shark abundance survey – NOAA Teacher at Sea Blog

August 15, 2018August 16, 2018

Stephen Kade: How Sharks Sense their Food & Environment, August 9, 2018

NOAA Teacher at Sea

Stephen Kade

Aboard NOAA Ship Oregon II

July 23 – August 10, 2018

Mission: Long Line Shark/ Red Snapper survey Leg 1

Geographic Area: 30 19’ 54’’ N, 81 39’ 20’’ W, 10 nautical miles NE of Jacksonville, Florida

Date: August 9, 2018

Weather Data from Bridge: Wind speed 11 knots, Air Temp: 30c, Visibility 10 nautical miles, Wave height 3 ft.

Science and Technology Log

Sharks have senses similar to humans that help them interact with their environment. They use them in a specific order and rely on each one to get them closer for navigational reasons, and to find any food sources in the area around them. The largest part of the shark’s brain is devoted to their strong sense of smell, so we’ll start there.

snout of Tiger shark

snout of sharpnose shark

Smell– Sharks first rely on their strong sense of smell to detect potential food sources and other movement around them from a great distance. Odor travels into the nostrils on either side of the underside of the snout. As the water passes through the olfactory tissue inside the nostrils, the shark can sense or taste what the odor is, and depending which nostril it goes into, which direction it’s coming from. It is said that sharks can smell one drop of blood in a billion parts of water from up to several hundred meters away.

Sharks can also sense electrical currents in animals from long distances in several ways. Sharks have many electro sensitive holes along the snout and jaw called the Ampullae of Lorenzini. These holes detect weak electrical fields generated by the muscles in all living things. They work to help sharks feel the slightest movement in the water and sand and direct them to it from hundreds of meters away. This system can also help them detect the magnetic field of the earth and sharks use it to navigate as well.

Hearing– Sharks also heavily use their sense of smell to initially locate objects in the water. There are small interior holes behind their eyes that can sense vibrations up to 200 yards away. Sound waves travel much further in water than in the air allowing them to hear a great distance away in all directions. They also use their lateral lines, which are a fluid filled canal that runs down both sides of the body. It contains tiny pores with microscopic hairs inside that can detect changes in water pressure and the movement and direction of objects around them.

Sight– Once sharks get close enough to see an object, their eyes take over. Their eyes are placed on either side of their head to provide an excellent range of vision. They are adapted to low light environments, and are roughly ten times more sensitive to light than human eyes. Most sharks see in color and can dilate their pupils to adapt to hunting at different times of day. Some sharks have upper and lower eyelids that do not move. Some sharks have a third eyelid called a nictitating membrane, which is an eyelid that comes up from the bottom of the eye to protect it when the shark is feeding or in other dangerous situations. Other sharks without the membrane can roll their eyes back into their head to protect them from injury.

Touch– After using the previous senses, sometimes a shark will swim up and bump into an object to obtain some tactile information. They will then decide whether it is food to eat and attack, or possibly another shark of the opposite gender, so they can mate.

Taste– Sharks are most famous for their impressive teeth. Most people are not aware that sharks do not have bones, only cartilage (like our nose and ears) that make up their skeletal system, including their jaw that holds the teeth. The jaw is only connected to the skull by muscles and ligaments and it can project forward when opening to create a stronger bite force. Surface feeding sharks have sharp teeth to seize and hold prey, while bottom feeding sharks teeth are flatter to crush shellfish and other crustaceans. The teeth are embedded in the gums, not the jaw, and there are many rows of teeth behind the front teeth. It a tooth is damaged or lost, a new one comes from behind to replace it soon after. Some sharks can produce up to 30,000 teeth in their lifetime.

Sandbar Shark teeth

Great Hammerhead Shark teeth

Personal Log

While I had a general knowledge of shark biology before coming on this trip, I’ve learned a great deal about sharks during my Teacher at Sea experience aboard the Oregon II. Seeing, observing, and holding sharks every day has given me first hand knowledge that has aided my understanding of these great creatures. The pictures you see of the sharks in this post were taken by me during our research at sea. I could now see evidence of all their features up close and I could ask questions to the fishermen and scientists onboard to add to the things I read from books. As an artist, I can now draw and paint these beautiful creatures more accurately based on my reference photos and first hand observations for the deck. It was amazing to see that sharks are many different colors and not just different shades of grey and white you see in most print photographs. I highly encourage everyone that has an interest in animals or specific areas of nature to get out there and observe the animals and places firsthand. I guarantee the experience will inspire you, and everyone you tell of the many great things to be found in the outdoors.

