseau Tortue Marines de Martinique, Marie-Fance and Maxym. They offered to assist us with our surveys for the entire week we will were in Martinique! To estimate the density of sea turtles, we conducted snorkel surveys along transects throughout the bay of Grande-Anse located in the South west part of Martinique in Les Anses d’Arlets. We recorded sightings of all turtles within the transects and collected additional data on feeding behavior, seagrass assemblages and other megafauna. On this trip, we were even lucky enough to see an eagle ray during one of our transects!

Left: green turtle swims over bed of Halophila stipulacea; Right: fragments of Halophila stipulacea, like this one floating by a mooring, are capable of colonizing new areas

For a more detailed study of the seagrasses and algae found in the bay, we estimated abundances of each species within quadrats and collected samples for nutrient analysis back at FIU. For the shallow part of the bay, we managed to free dive to realize our objectives but for the deeper part, we used SCUBA. During these dives, we also saw some interesting marine life!

Elizabeth Whitman (left) and Jeremy Kiszka (right) conduct
detailed surveys of the seagrass and algae in Grande-Anse

While on SCUBA we found other interesting animals
like this tiny nudibranch in the invasive seagrass

By the end of the week in Grande-Anse, Martinique we completed 124 transects for a total of more than 75 km of swimming! Our seagrass surveys revealed that there is a great deal of damage to the seagrass beds caused primarily by anchors and abandoned fish traps which likely promote expansion of the invasive seagrass.

Left: Scar left by anchor chain in seagrass bed; Right: Abandoned fish trap surrounded by juvenile fish

For the second part of the trip, Elizabeth and Vincent moved on to Guadeloupe to continue the turtle and seagrass surveys in Malendure, a tourist beach in front of the Cousteau Marine Reserve. Here, the bay is much smaller than Grande-Anse but we are always impressed by the difference between the two sites. We see schools of adult fish in Malendure, whereas in Grande-Anse the fishes are mostly juveniles and scarce.

Flounder found in the shallow water of Malendure

On Guadeloupe, we received the help of the National Parc and Jeffrey Bernus who assisted us with our transect surveys every day. We also received help, in the form of field assistance, seagrass sample processing and advice, from the Réseau tortue de Guadeloupe, of Cap Naturel and Evasion Tropicale. With all of this help managed 469 turtle sightings across 126 transects for a total of 50.4 km snorkeled in just 5 days in Malendure!

After two intense but exciting weeks, we returned to Miami with our seagrass samples and a complete data set for analysis. We could not have done it without our local collaborators! Go team!

Sharks of Rangiroa

The lab's first trip to Rangiroa

For the past several years, the lab has been working on sharks and rays in French Polynesia using a variety of methods and tools, including drones and remote underwater cameras.  Our goal is to better understand the behavior of these animals on reefs and how they interact with other species. Ultimately, we want to figure out how important sharks are to the health of reefs.  Our work started on Moorea (you can read about our first trip in the October and November, 2013 blog posts) and expanded to Tetiaroa in collaboration with Dr. Aaron Wirsing at University of Washington.

Rangiroa is the world's second largest atoll.

At Blue Lagoon with Jeremy (center) and Eric (right).

This year, we have greatly expanded our work in French Polynesia.  Along with Dr. Eric Clua and CRIOBE we have started sampling multiple islands – both high islands and atolls – using baited remote underwater video systems (BRUVs).  This work will help us understand what drives patterns of shark abundance and the species inhabiting a particular island or reef type. The 1,000 camera drops (each 90-min long) that we plan to make are part of the Global FinPrint Project that will survey more than 400 reefs around the world!  PhD student Frances Farabaugh is leading the shark and ray analyses for the lab in French Polynesia.  Even though 1,000 drops and 1,500 hours of footage seems like a lot it is really just scratching the surface of French Polynesia, which covers a huge area of the Pacific Ocean! The more than 100 islands of French Polynesia are spread across about 2,000 miles!

Frances preparing to set BRUVs

In February, Jeremy Kiszka, Frances, and I made our first trip to Rangiroa to meet Eric to continue sampling for FinPrint and to begin other studies.  Rangiroa is found northwest of Moorea and Tahiti and is the world’s second largest atoll.  The lagoon in the middle of the atoll is about 70 km across from east to west and 40 km from north to south.  While Frances worked on FinPrint sampling, Jeremy, Eric and I started projects on nursery habitats of the lagoon and the movements and feeding behavior of bigger sharks on the reef that lines the outside of the atoll (the forereef). 

The blacktip reef shark nursery at Blue Lagoon

On our first day, we headed to Blue Lagoon – a small, shallow lagoon within the larger lagoon of the atoll.  Think of a (very small) hot tub in a (very large) swimming pool.  Pulling to the edge of Blue Lagoon on our first day, we were greeted by dozens of mostly full-grown blacktip reef sharks at the mooring.  Blacktip reef sharks can be found from the forereef to the lagoon and don’t get particularly big – only about 4-5 feet on average.  But we were interested in the younger sharks that call the shallow flats of Blue Lagoon home.  We hadn’t been there long before we were watching 20 small sharks – from newborns (about 1.5’ or 50 cm long) to animals that are around 3 years old.  For the youngest sharks, they need to stay in these shallow areas to stay safe from predators, particularly large lemon sharks that are found in the deeper waters of the lagoons.  We had a magnificent morning, capturing sharks and getting samples to help us learn where they are feeding and to get an idea of what their favorite foods might be.  Once we finished in the lagoon, we headed back to the mooring to test out a 360 degree dome camera system!  This system lets us see sharks all around the camera stand instead of just in one direction.  We are using the 360 cameras to get a better understanding of just how many sharks might be around when we do our standard counts for FinPrint that use one camera and to get a better view of their behavior.  PhD student Jimmy Kilfoil, who has been working in Tetiaroa, has been leading these studies but we took the opportunity to collect data since there were so many sharks around.  During the trial, we even had some big sicklefin lemon sharks show up.  With impressive predators like these just outside Blue Lagoon it is easy to see why the babies stick to the shallows!

Larger blacktip reef sharks outside Blue Lagoon

Sicklefin lemon shark

Another project that we worked on was to understand the movements and feeding behavior of the large shark species found on the forereef.  To do this, we captured and collected blood from gray reef sharks and silvertip sharks.  Because we didn’t want to catch great hammerhead sharks (they can be very sensitive), we got help from a professional free diver, Francis, who can hold his breath long enough to dive 60 meters!  The idea was for him to use a modified spear to take a small sample of skin.  The blood and skin samples help us understand where the different species might be feeding – in the lagoon, along the reef, or out in deeper water.  Knowing this might help us figure out how so many species are able to coexist!

Out in blue water off the reef, we waited by a baited canister for hammerheads.  We didn’t see any during my time there but Francis got several samples of silky sharks and tiger sharks!  One tiger shark was about 4m long! With any luck we will get those hammerhead samples eventually! We also were able to deploy a satellite tag on a silvertip shark which will help us determine its movements.  Silvertips are usually thought of as the largest resident sharks on reefs, but the satellite tag will tell us just how far the silvertip goes.  The tag will stay on the shark for three months and then pop off and float to the surface to download its data.  Hopefully, we will have results to share soon!

We couldn't have done it without the amazing people at the Rangiroa Diving Center!!

And Miki Miki Lodge

We saw bottlenose dolphins in the pass every day.