hammerhead sharks – NOAA Teacher at Sea Blog

August 5, 2015August 21, 2021

Kathleen Gibson, Hammerheads on the Line, August 4, 2015

NOAA Teacher at Sea
Kathleen Gibson
Aboard NOAA Ship Oregon II
July 25 – August 8, 2015

Mission: Shark Longline Survey
Geographic Area of the Cruise: Atlantic Ocean off the Florida and Carolina Coast
Date: Aug 4, 2015

Coordinates:
LAT 3323.870N
LONG 07736.658 W

Great Hammerhead Photo Credit: Ian Davenport — Great Hammerhead (Photo Credit: Ian Davenport)

Weather Data from the Bridge:
Wind speed (knots): 28
Sea Temp (deg C): 29.2
Air Temp (deg C): 24.2

Early this morning the night shift caught and cradled a great hammerhead shark (Sphyrna mokarran). This is a first for this cruise leg. I’m sure that just saying “Hammerhead” conjures an image of a shark with an unusual head projection (cephalofoil), but did you know that there are at least 8 distinct Hammerhead species? Thus far in the cruise we have caught 4 scalloped hammerheads (Sphyrna lewini), one of which I was fortunate to tag.

Science and Technology Log

All eight species of hammerhead sharks have cephalofoils with differences noted in shape, size, and eye placement, to name a few. Research indicates that this structure acts as a hydrofoil or rudder, increasing the shark’s agility. In addition, the structure contains a high concentration of specialized electro sensory organs (Ampullae of Lorenzini) that help the shark detect electric signals of other organisms nearby. The eye placement at each end of the cephalofoil allows hammerhead sharks to have essentially a panoramic view with only a slight movement of their head – quite handy when hunting or avoiding other predators.

Comparison of Scalloped and Great Hammerhead Sharks
Image Credit: NOAA Fisheries Shark Species

Great hammerhead sharks are highly migratory. They are found worldwide in tropical latitudes, and at various depths. There are no geographically Distinct Population Segments (DPS) identified. The great hammerhead, as its name implies, is the largest of the group and average size estimates of mature individuals varies between 10-14 ft in length with a weight approximately 500 lb.; the largest recorded was 20 ft in length. The one we caught was ll ft. in length.

As with most shark species, the numbers declined rapidly between 1975 and 1995 due to the fin fishing industry and focused sport fishing often fueled by fear and misinformation. One has to wonder what the average length was before that time.

Scalloped Hammerhead sharks are the most common hammerhead species. Their habitat overlaps that of the great hammerhead, though they are more often found in slightly shallower waters. In contrast to the great hammerhead, scalloped hammerheads are only semi-migratory, and scientists have identified Distinct Population Segments around the world. This is important information when evaluating population size and determining which groups, if any, need regulatory protection.

Weighing a small Scalloped Hammerhead Photo Credit: Ken Wilkinson — *Weighing a small scalloped hammerhead*
Photo Credit: Ken Wilkinson

Scalloped Hammerhead on deck. Photo: Erica Nuss — *Scalloped hammerhead on deck*
Photo: Ian Davenport

The average life expectancy for both species is approximately 30 years. Males tend to become sexually mature before females, at smaller weights; females mature between 7-10 years (sources vary). In my last log I discussed shark reproduction – Oviparous vs. Viviparous. (egg laying vs. live birth). All hammerheads are viviparous placental sharks but reproductive patterns do differ. Great hammerheads bear young every two years, typically having 20-40 pups. A great hammerhead recently caught by a fisherman in Florida was found to be pregnant with 33 pups. Scalloped have slightly fewer pups in each brood, but can reproduce more frequently.

Career Spotlight – NOAA Corps

Setting and retrieving the Longline requires coordination between Deck Operations and the Bridge. Up until now I’ve highlighted those on deck. Let’s learn a bit about two NOAA officers on the Bridge.

The NOAA Corps is one of the 7 Uniformed Services of the United States and all members are officers. The Corps’ charge is to support the scientific mission of NOAA, operating and navigating NOAA ships and airplanes. Applicants for the Corps must have earned Bachelor’s degree and many have graduate degrees. A science degree is not required but a significant number of science units must have been completed. It’s not unusual for Corps recruits to have done post-baccalaureate studies to complete the required science coursework. New recruits go through Basic Officer’s Training at the Coast Guard Academy in New London, Connecticut.

Lt. Lecia Salerno – Executive Officer (XO) – NOAA

: Lt. Lecia Salerno at the helm or the Oregon II during Longline retrieval.