TAS Stephen Kade with a sharpnose shark

TAS Stephen Kade removes the hook from a sharpnose shark

Animals Seen Today: Sandbar shark, Great Hammerhead shark, Sharp nose shark

July 1, 2006March 19, 2021

Brenton Burnett, July 1, 2006

NOAA Teacher at Sea
Brenton Burnett
Onboard NOAA Ship David Starr Jordan
June 26 – July 6, 2006

Mission: Shark Abundance Survey
Geographical Area: California Coast
Date: July 1, 2006

A hooked pelagic ray swims aside the DAVID STARR JORDAN.

Weather Data from Bridge
Visibility: 10 nautical miles (nm)
Wind direction: 315 degrees
Wind speed: 12 kts
Sea wave height: 1’
Swell wave height: 2-4’
Seawater temperature: 19.6 degrees C
Sea level pressure: 1012.5 mb
Cloud cover: Clear

Science and Technology Log

Today’s first run was sharkless but instead we did catch eight pelagic stingrays. In the afternoon we caught two smaller makos and another ray. As I mentioned yesterday, chimera, skates and rays, and sharks make up Class Chondrichthyes. The chimera are the most ancient grouping of these cartilaginous fish. Later came the skates, rays, and sharks in the Subclass Elasmobranch which make up 96% of the cartilaginous fish species. In general, the rays and skates are characterized by a flattened body with their pectoral fins fully attached to the head. This design is an adaptation to living on the seafloor. Creatures that live here are described as benthic. This lifestyle is in contrast to sea life that lives in the open ocean, which is described as pelagic.

Which of the toy models is a ray and which is a skate? Skates have dorsal fins located near the ends of their tails

The pelagic stingray is the only stingray that is not benthic. This behavior may be a relatively recent occurrence on evolutionary time scales, however, as it retains a number of characteristics best designed tails. Like all skates and rays, their mouths are located under their flattened body. In this position, they can swim along the bottom and suck in prey off the seafloor. I recently witnessed such feeding as I fed a bat ray at SeaWorld last week.

The gills of skates and rays (collectively known as the batoids) are located underneath, or ventral, to the body. When resting on the bottom, water flow through the gills is limited and so obtaining oxygen would be a problem if it weren’t for another feature common in cartilaginous fish, the spiracle. Most sharks also have spiracles, which are small holes on either side of their head. They have a respiratory function. In rays and skates these spiracles are located just behind the eyes up on the top of the head. When the pelagic rays are out of the water, the opening and closing of the spiracles as they breathed was obvious. There are two features most useful in distinguishing a skate from a ray. Most skates have one or two dorsal fins located far back on their tails, and they never have spines that are typical of rays.

The spine of a ray is often toxic and used as a defense by the ray. When the pelagic rays were brought on board, the first priority was the safety of the humans. The spine was snipped or if possible, the ray is placed upside down on foam that ultimately will take a spine “hit” and from then on cover the spine. The toxin of a ray’s spine is not delivered in the way a snake’s fangs might inject its poison. A ray’s spine is serrated and acts like a harpoon or barbed hook, preventing removal in the opposite direction from which it was inserted. The spine of a stingray has serrated edges but is in the form of a mucous that fills two that make it virtually impossible to remove a grooves on the underside of the spine.

The spiracles of a stingray are located just behind the eyes. The spine, sometimes two or three of them, is found near the base of the tail.

A pelagic ray is on the shark platform belly up. Its spine is safely lodged into the foam. A puncture made by the spine that may then be infected by the toxic mucous. Telling shark from batoid is not always easy. The order of sharks known as angel sharks bear resemblance to batoids but their pectoral fins are clearly not fully attached to the head, and their mouths are at the front of the head and not underneath as it is in all rays and skates. Other kinds of sharks and rays that can be confused are the sawshark, which is a shark, and the sawfish, which is a ray. Both have a bizarre flattened snout from which teeth stick laterally, or sideways, outwards. They both have a thicker more sharklike body. Both have two dorsal fins, a set of pectoral fins and a set of pelvic fins. But they are no more closely related than any shark is to any ray. When two different types of animals (or plants, or other living thing) are faced with similar challenges, they can sometimes independently evolve in a way that arrives at a similar solution. Bats, birds and butterflies each independently evolved flight. Triceratops and rhinos evolved head horns. Mako sharks and dolphins evolved sleek torpedo shaped bodies for rapid swimming.

