NOAA Teacher at Sea
Onboard NOAA Ship Oregon II
July 27 – August 8, 2012
Mission: Longline Shark Survey
Geographic area of cruise: Gulf of Mexico and Atlantic off the coast of Florida
Date: August 7, 2012
Weather Data From the Bridge:
Air Temperature (degrees C): 28.4
Wind Speed (knots): 8.62
Wind Direction (degree): 183
Relative Humidity (percent): 080
Barometric Pressure (millibars): 1015.41
Water Depth (meters): 43.4
Salinity (PSU): 35.660
Loose Ends at Sea
We are getting close to wrapping up this first leg of a four-leg survey. Speaking of wrapping things up, one very important skill you must know when on a ship is how to tie a knot. Not just any knot, but the right knot for the job, or things might not turn out. Got it?
There are three knots, which we used every day. The Blood Knot (sometimes called the Surgeon’s Knot), the Double Overhand Loop (sometimes called a Surgeon’s End Loop), and the Locking Half-Hitch on a Cleat.
The blood knot is used to tie two ropes together. When we return a longline, it has to be tied back on to the main spool. Watch Tim and Chris demonstrate how to tie this knot.
The double overhand loop is used, as the name implies, to put a loop on the end of a line. It is used at each end of the longline to secure the highflier.
The locking half hitch knot is tied on to a ship’s cleat in order to secure the mainline after it has been sent out. This gives us the opportunity to tie a double overhand loop on to the end in order to clip on the highflier.
We have also been seeing some more different animals during the past couple of days. We saw a green sea turtle surface twice. The first time was right in front of us on the starboard side of the ship. The second time was several minutes later at the stern. Just when I thought I would not get a picture of a dolphin, a trio of Atlantic spotted dolphins followed along the Oregon II as we let out the longline. Dolphins and all sea turtles are protected.
We have also been catching more sharks. Again, the most common species caught has been the sharpnose shark. We finally caught a silky shark, Carcharhinus falciformes on our shift. The ridge that runs along their back and the smooth, silky look to their skin can be used to identify them.
A 93.6 kilogram nurse shark, Ginglymostoma cirratum was caught and brought up using the cradle. These are bottom-feeding sharks and have an unusual texture to their skin. It feels like a basketball!
It is always nice when you witness the rare or unusual. Such was the case with the next shark we caught. Many photographs were taken in order to document this rare occurrence. After releasing the shark, it was identified as a Caribbean reef shark, Carcharhinus perezi. Mark Grace, who started this survey 18 years ago, believes this is only the third Caribbean reef shark ever caught on the longline survey! Rare indeed! Unbelievable–the very next longline we caught a second Caribbean reef shark!
Another first for the first leg of the 300th mission was a dusky shark, Carcharhinus obscurus. This is another rare shark to be found. This one was even bigger than the nurse shark weighing in at 107.3 kilograms! We keep the larger sharks in the cradle while data is collected before releasing them.
While cleaning up, this little remora was found on the deck. It is easy to see the suction disc on the top of its head. This is used to hold onto a larger fish and tag along for the ride, cleaning up bits of food missing the mouth of the host fish.
This amazing journey is winding down and coming to an end. I would be remiss not to thank the crew and scientists of the Oregon II. Their hospitality, professionalism, friendly dispositions, and patience (LOTS of patience) have made me feel more than welcome. They have made me feel as though, for a brief moment, I was a part of the team. Thank you and may the next 300 missions be as safe and successful as the first 300.