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.

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.

Ampullae of Lorenzini and nostrils

Ampullae of Lorenzini and nostrils of a sharpnose shark

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.

Ampullae of Lorenzini and nostrils

Ampullae of Lorenzini and nostrils of a sharpnose shark

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.

dilated pupil of sharpnose shark

dilated pupil of sharpnose shark

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.

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.

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

Karen Grady: One Fish Two Fish Red Fish …… Weird Fish, April 10, 2017

NOAA Teacher at Sea

Karen Grady

Aboard NOAA Ship Oregon II

April 5 – April 20, 2017

Mission: Experimental Longline Survey

Geographic Area of Cruise: Gulf of Mexico

Date: April 10, 2017

Weather Data

Latitude 2827.10
Longitude 09148.6
75 degrees
Sunny
No precipitation
Winds at 10 KTS
Waves at 2-4 FT

Science and Technology Log

We have continued to move between deep stations setting the baited line and hoping to catch deep water fish and sharks. These deep sets require longer soaking time to allow the hooks to reach the bottom.   The downside is that we have been retrieving one set of gear and putting out one set of gear in a 12 hour period of time. Some sets have a few fish and some we get a big goose egg.   There is always anticipation though as the 100 hooks are brought up. Everyone stands in their spots waiting to hear either “fish on,” “shark” or everyone’s favorite, “hard hats!” which means there is a big shark and it’s time for the sling. Below you will see the awesome Great Hammerhead (Sphyrna lewini) we caught.

TAS Karen Grady 4-13-17 great hammerhead

Great Hammerhead Shark

The first few days we have been fishing deep in the Mississippi Canyon. The Mississippi Canyon is a geological formation in the Gulf of Mexico. It is located in an area which is part of the territorial waters of the United States. We put out some deep lines with the deepest at 1900 feet. These lines soaked four hours once fully deployed.  They soak longer because they have so far to sink to get to the depth the scientists want to fish at. When we deploy a line the first thing in the water is the High Flyer, which stands like a beacon and bobs in the water marking the start of our fishing line. The next thing over the side of the ship is a weight that helps carry the line to the desired depth. Halfway through, another weight is deployed, and after the 100th hook, the third weight goes in.   The last thing over is another High Flyer to mark the end of the line. If it is dark outside, the High Flyers have lights attached on top that flash so that they can be seen.

TAS Karen Grady launching high flyer

“High Flyers” mark the beginning and the end of the long line set.

At our last deep station we caught a Mexican Grenadier, Coryphaenoides mexicanus. This fish is very unusual in color and appearance. If you feel the scales on the fish you find that they are very unique. Each scale has tiny sharp, thin spinules. As you run your hand over the fish you can feel these scale modifications. The eyes are bulged due to the pressure change of coming up from such deep depths. The scientists determined the sex of the Grenadier and then it was frozen for future study.

TAS Karen Grady 4-13-17 grenadier

Mexican Grenadier

We also caught two Cutthroat Eels, from the family Synaphobranchidae, that were both females. Synaphobranch means unified gill… the two gill slits join together making it look like a cut throat. They are bottom-dwelling fish, found in deep waters. The eels were weighed, measured, and the scientists determined the sex and maturity of each eel. It is important that they make accurate identification of specimens and collect data. The scientists work together using personal knowledge and books when necessary. There are times on deck when the scientists will stop to examine a species and will take multiple pictures of certain identifying parts so that they can look at them closely later.

 

Personal Log

One of the great things during a watch is being able to talk with the scientists. I am an avid listener and observer. This is what they do year in and year out and they love what they do. I am a quiet observer a lot of the time. I listen and then ask questions later. It’s not exactly easy to carry around paper and pencil to take notes. But during the transit portions or soak times I ask more questions and gather information to share in my blog posts or for the lesson plan I will be writing when I get home.

The food has been great here on the ship. Our stewards have fresh salads, and menus that include two main course options, a daily soup, dessert and multiple side choices.   There are snacks available 24/7 so you are never hungry. Because the meals are so great you see most people trying to fit in a workout during the day. I have been introduced to the Jacob’s ladder for workouts. I never liked hills and now I can say I don’t like climbing ladder rungs either. That machine is evil!! However, I will continue to do cardio on it as the food is excellent and keeping food in your stomach helps prevent sea sickness. I will happily eat more than I usually do if it means I don’t get seasick. An example of a typical lunch would be today when we had choices of salad, reuben, tuna melt, french fries, sweet potato fries, cookies and several other sides.

Today started with us catching two Cutthroat Eels and a Mexican Grenadier. You can see from the pictures I have posted that they look very different from most fish that you see. They really are that color. It was a shock after the sleek sharks and the bright orange Red Snapper I had seen on previous sets. I was busy watching the scientists using their books and personal knowledge to identify each species accurately.   After we finished the work up on the fish we caught we headed for the next station. Now we are back to shallower fishing and expect to catch sharks, red snapper, and a variety of other fish.

TAS Karen Grady 4-13-17 grenadier and eels

Two cutthroat eels (top) and Mexican grenadier (bottom)

I can honestly say that the 12 hour shifts start wearing you down, and sleeping is not an issue once you climb under the covers. The waves will wake you up now and then. And some mornings I wake up and can smell them cooking breakfast but sleep overrides the smell of food because I know how long it will be till I get to bed again. Walking out on deck each morning to views like this does lead to a smile on your face, that and the music that is playing loudly on the deck. Yesterday it was Hair Nation…. taking me back to the 80’s.

TAS Karen Grady 4-13-17 blue water

View from the deck of NOAA Ship Oregon II

Did You Know?

The Gulf of Mexico is roughly 995 miles along its longer, east-west axis. It has a surface area of about 600,000 square miles.

A wide variety of physical adaptations allow sharks to thrive in the Gulf of Mexico. They have powerful smell receptors. The sensory organs lining their prominent snouts, called ampullae of Lorenzini, can detect movement of potential prey even if the sharks cannot see it. These sensory organs assist in trailing injured marine animals from great distances. They help sharks locate all sort of other things, too– shrimp boats, other sharks, birds, turtles (tiger sharks a big turtle eaters!), even boats that are dumping trash.

The skin on a shark is smooth if you run your hand head to tail and rough like sandpaper if you run your hand from tail to head. At one time, sharks skin was used as a form of sandpaper. The dermal denticles, or skin teeth, can be different from species to species and can sometimes be used as a character to look at when trying to identify one species from another.