And sawsharks and sawfish have independently evolved a saw shaped snout. Each is believed to use their snout to capture and kill prey. But they also retain their sharkiness Angel sharks are flattened like a ray but their pectoral fins are distinctly unattached from the head. Angel sharks have mouths at the front of the head while all batoids have mouths located ventrally, or under the body. There five known species of sawsharks. They, like most other sharks, have their gill slits on the sides of their head. Also, their pectoral fins are not fully attached to the head. Sawsharks have a pair of barbels coming from the sides of their snouts, giving them a mustachioed appearance. Sawsharks like other sharks have a sensitivity to the electrical disturbances created by moving fish and other prey. Their snout enhances this sensitivity. But the sawfish has no such electrical organ. The sawfish does have pectoral fins that attach fully to the head where the sawshark’s pectoral fins do not. Additionally, the pectoral and pelvic fins of the sawfish are flatter and more flush with the body. And the gills of the sawfish are underneath the head, but they are found on the side of the head on the sawshark. Lastly, another feature that distinguishes the two are the sawshark barbels that stick out from the middles of their snouts like moustaches—sawfish do not have these.

The spine of a stingray has serrated edges that make it virtually impossible to remove a spine by simply pulling it out the way it went in.

I need to address a couple of student questions that I don’t believe I’ve yet answered:

Oxytetracycline (OTC), the dye used to stain the vertebrae for aging studies, is not known to do harm to the shark if given in excess. However, a table of calculated dosages based on length is used because if too much OTC is used, growth layers other than just the present one will also become stained.

The J-hooks typically used are about four inches in length. The shark abundance survey has been going on since 1994, and to maintain consistent and scientifically comparable data, they continue to use these hooks.

Sharks have few enemies in the oceans. They tend to be the top predators in their food webs, but as the vast majority of sharks are less than one meter (three feet) long, they can be come prey for other, larger sharks, or even whales like orca. By far the species that poses the largest threat to them are humans. Mostly humans kill sharks when it is other types of fish that meant to be caught. The shark would then be referred to as “by-catch”. At other times sharks are intentionally caught for their meat or as sport—this is often the case for mako sharks.

Angel sharks are flattened like a ray but their pectoral fins are distinctly unattached from the head.

Sawfish have their gills located underneath their head like all other batoids.

Oxytetracycline is light sensitive, meaning it reacts and breaks down when exposed to enough light. For this reason the bottle is brown and kept in a bag, and loaded syringes are kept inside a glove for ready use.

The J-hook and somewhat smaller circle hook are used for mako and thresher shark lines.

Personal Log

I continue to have a good time here, if not for the sights and sounds but for the people I am working with. Lots of interesting, friendly, and fun-loving folks. And, happily, they have been quite tolerant, and even obliging of me walking around with my video camera catching this and that.

Angel sharks have mouths at the front of the head while all batoids have mouths located ventrally, or under the body.

There five known species of sawsharks. They, like most other sharks, have their gill slits on the sides of their head. Also, their pectoral fins are not fully attached to the head.

Sawsharks have a pair of barbels coming from the sides of their snouts, giving them a mustachioed appearance.

Sawfish have their gills located underneath their head like all other batoids.

Oxytetracycline is light sensitive, meaning it reacts and breaks down when exposed to enough light. For this reason the bottle is brown and kept in a bag, and loaded syringes are kept inside a glove for ready use.

The J-hook and somewhat smaller circle hook are used for mako and thresher shark lines. — The J-hook (right) and somewhat smaller circle hook are used for mako and thresher shark lines.

June 30, 2006March 19, 2021

Brenton Burnett, June 30, 2006

NOAA Teacher at Sea
Brenton Burnett
Onboard NOAA Ship David Starr Jordan
June 26 – July 6, 2006

Mission: Shark Abundance Survey
Geographical Area: California Coast
Date: June 30, 2006

Weather Data from Bridge
Visibility: 10 nautical miles (nm)
Wind direction: 250 degrees
Wind speed: 9 kts
Sea wave height: <1
Swell wave height: 1-2’
Seawater temperature: 17.6 degrees C
Sea level pressure: 1015 mb
Cloud cover: Clear

Russ Vetter and Rand Rasmussen position a blue shark so they can measure its length and remove the hook.

