Tag: dermal denticles

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Jennifer Goldner: Still Learning! August 22, 2011

NOAA Teacher at Sea
Jennifer Goldner
Aboard NOAA Ship Oregon II (NOAA Ship Tracker)
August 11 — August 24, 2011

Mission: Shark Longline Survey
Geographical Area: Southern Atlantic/Gulf of Mexico
Date: August 22, 2011

Weather Data from the Bridge
Latitude: 27.56 N
Longitude: 83.73 W
Wind Speed: 5.95 kts
Surface Water Temperature: 30.50 C
Air Temperature: 31.60 C
Relative Humidity: 66.00%

Science and Technology Log

Okay, so I admit, I can’t learn enough.  I just THOUGHT I was doing my last post, but I have to share with you some more information I learned toward the end of our journey.  So if you want to learn some “cool facts,” today’s post is for you!

Cool Fact #1:  Sargassum– This is a type of seaweed we saw in the ocean today alongside the ship.  It mats together in large clumps and serves as a refuge for larval fish.  It also is a type of “floating community” with lots of fish, such as mahi mahi, congregating around it.  Newly hatched sea turtles find refuge in sargassum.

Sargassum off the starboard side of NOAA Ship Oregon II
Sargassum off the starboard side of NOAA Ship Oregon II
Sargassum- courtesy of bing images
Sargassum- courtesy of bing images
sargassum fish
Sargassum fish

Cool Fact #2:  Shark skin samples and fin clips — All week long I have seen shark skin samples and fin clips taken, but today I found out from two of the scientists on our survey, Dr. Trey Driggers and Adam Pollack, what is done with these.  The skin sample is done so the shark can be identified down to the species.  For example, there are 3 species of smooth dogfish in the Gulf of Mexico.  They all look the same externally.  Keep in mind, the smooth dogfish shares the same genus (Mustelus), but the species differs.  One of the ways to tell them apart is to look at their skin sample under a microscope.  For this reason, every shark that is caught has a small sample of skin taken that is placed in alcohol for preservation.

Fin clip
Fin clip

When it gets to the lab, the scientist looks at the dermal denticles (scales) under a microscope.  If the denticle has 1 point, its species is either canis (common name– smooth dogfish) or norrisi (common name–Florida smooth dogfish).  If it has 3 points, its species is sinusmexicanus (common name- Gulf smooth dogfish).

The fin clip is collected and archived and later a DNA analysis is performed.  They are compared to fish of the Gulf of Mexico to tell if they are genetically different or similar.  This information is used for stock management.

Cool Fact #3: Otoliths– I have been assisting the scientists this week in getting the otoliths from various fish, such as red grouper, yellowedge grouper, and blueline tilefish.  Today I got to take the otoliths out myself.  By “myself,” I mean with the help of skilled scientist, Adam!    It was neat!  So what are otoliths?  They are the ear bones of fish.  They tell the age of the fish, much like the annual rings of a tree trunk do.   These are collected and put in an envelope with the identification number in order to be observed under a microscope in the lab.

Removing the otoliths- Thanks to Adam, Scientist, for teaching me how to do this!
Removing the otoliths- Thanks to Adam, Scientist, for teaching me how to do this!
Otoliths, courtesy of Google images
Otoliths, courtesy of Google images
Otoliths removed
Otoliths removed

Personal Log

Last night after our shift ended at midnight, by the light of the moon we watched a pod of about 25 dolphins chase flying fish and play in the wake of the boat.  I sure will miss all the sights the sea has to offer.  I will especially miss the people.

I mentioned in an earlier post that NOAA Ship Oregon II is like a city.  It has everything needed on board to run smoothly.  There are people with numerous kinds of backgrounds. Each and every one of these individuals is needed in order to successfully complete a NOAA mission, whatever it may be.

So now I’m talking to you kids.  Have you ever thought about what you want to be or do when you grow up?  How about starting now?  How about you adults, have you ever thought about trying to do something new and exciting?   I have a question for you (and I would like for you to put your answer in the poll):  If you could choose any job on this ship, what would it be?

If you will notice from my posts, I did not just cover the science end of this ship.  There are so many other careers going on to make these surveys work.  It’s a team effort.  Under the leadership of Cap Nelson, that’s exactly what you have here on NOAA Ship, Oregon II: a team effort.  And that’s what makes this ship a model for any team to follow.

