h 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.
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.
We tagged the shark and sent in on its way. A good end to the day.
April 23, 2014, Christine O’Connell
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.
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 diffe