Science and Technology Log

Today was a slower day in terms of numbers of sharks—we only caught three. But the mood was good because each of the sharks caught was large enough to accommodate satellite tags. And, we caught one of each species of shark that we anticipate seeing—a blue, a thresher and a mako. The mako was particularly lively giving a good kick as it left the shark trough. Any of the sharks tagged on this trip, or others in the same effort, can be monitored here. On this cruise we have attached SPOT tags to two makos (on Tuesday #60986 and today, #60998), a blue (#60989) and a thresher (#53797). Note: I’m told that all four of these MAY be listed as blues on the website until the website is fully updated, but the tracks of all four sharks should be viewable right now!

All sharks are in the phylum Chordata. They, along with rays and skates, and a strange and even more ancient group of fish called chimera, make up Class Chondrichthyes, which are the fish with skeletons made of cartilage. The only bony material in a shark is its teeth and for this reason very few shark fossils beyond teeth are found. The other classes of chordates are the jawless fishes (hagfish and lamprey), the bony fishes (minnows, mola, cod, seahorses, etc.), amphibians, reptiles, mammals and birds.

The goblin shark—perhaps the ugliest shark ever!

Each class is divided up into orders, and there are eight orders of sharks— one order includes the sawsharks, another the whale shark and wobbegong, and another the angelsharks (which have some resemblance to rays). The frilled and cow sharks make up another order, the bullhead sharks another, and there is an order for the dogfish sharks (including the spiny dogfish which might be the most numerous of all shark species—closer to shore, we may hook one). All of these orders are sharks but when people think of sharks they typically envision either mackeral sharks, which include great whites, makos, tigers and threshers, or the ground sharks, which include leopard sharks, hammerheads and blue sharks.

The 16 species of mackeral sharks are among the most specialized of sharks. Many, like the mako, are swift swimmers. Threshers have a tail that is as long as the rest of their body is. It is believed that they use this tail to “corral” fish and then slap the fish to stun them. The goblin shark lives in the dark of the deep and has a strange snout jaw structure that makes it arguably the ugliest shark. The first of these was caught in 1897 near Japan. A scientist there delivered it to Professor David Starr Jordan, for whom the National Oceanic and Atmospheric Administration ship we are on is named.

The DAVID STARR JORDAN awaits the return of its Zodiac boat. — The ship awaits the return of its Zodiac boat.

With over 200 species, the ground sharks are the most diverse and varied order of sharks. The blue shark is a generalist living in open waters in nearly all of the world’s oceans. Others, like the catsharks are benthic, or bottom-dwelling. Most are small and harmless but some are the largest of predatory sharks. All of them have what’s called a nictitating eyelid which covers the eyes to protect them as the shark bites.

Personal Log

During today’s afternoon set, we inadvertently lost a buoy that was intended to be clipped to the longline. Fortunately, such a mishap is occasion to let loose the ship’s two engine Zodiac. Myself, Stephanie Snyder (an intern with NOAA), Miguel Olvera, and crewmembers Chico Gomez and David Gothan, set out to retrieve it. The buoy was dropped early in the set so we had to travel a couple miles out. On the way, we briefly saw four molas. Later a sea lion passed by.

An adventure here, an adventure there—the fifth day is as interesting as the first!

June 29, 2006March 19, 2021

Brenton Burnett, June 29, 2006

NOAA Teacher at Sea
Brenton Burnett
Onboard NOAA Ship David Starr Jordan
June 26 – July 6, 2006

Mission: Shark Abundance Survey
Geographical Area: California Coast
Date: June 29, 2006

Weather Data from Bridge
Visibility: 10 nautical miles (nm)
Wind direction: 306 degrees
Wind speed: 15 kts
Sea wave height: 1-2’
Swell wave height: 2-3’
Seawater temperature: 19.8 degrees C
Sea level pressure: 1017 mb
Cloud cover: Partly cloudy

The beaks of a variety of squids and a fisheye lens found in a blue shark’s stomach.

