pregnant tiger shark

It’s finally happening! After over a year of corona-related delays the Pregnant Tiger Shark Expedition is finally underway. We just finished our very first day of tagging and, if I may say so, we started off with a bang. After a full day of tagging, we caught a total of 15 sharks: 14 reef sharks and one lucky (or unlucky, depending on your perspective) female tiger shark.

But, before we continue, let’s do some introductions. Over the next few days various expedition members will be writing some posts to update you on how the expedition is going, where we are, what we are doing, and what we hope to accomplish. I get the dubious honour of going first, so let’s set the bar high.

My name is Roxanne-Liana Francisca, but everyone calls me Rox. I work for STINAPA Bonaire as a Wildlife and Marine Biologist. For this expedition I will be one of the people ensuring that the data we are collecting is properly entered, tagged, and stored. Remember, it’s not science if you don’t write it down!

As the name of the expedition implies, we are heading to the Saba Bank to hopefully catch and tag some pregnant tiger sharks. Tiger sharks are a highly migratory species and have been known to cover vast distances. One of the sharks tagged in 2016 by the St. Maarten Nature Foundation, also joining on the expedition, was first tagged and released in St. Maarten and then picked up by the satellite tag all the way in Trinidad. Hopefully through this expedition, and the data we will gather, we will get a better idea of the migratory patterns of these sharks, and where they give birth, enabling us to better protect them.

Our team is made up of 20 people. This includes members of nature management organizations from 5 of the Dutch Caribbean islands. We have with us Aruba National Parks Foundation (FPNA), STINAPA Bonaire, Nature Foundation St. Maarten, St. Eustatius National Parks (STENAPA),the Saba Conservation Foundation (SCF), as well as representatives of the Dutch Caribbean Nature Alliance (DCNA), University of Groningen, Arizona State University, and World Wide Fund for Nature – The Netherlands(WWF-NL) who facilitated the necessary funds to realize this expedition.

Keep following us on DCNA’s website,  Facebook (Dutch Caribbean Nature Alliance), Instagram (dcnanature)  for daily updates!

Article published in the Special Edition BioNews: Tiger Shark Expedition

Hi everyone, my name is Giancarlo Nunes and I’m the Research and Conservation manager for Fundacion Parke Nacional Aruba. I can be considered a jack of all trades for this trip since I’ve been lucky enough to receive training on several of these expeditions. What I mostly do though is assist in getting the shark safely secured to the boat by either handling the head or the tail of the shark.

What is the proper way to restrain a shark for tagging?

Once a shark is hooked to the line, the line is then used to carefully guide the shark to the side of the boat with it’s head facing towards the front of the boat. Another crew member then secures the shark’s tail to the back end of the boat using a rope which is thick enough to hold the shark but also soft enough to not cut the shark’s skin. At this moment the shark is considered secured and the science team can start with data collection. During data collection it is important for the shark handler to continuously assess the shark’s health. One of the most important things during the expedition is to make sure the sharks are strong and healthy so they can be released with no issues.

How do you tag a shark?

Photo credit: Sami Kattan / Beneath the Waves

There are several types of tags being used on this expedition and each one serves a different purpose. All the tags are attached either on the shark’s fin or at the base of the fin. Shark fins are made out of cartilage which is the same material human ears are made of. Tagging a shark can be compared to piercing a person’s ear. The tags don’t affect the shark’s survival much like earrings don’t affect a person’s daily activities.

What type of tags are used?
There are many types of shark tags and each have a different purpose. For this expedition we will be using the following three types.
1. Floy tags are used as an external visual marker for researchers and fishermen to know if a shark as been tagged for research purposes. Floy tags are shaped like uncooked spaghetti which is why they are also called spaghetti tags. Floy tags contain contact information of the organization which tagged the sharks.
2. PIT tags are small chips which are inserted under the skin via a needle at the base of the fin and can not be removed as easily as a Floy tag. Each PIT tag has a unique code which can be read using a portable scanner.
PIT tagging a shark is comparable to chipping a pet animal for identification purposes.
3. Satellite tags are work via GPS and are attached to the top of the shark’s fin. A signal is sent to orbital satellites whenever a tagged shark’s fin breaches the water’s surface which allows us to track it’s location. Knowing where sharks go allow us to discover areas important to their survival such feeding and breeding habitats.

Keep following us on DCNA’s website,  Facebook (Dutch Caribbean Nature Alliance), Instagram (dcnanature)  for daily updates!

