Anne Krauss: Tooth Truth and Tempests, September 30, 2018


NOAA Teacher at Sea

Anne Krauss

Aboard NOAA Ship Oregon II

August 12 – August 25, 2018

 

Mission: Shark/Red Snapper Longline Survey

Geographic Area of Cruise: Western North Atlantic Ocean/Gulf of Mexico

Date: September 30, 2018

Weather Data from Home

Conditions at 1515

Latitude: 43° 09’ N

Longitude: 77° 36’ W

Barometric Pressure: 1026.3 mbar

Air Temperature: 14° C

Wind Speed: S 10 km/h

Humidity: 71%

 

Science and Technology Log

My students sent me off with many shark questions before I left for the Shark/Red Snapper Longline Survey. Much of their curiosity revolved around one of the most fear-inducing features of a shark: their teeth! Students wanted to know:

Why do sharks eat fish?
How and why do sharks have so many teeth?
Why do sharks have different kinds of teeth?
Do sharks eat each other? What hunts sharks, besides other sharks?
And one of my favorite student questions: Why do sharks eat regular people, but not scientists?

Most people think of sharks as stalking, stealthy, steel-grey hunters. With a variety of colors, patterns, fin shapes, and body designs, sharks do not look the same. They do not eat the same things, or even get their food the same way. Instead, they employ a variety of feeding strategies. Some gentle giants, like the whale shark (Rhincodon typus), are filter feeders. They strain tiny plants and animals, as well as small fish, from the water. Others, such as the angel shark (Squatina spp.), rely on their flattened bodies, camouflage, and the lightning-fast element of surprise. Instead of actively pursuing their prey, they wait for food to come to them and ambush their meal. These suction-feeding sharks have tiny, pointed, rearward-facing teeth to trap the prey that has been sucked into the shark’s mouth. This video demonstrates how the angel shark uses clever camouflaging and special adaptations to get a meal:

https://www.nationalgeographic.com.au/videos/shark-kill-zone/angel-shark-stealth-2838.aspx

A circle hook is held up against the sky. The horizon is in the background.

Circle hooks are used in longline fishing. Each hook is baited with mackerel (Scomber scombrus).

A pile of frozen mackerel used as bait.

Frozen mackerel (Scomber scombrus) is used as bait.

Circle hooks are placed along the edges of plastic barrels. The hooks are connected to thick, plastic fishing line called monofilament.

The circle hooks and gangions are stored in barrels. The hooks are attached to thick, plastic fishing line called monofilament.

100 circle hooks baited with mackerel. The baited hooks are placed on the edges of barrels, which are sitting on deck.

All 100 circle hooks were baited with mackerel, but sharks also eat a variety of other fish.

The sharks we caught through longline fishing methods were attracted to the Atlantic mackerel (Scomber scombrus) that we used as bait. Depending on the species of shark and its diet, shark teeth can come in dozens of different shapes and sizes. Instead of just two sets of teeth like we have, a shark has many rows of teeth. Each series is known as a tooth file. As its teeth fall out, the shark will continually grow and replace teeth throughout its lifetime—a “conveyor belt” of new teeth. Some sharks have 5 rows of teeth, while the bull shark (Carcharhinus leucas) may have as many as 50 rows of teeth!

The sandbar shark (Carcharhinus plumbeus) usually has about 14 rows of teeth. They may lose teeth every ten days or so, and most sharks typically lose at least one tooth a week. Why? Their teeth may get stuck in their prey, which can be tough and bony. When you don’t have hands, and need to explore the world with your mouth, it’s easy to lose or break a tooth now and then. Throughout its lifetime, a shark may go through over 30,000 teeth. The shark tooth fairy must be very busy!

A sandbar shark (Carcharhinus plumbeus) tooth with serrated edges.