Lt. Salerno is a 10-year veteran of the NOAA Corps and has significant experience with ship operations. She was recently assigned to the Oregon II as the XO. This is Lecia’s first assignment as an XO and she reports directly to Captain Dave Nelson. In addition to her Bridge responsibilities, she manages personnel issues, ship accounts and expenditures. During these first few weeks on her new ship, Lt. Salerno is on watch for split shifts – day and night – and is quickly becoming familiar with the nuances of the Oregon II. This ship is the oldest (and much loved) ship in NOAA’s fleet, having been built in 1964, which can make it a challenge to pilot. It’s no small task to maneuver a 170-foot vessel up to a small highflyer and a float, and continue moving the ship along the Longline throughout retrieval.

Lecia has a strong academic background in science and in the liberal arts and initially considered joining another branch of the military after college. Her assignments with NOAA incorporate her varied interests and expertise, which she feels makes her job that much more rewarding.

Lt. Laura Dwyer on the Bridge of the Oregon II — Lt. Laura Dwyer on the Bridge of the *Oregon II*

Lt. Laura Dwyer- Junior Officer – NOAA Corps

Laura has always had a love for the ocean, but did not initially look in that direction for a career. She first earned a degree in International Business from James Madison University. Her interest in marine life took her back to the sea and she spent a number of years as a scuba diving instructor in the U.S. and Australia. Laura returned to the U.S. to take additional biology coursework. During that time she more fully investigated the NOAA Corps, applied and was accepted.

Laura has been on the Oregon II for 1.5 years and loves her work. When she is on shift she independently handles the ship during all operations and also acts as Navigator. What she loves about the Corps is that the work merges science and technology, and there are many opportunities for her to grow professionally. In December Laura will be assigned to a shore duty unit that is developing Unmanned Underwater Vehicles (UUV).

Personal Log

Measuring a Sharpnose Photo: Kristin Hannan — *Notice the white spots on the dorsal side of this atlantic sharpnose, characteristic of this species.*
Photo: Kristin Hannan

It’s amazing to think that just over a week ago I held my first live shark. We caught over 30 sharks at our first station and our inexperience showed. At first even the small ones looked like all teeth and tail, and those teeth are not only sharp but carry some pretty nasty bacteria. It took all of us (new volunteers) forever to get the hooks out quickly without causing significant trauma to the shark–or ourselves. A tail smack from this small-but-mighty tiger shark pictured below left me with a wedge-shaped bruise for a week!

Immature Male Tiger Shark. He's cute but he taught me a lesson with his tail. — *Immature Male Tiger Shark.*
*He’s cute but he taught me a lesson with his tail.*

Since then we have caught hundreds of sharks. We’ve caught so many Atlantic Sharpnose that on occasion it seems mundane. Then I catch myself and realize how amazing it is to be doing what I’m doing– holding a wild animal in my hands, freeing it from the circle hook (finally!), looking at the detailed pattern of its skin, and feeling it’s rough texture, measuring it and releasing it back into the sea.

Sandbar Shark on the Line — *A beautiful sandbar shark on the line.*

I’m pleased to be able to say that my day shift team has become much more confident and efficient. Our mid-day haul yesterday numbered over 40 sharks, including a few large sharks that were cradled, and it went really smoothly.

Weighing in. Hook out - No Problem! Photo: Jim Nienow — *An Atlantic Sharpnose weighing in at 2.1 kg.*
Photo: Kristin Hannan

Out it Comes - No Problem Photo: Ian Davenport — *Taking a closer look at an Atlantic Sharpnose shark.*
Photo: Ian Davenport

At this point I’ve had a chance to work at most of the volunteer stations including baiting hooks, throwing off the high-flyer marker, numbering, gangions, throwing bait, data entry, tagging shark, removing hooks, and measuring/ weighing. A highlight of last night was getting to throw out the hook to pull in the high-flyer marker at the start of retrieval. I’m not known for having the best throwing arm but it all worked out!

Ready to Throw Photo: Kristin Hannan — *Ready to Throw*
Photo: Kristin Hannan

Got it! Photo: Kristin Hannan — *Right on Target!*
Photo: Kristin Hannan

Question of the Day: What is this?

NOAA SHARK FACTS: Bite off More that you can chew

For more on hammerheads: click

For my incoming Marine Science students — Investigate two other hammerhead species. How are they distinguished from great hammerheads?