Science and Technology Log

While today’s catches were lighter than yesterday’s, there were some very interesting new sights to see. One blue shark that made it up on deck, threw up some of its stomach contents. Out came the remains of a pelagic (open water) crab and a number of squid beaks. The largest of these beaks was three centimeters (just over an inch) in diameter and the smallest less than a half a centimeter. Blue sharks are perhaps the most widely distributed shark, living in all oceans except in the polar latitudes. As such, they are generalists and eat squid, fish, smaller sharks and even birds. Jacques Cousteau even filmed blues shepherding virtually invisible krill into balled clusters so they could swim through the ball to feast. While setting the afternoon line, I saw a curved tip dorsal fin break the surface off the starboard bow. Then it disappeared under a wave. Moments later as we caught up to it, a large disc of a fish could be seen below the fin—a mola!! Molas are the largest bony fish though they are not the largest of all fishes. That honor belongs to the docile plankton-eating whale shark. Molas can reach a length over 4 m (13 feet), though the one we saw was closer to 2 m (6 feet). Whale sharks, however, can grow to over 20 m (70 feet) long.

Bottlenose dolphins porpoising in front of the bow of the DAVID STARR JORDAN. — Bottlenose dolphins porpoising in front of the bow

Later, as we hauled the afternoon set, another mild surprise—a pelagic stingray was caught on our line! Once aboard, the highest priority was to disarm the poisonous spine projecting from the base of the stingray’s tail. While Sean Suk, another Southwest Fisheries Science Center (SWFSC) researcher, held the ray down, Suzy Kohin was able to clip the spine disabling the ray, but not harming it. Rays and skates evolved flattened bodies as an adaptation as benthic, or bottom feeders. Rays and skates, or batoids as they are called collectively, have a mouth positioned on the bottoms of their bodies so they can best feed along the bottom of the ocean. Pelagic rays, as their name implies, live in the open ocean. So the pelagic ray has evolved a unique style of feeding. When approaching a school of fish, this ray will turn upside down and curl its wings above it forming a funnel. This funnel shape directs the fish right to its mouth.

In the evening, after our work was done for the day, a few of us were on the stern deck when a school of dolphins approached. Soon they surrounded the ship and a group of six or seven stayed with us porpoising at our bow for close to thirty minutes! “Porpoising” is the arched jumping above the water as dolphins swim. This behavior allows these mammals to breathe while maintaining their pace. Porpoising should not be confused with breaching which is a more vertical jump from the water. Breaching behavior has been observed in a number of whale species, but also in some sharks. The two shark species best known for breaching happen to be the two species we are most interested in on this cruise—makos and threshers. Scientists are not certain why whales breach, nor are they entirely certain why sharks breach. At least a partial answer may be that they are making an attack on prey. Many sharks, not just blues, are known to eat sea birds, and makos, specifically, have been seen jumping from the water in attempts to attack floating sea birds. White sharks, the larger cousins of makos, are known to breach but in False Bay near Dyer Island off South Africa, this behavior could even be described as common. The unique seafloor topography there forces the southern fur seals to repeatedly swim from surface to seafloor as they make their way to the island (if they didn’t they would be eaten by the sharks outright). Researchers have discovered that as the great whites pursue the seals from the depths their momentum takes them up and fully out of the water in spectacular breaches.

Personal Log

Every day on board brings something new to this mountain man. On deck, when critters aren’t appearing on board or in the sea, there are always science folks to answer questions. Of course, that is when they aren’t watching World Cup soccer via the satellite TV. ‘Til, tomorrow…

June 28, 2006March 19, 2021

Brenton Burnett, June 28, 2006

NOAA Teacher at Sea
Brenton Burnett
Onboard NOAA Ship David Starr Jordan
June 26 – July 6, 2006

Mission: Shark Abundance Survey
Geographical Area: California Coast
Date: June 28, 2006

Weather Data from Bridge
Visibility: 10 nautical miles (nm)
Wind direction: 300 degrees
Wind speed: 17 kts
Sea wave height: 2-3’
Swell wave height: 3’
Seawater temperature: 19.6 degrees C
Sea level pressure: 1015 mb
Cloud cover: Scattered clouds

A National Marine Fisheries Service (NMFS) tag and insertion tool. — NOAA Fisheries tag and insertion tool

