Mission: Shark Longline Survey
Geographical Area: Southern Atlantic/Gulf of Mexico
Date: Tuesday, July 28, 2011
Weather Data from the Bridge
Latitude: 27.34 N
Longitude: -080.03 W
Speed: 1.50 kts
Wind Speed: 12.19 kts
Wind Direction: 140.99
Surface Water Temperature: 27.40 C
Surface Water Salinity: 24.04 PSU
Air Temperature: 29.50 C
Relative Humidity: 72%
Barometric Pressure: 1018.06 mb
Science and Technology Log
Today we arrived at our first station. It took us a while (3 days) to get here. Where is here? We are off the eastern coast of Florida right now.
You might be wondering… how do you catch a shark? In order to collect data on sharks, the ship slowed down so that we could set bait and begin to fish. The bait was big chunks of mackerel placed onto hooks. (Mackerel is just one of many fish sharks enjoy eating). Then we attached a tag (with an identification number) to each hook and released it from the stern (back) of the ship. All together, there were 100 baited hooks on a monofilament line that was 1 nautical mile long (equal to 1.15 miles). The baited hooks were released every 60 feet. Then we waited one hour before hauling in the line. This kind of work takes teamwork – one person to get the tag ready, one person to attach the tag to the baited hook, and one person to make sure the line is going out steadily. There is also one person collecting data on a laptop about the tag number that went out. Pretty much, the job can’t be done without people working together.
One hour later, we began to haul in the line. Out of 100 hooks, we caught 4 sharks. There was one Atlantic sharpnose and three hammerheads. If the shark was small enough, we brought it aboard the deck to take measurements. If it was too large to bring in by hand, we used a cradle, which is basically a net with a strong frame that sits off the side of the boat. We measured the length in millimeters using a measuring board, mass in kilograms using a spring scale, gender (using our eyes), and took a tiny sample of the dorsal fin tissue (which helps with DNA identification). All of this is done within minutes. The shark data is collected very quickly so that we can get it back into the water as soon as possible.
At our second station today, we caught many Atlantic Sharpnose and one Goliath Grouper. The grouper was enormous – 300 pounds! (as you can see in the picture below). We also tagged a shark using something called a Roto-tag. This small yellow device is attached to the middle of the dorsal fin and has identification information and a phone number to call if the shark is found. The shark was also injected with an antibiotic. It is deposited in the vertebrae as a fluorescent marker. The number of growth rings deposited in the vertebrae after the marker help scientists determine the shark’s age. Kind of like rings on a tree trunk.
Try your luck with this math problem (keep your summer math rust-free!):
We cut up one whole mackerel into 4 pieces and place each piece on a hook. There are 100 hooks. We set out a line of 100 hooks 5 times a day. We do this repeatedly for 13 days.
At first I was a little hesitant to handle the sharks while they were on deck. But under the tutelage of our chief scientist, Mark Grace, I began to feel more confident (thanks Mark!) He showed me how to hold the shark by the tail while also holding the mouth closed. Once I got the hang of it, I really enjoyed it. After collecting data, I was able to release a few sharks back into the water and watch them swim away.
I had a hard time sleeping well last night because yesterday I took a 3 hour nap during the day to try to calm my stomach. But since my shift ends at midnight tonight, I’m sure I’ll fall asleep no problem.
I have been eating wonderful food cooked by our talented stewards (chefs). Some of our meals have included beef tenderloin, burgers, pork chops, biscuits, mashed potatoes…the list goes on (yes, there are some vegetables in there too!). Meal times are only scheduled for one hour, so if you know you will miss your meal due to a shift you can request that a plate be set aside for you. Of course there is unlimited cereal, snacks, sandwiches…and ice cream!
Now it’s off to bed after a long shift ending at midnight.
Species Seen Today:
Atlantic Sharpnose Shark
Scalloped Hammerhead Shark