July 30, 2015August 21, 2021

Kathleen Gibson, Time to Fish! July 29, 2015

High flyer away! Photo Credit : Kristin Hannan — High flyer away!
Photo Credit : Kristin Hannan

NOAA Teacher at Sea
Kathleen Gibson
Aboard NOAA Ship Oregon II
July 25-August 8, 2015

Mission: Shark Longline Survey
Geographic Area of the Cruise: Atlantic Ocean off the Florida and Carolina Coast
Date: July 29, 2015
Coordinates:
LAT 2933.3326N
LONG 8029.065W

Weather Data from the Bridge:
Wind speed (knots): 9.2
Sea Temp (deg C): 29.6
Air Temp (deg C): 28.7

Yesterday was the first full day of sampling. We were off the coast of Miami, FL and it was relatively shallow. I’m not sure how many sharks I expected to see on my first day, but certainly not the 80 + that we did catch!

Science and Technology Log – A, B, C’s of Fishing for Sharks

Kristin Hannan preselected our stations following a random stratified approach. Sampling stations have A, B, or C designations, depending on the depth (A is more shallow than B or C). The night crew went on duty at midnight and completed one station yesterday morning. We completed three stations during our shift yesterday and three more today.

The bridge lets us know when we’re 30 minutes from our station, and we begin preparations. We bait the hooks with mackerel 20 minutes ahead of time.

When we get to the station, the longline is fed out from the stern of the ship and extends one mile. A

Throwing Bait - I'm passing baited gangions to Tim Martin to attach to the Longline. Moments after this photo my TAS hat took flight and joined the sharks of the Atlantic. — Throwing Bait –
I’m passing baited gangions to Tim Martin to attach to the Longline. Moments after this photo my TAS hat took flight and joined the sharks of the Atlantic.

marker, called a high flyer, is attached to the beginning of the line. One hundred baited gangions are attached to the line at intervals after which another high-flyer marks the end of the line. The ship then returns to the starting point, the line is hauled in and the fun begins. If there is a shark on the line, the deck crew fisherman calls out “Shark On!” That’s the signal for someone from the science group to step up and take the shark, remove the hook and collect data.

The following data collected is collected for all sharks:

Species
Precaudal Length: Nose to base of tail
Fork Length: Nose to fork of tail
Natural Length: Nose to tail
Total Length: Nose to end of tail when extended manually
Weight (Kg)
Sex Determination

Tag numbers and tissue sample collection is also noted if applicable.

Early morning haul back by the night shift. Video taken from the highest point on the ship.

Most of the sharks caught were small enough to bring up and hand to the science team. We use a wooden measuring board to determine lengths. Those that were a bit larger were brought up on deck by the fishermen and they required multiple handlers to collect data.

Very large sharks had to be measured with the help of a cradle and hoist. The cradle is lowered to water level and large sharks are coaxed onto the cradle using the hook and line they are still attached to. A hoist brings them to deck height for assessment. Deck Operations Crew manages all shark retrieval and determines when is safe for us to proceed.

Atlantic Sharpnose

Most of the sharks that we’ve caught have been Atlantic Sharpnose. This shark is relatively small (adults average 0.85 M) and are found in shallow Atlantic coastal waters from New Brunswick down into the Gulf of Mexico, and even off the coast of Brazil. They are known by at least 8 common names in different regions. My Biology students would recognize this as a good example of why it’s important to use agreed-upon scientific names for scientific research. The scientific name for this species is Rhizoprionodon terraenova. It has a long snout (longer than the width of the head) and most adults have a few white spots on a gray body.

Sharpnose mature relatively quickly and can begin producing offspring within two years; also, they can have up to 5-7 pups at once. These are major factors contributing to the abundance of this species. In comparison, larger sharks may take up to 15 years to reach maturity and typically have fewer offspring in each brood.

Our catch also included one Blacknose (Carcharhinus acronotus) and multiple Scalloped Hammerhead (Sphyrna lewini), Nurse (Ginglymostoma cirratum) and Spinner sharks (Carcharhinus brevipinna).

Larger specimens were brought to deck height using a cradle, for weight, size, and sex determination, and were lowered back into the water after being measured and tagged.

Nurse Shark in cradle (Photo Credit: Ian Davenport)

A Sandbar shark in the cradle. I'm in the yellow helmet tagging the shark. — A Sandbar shark in the cradle. I’m in the yellow helmet tagging the shark. ( Photo Credit: Erica Nu

Hook removal required bolt cutters after I tagged this Sandbar Shark. — Hook removal required bolt cutters after tagging this Sandbar Shark.

Career Spotlight

If your interests tend toward science mixed with heavy machinery, skilled fishing, robotics or electronics, perhaps one of the following careers is for you.