Science and Technology Log

Dr. Kohin, our chief scientist, tapped me to assist on the shark platform this morning! This means I helped remove the hook from sharks’ mouths and helped with the tagging. Note: I didn’t get bit once nor was I lost overboard. And the sharks did well, too. There are many tasks that lead up to shark tagging and hook removal. As the long line is drawn in by electric winch, one member of the science team unclips the gangion (or the buoy) and passes it on to others for stowing. If no catch was made on that hook (which is the case most of the time), the bait has to be removed before stowing. If there is a shark, however, it is walked “on its leash” to the stern (back) of the ship to the shark platform where Russ Vetter and Rand Rasmussen (and often Suzy Kohin though she is also busy coordinating the efforts of everyone) work to collect data and release the animal. Others record data and provide the materials necessary for tagging. As is often the case when conducting scientific research, much of this work can be repetitive. But when something comes in on the line, or when something unexpected happens like when a gangion is twisted on a line, there is lots of activity and excitement.

To be sure, the most excitement is on the shark platform. This 4 foot by 8 foot (approximate) platform is connected along its long side to the shark trough. The shark platform is accessed from the deck by a large chute that is as wide as the platform is long.

The shark trough is lowered just under the water until the shark (still on the line) can be maneuvered into the shark trough by Russ. Once there, Russ and Rand are quick to hold down the shark so that they can safely work on it. Rand uses a small thick blanket to cover the shark’s mouth and sharp teeth. Before releasing the animal, however, he needs to remove the hook. While the two of them hold the shark, another person (which was me this morning) cuts the hook or wire lead. By this time the sex of the shark has been determined. This is easily accomplished by observing the rear underside of the shark— two finger like “claspers” near the pelvic fins are present if the shark is a male. The last step before releasing the shark is to measure its length. A meter stick along the edge of the trough makes this an easy task.

If the shark is a mako or a thresher, however, a number of other tasks are undertaken before hook removal and release of the shark. First, a National Marine Fisheries Service (NMFS)”spaghetti tag” is attached just forward and to the side of the dorsal fin. These are “conventional tags” which give the animal a number and provide an address to send the tag to if the animal were recaught. The spaghetti tag is barely more than a plastic wire attached to a pointed piece of metal. To insert it, a small incision is first made in the shark’s back. Then, using an awl shaped tool, the metallic portion of the tag is wedged through the incision just under the skin. Because these tags may not stay in for life, a backup tag is also used. These are called ROTO tags and they are attached directly to the dorsal fin. Sharks returned with ROTO tags also indicate to researchers that oxytetracycline has been injected into the shark. These tags, like others, contain reward information for the return of specimens or information about them.

For larger and healthier sharks, satellite tags, of which there are two, may be attached to the shark. The SPOT tag (smart position and temperature tag) is a bit thinner and smaller than a computer mouse. Attached to the dorsal fin (in lieu of the ROTO tag), the SPOT tag has two metal washers on its exterior. If the shark rises to the surface, with its dorsal fin out of the water, these washers dry long enough to disrupt the electrical current that normally passes between them through the water. This cues the tag to transmit the shark’s position to a satellite. Using these tags costs more than $2,000 each, so it is important to use them with animals that are large enough to receive them and ones who are in good health.

If a shark receives a SPOT tag, a PAT tag (popoff and archival tag) will also be attached. The PAT tag records water temperature, depth and light levels at one minute intervals. After a few months or some other specified time, the tag is designed to pop off and float to the surface. At that time the tag transmits a summary of its data collection to researchers via satellite. If the PAT tag can actually be recovered, the full set of data at its full resolution can be retrieved.

It is interesting to note that light levels act as a proxy for time of day given that noon and midnight can easily be determined from them. And, in turn, this information can be translated into a longitudinal position as one notes the shift of day time from the location of tagging. Light level can also be used to determine latitude as on all days except those nearest the equinoxes, the length of day is dependent upon how far one is north or south.

Between the SPOT and PAT tags, the horizontal as well as vertical movement of the animal can be tracked over a period of time. Using only conventional tags, only one additional location can be mapped, and that only with a recatching of the animal. With these methods, it is hoped that the travels of these young makos and threshers, will be better understood as they feed and breed.