Article published in the Special Edition BioNews: Tiger Shark Expedition

My name is Francois Mille, I am a Marine Park Ranger at STENAPA in Sint Eustatius.

Sint Eustatius is a small volcanic island, 21km2, that belongs to the Dutch Kingdom. It was incorporated into the Netherlands in October 2010. There are about 3’500 souls living there. It is a dormant stratovolcano. The second highest mountain of the Netherlands.

Stenapa stands for St Eustatius National Park Foundation.  We manage 3 protected area and a botanical garden, which correspond to 33km2. Bigger than the island itself!

My role in the expedition involves various tasks. In the morning I hopped on the Queen Beatrix 2, the support boat. I also help placing the line in the water to catch the sharks, including baiting the hook and attaching the hook line to the main one. I really like this part because we must put the line close to each other, so you have no break in between.  At the end of the day, I prepare the equipment for the next day. They need a good rinsing because they do not like salt water. For that task I am helped by Leslie Hickerson, she is from Nature Foundation St. Maarten, so we have a good chat while doing this. Then I help whoever need helps!

But yesterday was great because I got to go on Lady Rebecca to help tag the biggest female Tiger shark, and that was great!

Tiger shark (Galeocerdo cuvier) © Daniel Norwood

Sometimes people ask me how we could help the shark population.

• First do not eat or buy any shark related product. Some country sells fins, meat, or liver oil from sharks.
• Second, use less plastic. We use too much plastic, a part ends up in the ocean, and animal eat them, by mistake, confusing them with prey. Or worse, they get entangled in trash and drown.
• Third, sharks have been on earth since before the first trees appeared. It is sad to think that humans are responsible for killing most of them. That humans are pushing some species to disappear completely. When humans catch sharks for their fins, they cut the fins from the sharks while they are alive and throw them back in the sea alive! Their death is horrible.

You might wonder why it is important to care about shark. If you have been watching Jaws, you might think we need to kill them all. But the reality is far from a Hollywood movie.

Sharks are very important because they are at the top of the food chain. Imagine a pyramid, they are on top, taking care of the large fish that are one step below them. Now, imagine no more sharks: those larger fish will not be hunted, therefore they will develop a lot, maybe a bit too much. Then one day those fishes would not get any food because they eat them all. So those will start to die as well. You will then end up with several steps of pyramid that would disappear completely. Before you know it, just like that all the fish are sick and dying, all the way to the plankton, and this can happen rapidly.

Sharks are important because as predator they will hunt the weak and the sick prey. They keep the marine ecosystem in balance.

A way to help shark is to create protected areas where you cannot harm them. The Yarari Marine Mammal and Shark Sanctuary was established by the Dutch government in 2015 to protect sharks in the Caribbean Netherlands.  This corresponds to the 3 following islands: Bonaire, Saba and Sint Eustatius. The purpose is to try to keep shark population steady as their numbers are on high decline.

You might be surprised but the more sharks there are, the more fish there will be.

Though we do not know everything about sharks, we do expeditions such as these. For example, we know that female tiger sharks cruise through the Saba Bank, but we do not know if they breed there.

And some fishermen with very large and long fish net catch shark by mistake. So it is important not to do that where sharks are protected.

It is important for those islands to protect the fish and it has an important economic impact.

But not only does the sanctuary protect sharks, but all the marine mammals in the area as there are dolphins and whales living there or just passing by during their migration.

Photos by: Daniel Norwood

Article included in Special Edition Bionews: Tiger Shark Expedition

Much of the lives of the most iconic shark species – including the tiger shark – remains a secret, even to shark researchers. This is because these large sharks are capable of migrating thousands of miles across oceans in a single year. One of the most unsolved mystery of sharks’ lives is where adult females go during their pregnancy. Discovering the habitats that are important during this life stage will be critical for creating conservation protections for mother sharks and their developing pups.

Tiger sharks are wide-ranging marine predators that can carry around 10-80 (yes, up to 80!) pups within their womb while pregnant. Finally, after about 15 months in the womb, the mother tiger shark will give birth to the live pups that are around 75 cm long. While we know this basic information about tiger shark reproduction, we have yet to uncover many of the breeding grounds, gestation grounds, and pupping grounds for this migratory species. Discovering this information will require the use of novel technologies, and that’s where our research comes into play.