Tim Martin: Chief Boatswain

As the Chief Boatswain, Tim Martin is responsible of all activities that happen on deck and he maintains constant communication with the bridge during all operations. Tim came to NOAA fisheries with a wealth of experience gained while serving in the U.S. Navy and later as a commercial fisherman in the Pacific Northwest. He was initially classified as a “Skilled Fisherman” with NOAA and has worked his way up to Chief Boatswain.

He and his group set and retrieve the longline. They also run all of the heavy deck equipment, such as the cranes that are used to position the shark cradle for large sharks and the CTD (water Sampling device). The Chief Boatswain is also responsible for training new crewmembers and maintaining ship supplies. In addition, Tim has earned Dive Master Certification through the NOAA Diving School, considered to be the best civilian diving school in the US.

Tim Martin and deck Crew cradling a Tiger shark. Note the wooden dowel at center used to attach tags. ( Photo Credit: Erica Nuss) — Tim Martin and deck crew cradling a Tiger shark. Note the wooden dowel at center used to attach tags. (Photo Credit: Erica Nuss)

When asked what keeps him going, Tim is very clear that he believes the work that NOAA Fisheries does is very important, and he is proud to be able to use his expertise to support NOAA’s efforts. This satisfaction somewhat tempers the challenges of the job which include being at sea for at least 6 months of the year, and constantly being in a training flux. Tim feels a strong bond with his crew and there is a clear sense of mutual trust and respect among them.

Ken Wilkinson: Electronic Technician (Supreme), NOAA Fisheries Engineering Unit

Ken has been with the Engineering Unit of NOAA Fisheries for 26 years. The mission of his Unit is to

Ken using his skills to filet a Red Snapper

support NOAA Fishery research by developing innovative technology. Ken always wanted to work on the water and he initially studied Marine Biology in college, but he migrated toward electronics. His work allows him to combine two great interests. His work takes him to sea 50-80 days each year.

A major focus of the electronics unit is to support the Reef Fish program. Trawling nets and longline apparatus will damage reef systems. In order to assess reef fish populations in a non-invasive way, Ken and his group work a number of Remotely Operated Vehicles that capture still and moving images that can be used later to determine abundance and species diversity. Ken’s unit has also developed a device called an Autonomous Underwater Vehicle (AUV). This programmable instrument scans the sea floor using lasers and data collected is used to develop more accurate sea floor maps.

Bathymetric map of the Longline sampling area- NOAA

New device: Kennenator 5000 Dual Laser

Ken is on board the Oregon II testing his new device that can be used to assess the size of large sharks without bringing them to deck height. Ken’s device has two lasers set at a fixed distance from one another. The beams are directed toward the shark while it remains at the surface of the water. Various measurements can be extrapolated from the laser measurement. Large sharks caught on the longline survey are typically brought to the surface in the cradle for assessment. Cradle use is preferred as it allows tagging and tissue sample collection and sex determination. However, there are situations when this is not possible such as when poor weather conditions develop which limit sling operations, and some small vessels are not equipped with sling equipment.

Personal Log

The fast pace of the haul back at early stations was jarring. I stepped up when “Shark On” was called and a writhing Sharpnose was thrust into my hands. The first task is to get the hook out of the shark’smouth and this is no small feat. The circle hook is designed is to reduce the chance that the shark will swallow the hook or get hurt by it, but getting these hooks out of the mouth without hurting the shark requires technique. There will be plenty of opportunities to get the hang of in the next week.

A highlight of this first day was getting up close to a 2 meter long Scalloped Hammerhead brought to the surface in the cradle. I was able to feel its head, observe its eyes, and place an identification tag near its dorsal fin before it was lowered back into the water.

Smaller Scalloped Hammerhead on deck. It took two of us to hold this one in place fore measuring and tagging. (Photo Credit: Ian Davenport)

June 16, 2015August 21, 2021

Sandra Camp: Who You Gonna Call? Katie Mahaffey! June 16, 2015

NOAA Teacher at Sea
Sandra Camp
Aboard NOAA Ship Hi’ialakai
June 14 – 24, 2015

Mission: Main Hawaiian Islands Reef Fish Survey
Geographical area of cruise: Hawaiian Islands, North Pacific Ocean
Date: June 16, 2015

Weather Data: partly cloudy, visibility > 7 NM (nautical miles), winds east 10-15 KT (knots), air temperature 79° F, water temperature 77° F

Science and Technology Log

During science class this past year, we spent some time studying solutions. We learned what solutes and solvents are, and how to tell when solutions become saturated. We made several saturated solutions ourselves, and even made a supersaturated solution by heating up a solvent so it would dissolve more solute.