Personal Log

Every day has been exciting, but today helping on the shark platform has topped it all. I was lucky, too, as that set was the most productive, so far. We caught 57 sharks on 202 hooks—a pretty good batting average. And five of these were makos. We also caught a larger thresher shark, rare out this far. I was thrilled to think I’d get to see this guy up close, but alas it was not to be. The thresher threw the hook and escaped—the big one got away! Fortunately, later in the trip we’ll likely be more in thresher waters!

June 27, 2006March 19, 2021

Brenton Burnett, June 27, 2006

NOAA Teacher at Sea
Brenton Burnett
Onboard NOAA Ship David Starr Jordan
June 26 – July 6, 2006

Mission: Shark Abundance Survey
Geographical Area: California Coast
Date: June 27, 2006

Weather Data from Bridge
Visibility: 10 nautical miles (nm)
Wind direction: 350 degrees
Wind speed: 9 kts
Sea wave height: 1’
Swell wave height: 2-3’
Seawater temperature: 20.0 degrees C
Sea level pressure: 1012.7 mb
Cloud cover: Cloudy

The mako sharks we catch are one to two years old and are between 70 cm and 140 cm (around 3 feet) long.

Science and Technology Log

Our first full day of setting and hauling netted 68 sharks. In the morning we caught 21 blues and 5 makos, and in the afternoon 39 blues and 3 makos. Unfortunately, one mako and one blue did not survive and were brought aboard for sample collections. Though everyone involved understands that the work being done here is ultimately about helping these sharks survive and thrive in the wild even when an animal dies, there is, among everyone, a definite sense of loss and regret when an animal is lost. The data collection process involves a great deal of care for that reason.

Studies have been done to look at the stress related hormone levels of sharks caught on long lines, and the length of “soak times” used in this project follow those recommended guidelines—three to four hours from the start time of setting the line to the start of hauling it in. The design of long line helps to maximize survival, too. The gangions, which are the lead and hook assembly that attach to the long line, are about three meters long which gives these sharks room to swim while hooked. This is important for blues and makos as they, like many other sharks, need to keep in constant motion so fresh, oxygen-rich water is always moving through their gills.

Another challenge is that, on occasion, a shark will swallow the hook, so whenever possible a “circle hook” is used that will not hook in the stomach or esophagus, but only on a “corner” of some kind. If a circle hook is swallowed it will get pulled out by the shark’s movement away from the line but when the animal turns away, the circle hook will catch in its mouth. Even if a hook, like a J-hook, cannot be removed from an animal because it was swallowed, this does not necessarily mean it will die. Sharks with hooks in them have been released and recaught years later. When a shark does die, its body is utilized to understand sharks better. This is especially true for the mako sharks. Dr. Jeff Graham and two of his students, Dovi Kacev and Noah Ben-Aderet, as well as Miguel Olvera, another graduate student, are collecting a number of tissue samples for themselves and others at their home universities.

The gills of the mako sharks are of interest because makos are a high-performance, speedy, shark. A comparative anatomy study is being done to compare the design of their gills to that of tunas, another high-performance fish, though tunas are in the class of bony fishes, Osteichthyes, and sharks are cartilaginous being members of Class Chondrichthyes. For this reason, the gills of available specimens are being collected.

Shortfin makos (and, incidentally, common thresher sharks which also might be seen on this trip) are among the very few warm-blooded species of shark. Higher temperatures facilitate their higher energy usage as the fastest sharks in the ocean. Makos achieve higher body temperatures, in part, because their “red muscle” tissue is located close to the spinal column and not, as in most other sharks, close to the skin. This red muscle is responsible for maintaining prolonged periods of powerful movement. This muscle works in tandem with the circulatory system to create a heat exchange system called countercurrent circulation. The internal location of the red muscle and the countercurrent circulation work to preserve heat and even warm the blood before it reaches the heart. For these reasons, studies are being conducted on the red muscle versus white muscle are being sampled for later examination.

Because of the mako’s high performance, and the relation of that performance to the circulatory system, heart tissue is also being collected. The vertebrae of the makos is being collected, too, for the purposes of trying to determine the ages of the animals. This was discussed some yesterday in the discussion of oxytetracycline injections.

Finally, a cutting from a fin is also being collected to later extract DNA. Relatively little is known about the movement of makos (hence our tagging of them). By examining the genetic relationship of makos sampled, researchers will be able to determine if makos off the California coast are related to makos in other parts of the Pacific, including the southern hemisphere.