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Maureen Anderson: Homeward Bound, August 7, 2011 (Post # 6)

 NOAA Teacher at Sea
Maureen Anderson
Aboard NOAA Ship Oregon II (NOAA Ship Tracker)
July 25 — August 9, 2011

Mission: Shark Longline Survey
Geographical Area: Southern Atlantic/Gulf of Mexico
Date: Sunday, August 7, 2011

Weather Data from the Bridge
Latitude: 34.22 N
Longitude: -077.05 W
Wind Speed: 16.38 kts
Surface Water Temperature: 28.10 C
Air Temperature: 28.90 C
Relative Humidity: 82%
Barometric Pressure: 1010.80 mb

Science and Technology Log

Last night, we finished up our last station.  In total, we had 761 catches for the whole survey across a dozen different species.  The sharks we caught ranged from small (less than 1 kilogram) to very large (134 kilograms).  For the very small sharks, I could sometimes see the spot where the umbilical cord was attached.

Over the last few days, I learned about shark reproduction. Sharks produce “pups” (baby sharks) through three different ways. One way is the pup develops in a placenta and is nourished by the mother.  It is then born live  (called viviparity).  A second way is an egg is produced and hatches inside the mother but there is no placental connection.  The embryo eats the yoke in the yoke sac until it is completely absorbed.  The pup is then born free-swimming.  (called ovoviviparity).  The third way is the mother lays a fertilized egg in the water and the pup is born externally (oviparity). The species we saw the most, the Atlantic sharpnose of the family Carcharhinus, produce pups through viviparity. For some species like the sandtiger shark, one of the pups will eat the other eggs inside the womb for nourishment and then just that one pup will be born.  Talk about survival of the fittest!

I was able to see what a shark embryo looks like. Ian Davenport, an evolutionary biologist from Xavier University of Louisiana is studying developmental biology in female sharks.  Ian is on the day shift with me and he was able to show me embryos from a pregnant female.  The mother was not alive when we caught her, so we made use of the body as much as possible for scientific purposes.

atlantic sharpnose embryo
This is an Atlantic sharpnose embryo. You can see the formation of eyes, snout, and tail. It is attached to a yoke sac.

You might be wondering how we can tell the difference between a male and a female shark. This is done through visual inspection. We look for the presence of “claspers” on a male shark.  A clasper is a male anatomical structure.  Males have two claspers.  If there are no claspers, it’s a female.

male with claspers
This is a male shark. There are two claspers alongside the pelvic fins.

female sharpnose

I experienced “shark burn” for the first time while handling an Atlantic Sharpnose the other day. I didn’t feel anything at first, but while I was taking measurements on its length, its tail rubbed me the wrong way. A few hours later, I noticed what felt like a stinging rash on my arm. Sharks have unique skin made of modified teeth called dermal denticles. These scales point towards the tail and help the shark swim quickly and efficiently. When you rub a shark from head to tail, it feels silky. If you rub it in the opposite direction, it feels like sandpaper. I learned this lesson the hard way!

dermal denticles magnified
This is shark skin magnified. These dermal denticles are sharp structures. From Google Images.

Species Seen:
Tiger Shark
Sandbar Shark
Atlantic Sharpnose Shark
Red Grouper
School of Dolphin Fish

tiger shark
Tiger shark. You can identify this shark by the markings on its body.

Personal Log

My team had a great sighting of a large hammerhead recently. It was about 10 feet long. We tried to use a tagging pole from the side of the boat instead of using the cradle but the hammerhead was so strong, it broke right off the line. Even though we couldn’t collect data, it was still exciting to see such a massive shark and get an idea of its power.

Last night we finished our final station and we are heading back to port in Charleston, SC. It was really great to work with such amazing people, not only on my shift, but everyone aboard the Oregon II. I came across a variety of people with interesting careers and backgrounds. Even though the work was sometimes physically demanding, it was informative and engaging the entire time. Thanks to NOAA for giving me the opportunity to participate in the Teacher at Sea program. I learned so much that I plan on bringing back to my students! A big thanks to Mark Grace, our chief scientist, for answering many of my questions, providing feedback, and showing me how to do many tasks. I also want to thank the day team for helping me learn so much – Amy, Heather, Jim, Ian, Cliff, Jeff, Mike, and our XO Jason for giving me feedback on my blog.  Thanks to Paul and Walter the amazing cooks.   To the entire crew of the Oregon II – thank you!  I had a great experience!

sunset
Sunset from the stern.