One of the things we read about related to the study of solutions was decompression sickness, or “the bends,” a condition that can affect scuba divers if they are not careful. Just like heat, pressure can also allow liquids to become supersaturated. Henry’s Law states that the greater the pressure, the more gas will dissolve in a liquid. Because water pressure is greater the deeper under water you go, a diver’s blood can become supersaturated with gases from the air, such as nitrogen gas. If the diver ascends, or comes up, too quickly, the pressure is decreased too quickly and the nitrogen gas comes out of solution in the form of bubbles (like what happens when you release the pressure on a can of soda by opening it). These bubbles can cause fatigue, joint pain, tingling or numbness, a red rash on the skin, respiratory problems, heart problems, dizziness, blurred vision, headaches, confusion, nausea, or unconsciousness. This condition can be prevented by rising to the surface very slowly after a dive, so that the nitrogen gas is released gradually. Sometimes, however, for different reasons, a diver ascends too quickly and then she/he needs . . . Katie Mahaffey!

Katie’s official position is NOAA Program Support Specialist. She is the ship’s dive master, and she runs the recompression chamber in case any of the divers get decompression sickness. This chamber will help alleviate a diver’s symptoms of decompression sickness by returning them to pressures similar to those under water and gradually decreasing that pressure so the body has time to adjust. I interviewed Katie about her job:

What are your primary responsibilities? Training scientists, engineers, NOAA officers, and technicians on how to dive for NOAA. NOAA has its own policies and procedures for diving, which are important to follow so that everyone can work together well. She also operates the recompression chamber on board the Hi’ialakai, and works with the ship’s medical officer and DMTs (diving medical technicians) to make sure things run smoothly.

What do you love most about your job? Getting to travel for work and seeing different places. Although she lives in Seattle, her job has taken her to visit Gray’s Reef National Marine Sanctuary in Georgia, Key West, Panama City, and Kodiak, Alaska. And now, Hawaii!

What kind of education do you need to have this job? After graduating college, Katie went to commercial diving school, which teaches people to dive for applications like underwater welding and working in caissons. As an intern at NOAA, she completed all NOAA scuba dive training. She also trained to be an EMT (emergency medical technician). She says that NOAA is very good about providing training for their staff. All you have to do is ask.

Do you have any advice for young people interested in your line of work? It is important to have a strong scientific background, especially physics, anatomy, and physiology. (As a side note, don’t worry if you think you can’t dive because you get seasick. Katie is an expert on diving, but she does get sea sick! She simply wears a patch that provides her body with medicine to prevent motion sickness.)

Personal Log

As I stated in my first blog, the mission of this cruise is to survey the coral reefs around the main Hawaiian Islands to see if they have healthy populations of reef fish living among them. The first island we visited was Molokai. Two of the divers saw a hammerhead shark that day.

From the deck of the ship, I saw a place on the island that locals say is shaped like a shark: Kalaupapa, a former colony for people suffering from Hansen’s Disease, formerly known as leprosy. In the past, Hansen’s disease spread easily and was incurable, so people thought the best way to deal with it was to separate those infected from the rest of the population. Because Kalaupapa is a peninsula surrounded on 3 sides by water, and cut off from the rest of Molokai by huge sea cliffs, it was thought to be a good location to place people suffering from this disease.

Beginning in 1866, people with the disease were shipped to this location to live without basic amenities, such as buildings, food, shelter, and fresh water. The first arrivals had to fend for themselves and lived in caves or shacks built out of sticks and leaves. In 1873, Father Damien deVeuster, a Catholic priest from Belgium, arrived and worked hard to improve life for the residents of Kalaupapa. Although Hansen’s Disease has since been cured, a few former patients choose to remain there, and still live in Kalaupapa today.

Here is a picture of the daily work board. On it is written the times for important meetings, the names of the divers and what boats they will be working from, and other information important to the mission. As you can see, there is a Photo of the Day that gets posted on the NOAA CRED (Coral Reef Ecosystem Division) Facebook page. Yesterday, one of my photos was the winner of the Picture of the Day, and this morning, I was presented with the prize of a huge lollipop. You might also notice that I will be taking head shots of the science team for a poster we will be creating. Another important event is “8-Minute Abs,” led nightly by Paula, one of the scientist-divers. My abs are a bit sore!

Did You Know?

Hammerhead sharks seem to have their eyes in a strange place, but it actually improves their ability to see prey. They are found in temperate and tropical waters all over the world, and can sometimes be seen prowling around reefs for food.

New Terms

caisson – a large, watertight chamber which is open at the bottom that lets workers carry out construction under water