Personal Log

Aside from the critters at hand, there have been lots of other activity to feed our curiosities. We’ve been seeing whale spouts, probably fin or blue whales, and Risso dolphins. Ann Coleman, an aquarist with Monterey Bay Aquarium and another member of the science team, suggested we might even see some molas! Molas are the largest bony fish in the world reaching 1500 pounds and a record of 14 feet in total length! We can hope!

Thankfully, I’ve had zero issues with seasickness. In fact, I’ve rather enjoyed being rocked to sleep at night. And, thankfully, the food has been plentiful and quite yummy! That’s all for now…

Brenton

June 26, 2006March 19, 2021

Brenton Burnett, June 26, 2006

NOAA Teacher at Sea
Brenton Burnett
Onboard NOAA Ship David Starr Jordan
June 26 – July 6, 2006

Mission: Shark Abundance Survey
Geographical Area: California Coast
Date: June 26, 2006

The DAVID STARR JORDAN awaits final fueling and preparation for our cruise.

Science and Technology Log

The DAVID STARR JORDAN was first commissioned by the U.S. Bureau of Fisheries, which later became part of the National Oceanic and Atmospheric Administration. Since its commission, it has logged over a million miles studying the biological and physical oceanography of the southwestern U.S. coast and eastern tropical Pacific. While it has a range of 7500 nautical miles (nm) and can be out to sea for 30 days, our cruise will last for 10 days and cover only a few hundred nm. It can berth up to 33 people, but on board this cruise are 12 officers, engineers and crew, and 12 scientists including myself. In ideal conditions, the top cruising speed of the DAVID STARR JORDAN is 10 knots (about 12 mi/hr).

This mission’s goals are to assess shark abundance in the Pacific off the coast of California. This is done through long line fishing. At 1800 hours and approximately 20 nm out from San Diego, we made our first “set”. Making a set is truly a team effort involving no fewer than five of the ship’s crew and eight scientists. The crew run the winches and navigate the ship, while the science team baits and sets the line. Two people ready the “gangions”—a gangion consists of a 4” J-hook, an 8’ wire lead and a “tuna clip”. These two pass the gangions on to two others who bait each hook with a whole mackerel, which is about a 10” fish. The baited gangions are then given to the “hooker” who clips them to the line that is running along the side of the ship and then back beyond the stern. Two others are readying balloon buoys that are attached between every five hooks. The length of the lead on the buoys, which is about 7 meters, plus the length of the gangions, about 3 meters, determines the depth of the baited hooks.

We baited 113 hooks along about 1.5 nm of line and let it soak for one hour. At dusk we began to “haul” the line in. This, too, requires a team effort. Tasks include removing the gangion from the line, “de-baiting” the hook, and stowing the gangion. Of course, if there’s a catch, then it’s really exciting. The shark, still in the water on a hook, is walked to the stern to the shark platform. There, senior scientists, Russ Vetter and Rand Rasmussen, and chief scientist Suzanne Kohin slide the shark into the shark trough, which is then quickly raised just above the water. While two of them hold the shark, they remove the hook, measure and determine the sex of the shark. All mako shark and thresher sharks will get a tag of one variety or another. Though, most of our catches will be blue sharks, other researchers, specifically those at the Pacific Island Fisheries Science Center (PIFSC), are tagging blue sharks.

Oxytetracycline is injected to some specimens, too. OTC dyes the vertebra of the sharks. The vertebra, like the rings of a tree grow layers over time. It is not certain how often these layers form, one study suggests two in a year. Injected sharks that are recaught later will help to answer this question, and ultimately help scientists understand how quickly sharks age and reach maturity. Incidentally, recatches of this sort are typically done by fisherman who are given $100 for recording the shark’s length, the date it was caught, and for returning four to five vertebrae.

Our first set of the trip was a practice run of about 1.5 nm and 113 hooks. The haul brought in four blue sharks and one mako. From here on out, we’ll be making 2 two mile long sets a day with 200 or so hooks.

Personal Log

Though we had a delayed start to our cruise—the two diesel trucks to fuel up the ship were late—there has been very little down time! Now that I’ve been able to check email, I’ll get to questions next time! Until then… Brenton