The Safina Center

May 6th
2014

Shark Tagging, Bahamas – Part 2

Blue Ocean Institute Fellow Dr. Demian Chapman, is leading a scientific research expedition in the Bahamian Shark Sanctuary. Chapman’s team is conducting groundbreaking research on the movements and behavior patterns of different shark species in an attempt to better understand and protect them.

Christine O’Connell, a science communicator at the Alan Alda Center for Communicating Science at Stony Brook University, is part of Chapman’s team and is blogging about their experiences from the Bahamas.

Read on and stay tuned for dispatches from the field!

WHEN AT FIRST YOU DON’T SUCCEED

April 22, 2014, by Christine O’Connell

We drove the big boat south today toward the island of Andros. The winds were up and the sea was choppy. As a marine scientist who focuses much of her time on science communication these days, it’s nice to get a chance to go back out in the field. It’s great to be working on a project that involves cutting edge science that has real management implications for the protection of endangered and threatened shark species throughout the Caribbean.

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Why sharks?

Sharks sit atop the ocean’s food chain and play critical roles in sustaining healthy and balanced ocean environments. However, even these apex predators are vulnerable to human activities and are in peril throughout most of the world’s oceans. Sharks have been severely overfished, largely as a result of increasing demand for shark fin soup, a popular luxury dish in Asia that can fetch upwards of $100 per bowl.

Shark conservation efforts face many challenges. Sharks are slow to reach sexual maturity, and are extremely vulnerable to overfishing. They produce relatively few offspring, and, even with strict protections, face long population recovery times.

Areas designated as ‘shark sanctuaries’, such as the Bahamas, provide sharks with protection from overfishing, and therefore allow shark populations an opportunity to recover. However, these sanctuaries will only be effective if sharks stay within sanctuary borders long enough to reproduce. Dr. Chapman’s research team is mapping critical juvenile shark habitats and nursery sites around the Bahamas and tracking behavior patterns of adult sharks. Once compiled, this information will be shared with the Bahamian government, so that additional protections can be provided to shark populations. If the Bahamian shark sanctuary is shown to be successful, it will serve as a model for other areas in the Caribbean.


Today we left the mangrove nursery grounds of the lemon sharks, and headed out to sea toward an old navel buoy. Fish like to hang out near old buoys – they provide a bit of cover out there in the big ocean. And, where little fish like to hang out, you find big fish. We were looking for a very big fish – a silky shark, Carcharhinus falciformus. Unfortunately, we got there a bit late in the day and didn’t catch anything. We’ll try again tomorrow.

Later in the day, we pulled up to the marina in Fresh Creek, Andros – our home for the night. There were some fishermen cleaning the day’s catch on the dock. Mark went to have a look thinking there might be some sharks around. There was. A big blacktip shark was circling. Blacktips, Carcharhinus limbatus, are a common coastal species of shark found worldwide that like to hang out near reefs and marinas. Blacktips are fast swimming sharks that can leap out of the water, making them popular catches among recreational fishermen.

Jerry pulling the shark in with his bare hands and some fishing line.

Jerry pulling the shark in with his bare hands and some fishing line.

Seeing our excitement, Jerry, a middle-aged Bahamian fisherman who was the dock master, threw a line into the water. The shark bit. It was amazing – watching him pull this shark in with his bare hands! No reel, no rod, just line in hand. It fought and flipped out of the water, but he didn’t let up. Mark grabbed the science kit and we ran over to get some measurements. We hopped into a little boat tied up on the dock as Jerry and Sean guided the shark along the boat’s side. Sean and Mark took a DNA sample and I wrote down the measurements…195 cm – that is over 6 feet long! Sean said it was one of the biggest blacktips he had ever seen.

Sean leading in the shark for measurements.

Sean leading in the shark for measurements.

We tagged the shark and sent in on its way. A good end to the day.

Mark releasing the shark after we tagged it.

Mark releasing the shark after we tagged it.

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WAITING

April 23, 2014, Christine O’Connell

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Today we headed to a different naval buoy to try our luck with the silky sharks again. Silky sharks are a deep-water species that, like the oceanic whitetip, have been severely overfished for their fins and suffered huge population declines from long-line fisheries. There are not many studies on silkies and we don’t know their migration patterns. The research team hopes to fit silkies with satellite tags to learn more about this elusive shark, including how far they dive down to hunt and where they move. According to Mark, the diving profiles are especially interesting. For sharks, the real data is in how it moves, not where it moves. If sharks are hunting at the same depth as fishing lines, they will likely be caught. Understanding where sharks spend their time is crucial for successful management.

We spent the good part of the morning at the buoy, but didn’t get any bites. It was empty – no sign of marine life other than sea birds. After heading to some fishing sites, we tried another pass at the buoy later in the day. The silkies were still eluding us. Buoys are usually good spots for sharks, but not this time. Later, we found out that this buoy had been removed from the ocean for repairs and just got put back last week. The fish had not re-colonized it yet.

Sometimes science isn’t easy. You can have solid methods, background research, the best-laid plans, and do everything right, but when you are dealing with living things (especially sharks), you can’t always count on them to cooperate…or in our case, bite. It can be really frustrating, but also extremely rewarding. You have to be persistent and take what you can from the situation. Even in failed science is discovery.

Setting the lines at the buoy.

Setting the lines at the buoy.

I also got to try my hand at fishing today, which was a lot of fun. Collecting fish samples is another part of the research expedition. The team wants to study what oceanic whitetips are eating and their place in the food web. By taking samples from a bunch of different fish found in the area, they can use stable isotope analysis for carbon and nitrogen and see where the fish fit in the food web.

Fishing takes lots of patience. Sitting there quietly, waiting, dropping the bait down to the bottom, reeling it up a bit, waiting, feeling a nibble, ready to pull the tip of my rod up…then nothing. More waiting. But always cautiously alert. Then a tug, and this time a bite. I quickly began to reel the fish in at the other end. It was a yellow-eyed rockfish, affectionately called for their big yellow eyes and pinky orange skin.

Christine reeling in a yellow-eyed rockfish.

Christine reeling in a yellow-eyed rockfish.

At the end of the day we caught 6 yellow-eyed rockfish, a small Spanish mackerel and a rockhind, which was brown with strawberry pink spots. We also caught a Nassau grouper – a brown and olive striped fish. As Joey was reeling it in, a huge cubera snapper grabbed it and took a big chunk out of its back! We watched the whole attack from above.

When we got back to the dock, we took some measurements and muscle samples. The rest got cooked up for dinner.

Mark taking measurements and muscle samples.

Mark taking measurements and muscle samples.

 

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Posted in:   Research, Sharks

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