My name is Brooke Anderson and I am a PhD student at Arizona State University studying sharks, their movements, and their movements relate to reproduction. I am lucky to be a part of this team of researchers trying to figure out if and how pregnant tiger sharks are using the Yarari Sanctuary and the wider Caribbean.

To help solve this mystery, we must first set out to the Saba Bank and do some fishing. Once we catch a large female tiger shark, we will secure her along the research vessel and take several size measurements to confirm that she is healthy and mature. Female tiger sharks mature at a whopping 3 meters in length! We can also examine her for fresh bite marks on her fins or body, which indicates that she had recently mated and could be pregnant.

After we collect this information on her maturity, we will rotate her upside down in the water to initiate tonic immobility. Tonic immobility is a natural reflex in sharks that induces a trance-like state of inactivity. This trance-like state help keeps the shark calm and still for the next part of the workup where my expertise comes into play. I will be able to use a portable ultrasound (from E.I. Medical Imaging) – just like we could use on a human – to get a look inside the shark’s womb for hidden pups. If she is pregnant, we will see on the ultrasound many miniature tiger sharks inside their mother’s womb! We can even use the ultrasound to take measurements and determine the size of the pups – this helps us to estimate how far along in her pregnancy that the mother tiger shark is.

Image of a tiger shark embryo as seen on the portable ultrasound.

Next, we can attach a satellite tag to the mother tiger shark to track where she goes throughout her pregnancy in near real time. This will allow us to determine the extent that the Yarari Sanctuary, Saba Bank, and the surrounding eastern Caribbean are used as important habitats for pregnant tiger sharks for the very first time. With this information, we can help assess the effectiveness of current conservation and management strategies for this near-threatened and ecologically important species. Stay tuned to see if we were able to find pregnant tiger sharks and where they might be headed on their journey to motherhood.

Keep following us on DCNA’s website,  Facebook (Dutch Caribbean Nature Alliance), Instagram (dcnanature)  for updates about the Pregnant Tiger Shark Expedition!

Article included in the Special Edition BioNews: Tiger Shark Expedition

The Dutch Caribbean waters are home to more than thirty species of sharks and rays. With the creation of the Yarari Marine Mammal and Shark Sanctuary in 2015, these species have received increased attention and protection.  The intention of this sanctuary was to create a network of protected habitats stretching across the Caribbean.  Currently this sanctuary includes the waters around the islands of Saba, St. Eustatius and Bonaire.

Saba Bank

A recent expedition to the Saba Bank focused on learning more about tiger sharks and how they use this habitat.  Saba Bank, located 11 kilometers from Saba, is a submerged atoll world renown for its rich biodiversity.  This seamount rises 1800 meters from the sea floor and is topped with over 100 square kilometers of coral reef. This area is the largest national park within the Kingdom of the Netherlands.

The Expedition

Photo credit © Daniel Norwood (all rights reserved)

The Tiger Shark Expedition was the first of its kind for the Saba Bank.  During this project five satellite tags were attached and researchers confirmed the pregnancy stages via ultrasound for two different species of sharks.  In total, 56 sharks, including 16 tiger sharks, were identified.

This project was a collaborative effort by the Protected Area Management Organizations of the Dutch Caribbean: Saba Conservation Foundation (SCF), Nature Foundation St. Maarten (NFSXM), St. Eustatius National Parks (STENAPA), STINAPA Bonaire, the Aruba National Parks Foundation (FPNA), the Dutch Caribbean Nature Alliance (DCNA) and World Wildlife Fund for Nature- The Netherlands (WWF-NL), Arizona State University, University of Groningen, Beneath the Waves and funded by the Biodiversity Fund of the World Wildlife Fund for Nature- The Netherlands (WWF-NL) and Dutch Postcode Lottery.

Photo credit © Daniel Norwood (all rights reserved)

This special edition BioNews is the culmination of these efforts.  Understanding the shark species that utilize the Dutch Caribbean waters is crucial step in improving conservation measures moving forward.

• Unraveling the Mysteries of the Saba Bank: DCNA Tiger Shark Expedition 2021
• Tiger Sharks and the Saba Bank
• Uncovering the mystery of tiger shark reproduction in the eastern Caribbean
• The value of sharks
• Shark handling techniques
• Prenant Tiger Shark Expedition 2021 is well underway!
• Expedition on the Saba Bank to Enhance Tiger Shark Protection
• Reef sharks move to deeper water as they mature
   

The full special edition can be found here: https://dcnanature.org/tiger-shark/