Sandbar shark (Carcharhinus plumbeus) tooth. The sandbar shark is distinguishable by its tall, triangular first dorsal fin. Sharks’ teeth are equally as hard as human teeth, but they are not attached to the gums by a root, like human teeth. Image credit: Apex Predators Program, NEFSC/NOAA

Similar to our dining utensils, sharks’ teeth are designed for cutting, spearing, and/or crushing. The tooth shape depends upon the shark’s diet. Sharks’ teeth are not uniform (exactly the same), so the size and shape of the teeth vary, depending on their location in the upper and lower jaws. Some sharks have long, angled, and pointed teeth for piercing and spearing their food. Similar to a fork, this ensures that their slippery meals don’t escape. Other sharks and rays have strong, flattened teeth for crushing the hard shells of their prey. These teeth work like a nutcracker or shellfish-cracking tool. Still others, like the famously fierce-looking teeth of the great white, are triangular and serrated. Like a steak knife, these teeth are used for tearing, sawing, and cutting into their prey.

A shortfin mako shark (Isurus oxyrinchus) tooth is narrow and pointed.

A shortfin mako shark (Isurus oxyrinchus) tooth is narrow and pointed. Image credit: Apex Predators Program, NEFSC/NOAA

Smooth dogfish (Mustelus canis) teeth are flattened for crushing prey.

Smooth dogfish (Mustelus canis) teeth are flattened for crushing prey. Image credit: Apex Predators Program, NEFSC/NOAA

A silky shark (Carcharhinus falciformis) tooth has serrated edges.

A silky shark (Carcharhinus falciformis) tooth has serrated edges. Image credit: Apex Predators Program, NEFSC/NOAA

A tiger shark (Galeocerdo cuvier) tooth is jagged and serrated.

A tiger shark (Galeocerdo cuvier) tooth is jagged and serrated. Image credit: Apex Predators Program, NEFSC/NOAA

Link to more shark tooth images: https://www.nefsc.noaa.gov/rcb/photogallery/shark_teeth.html

Beyond their teeth, other body features contribute to a shark’s ability to bite, crush, pursue, or ambush their prey. The powerful muscles that control their jaws and swimming ability, the position of their mouth, and the shape of their caudal (tail) fin all influence how a shark gets its food. Unlike humans, sharks do not chew their food. They swallow their food whole, or use their teeth to rip, shred, crush, and tear their food into smaller chunks that the shark can swallow. No need to floss or brush after a meal: sharks’ teeth contain fluoride, which helps to prevent cavities and decay.

Some people may find it hard to swallow the idea that sharks aren’t mindless menaces, but shark encounters are quite rare. Sharks have many extraordinary adaptations that make them efficient swimmers and hunters of other marine life, not humans. Whenever sharks come up in conversation, I am careful to dispel myths about these captivating creatures, trying to replace fear with facts (and hopefully, curiosity and respect). Since sharks can’t talk, I’m happy to advocate for them. Despite the way sharks are negatively portrayed in the media, I assure my students that sharks far prefer to eat bony fish, smaller sharks, skates, rays, octopus, squid, bivalves, crustaceans, marine mammals, plankton, and other marine life over humans. Instead of fear, I try to instill awareness of the vital role sharks fulfill in the ecosystem. We are a far greater threat to them, and they require our respect and protection.

For more information on sharks: https://oceanservice.noaa.gov/facts/sharkseat.html

 

Personal Log

As storms and hurricanes tear across the Gulf of Mexico, causing destruction and devastation, my thoughts are with the impacted areas. Before my Teacher at Sea placement, I never thought I’d spend time in the region, so it’s interesting to see now-familiar locations on the news and weather maps. One of my favorite aspects of being at sea was watching the sky: recognizing constellations while fishing at night, gazing at glorious, melting sunsets, and observing storm clouds gathering in the distance. The colors and clouds were ever-changing, a reminder of the dynamic power of nature.

A colorful sunset on the Gulf of Mexico.

The sky was vibrant.

Storm clouds gather over Tampa, Florida.

Storm clouds gathered over Tampa, Florida.

Darkening clouds over the water.

The clouds clustered around Tampa. The city looked very small on the horizon.

Darkening clouds over the water.

As the rain started, the clouds darkened.

Darkening clouds over the water.

The colors changed and darkened as lightning started in the distance.

Darkening clouds over the water.

Dramatic dark clouds and lightning.

Watching the recent storm coverage on TV reinforced the importance of strong and accurate communication skills. Similar to a sidebar on the page, much of the supplementary storm information was printed on the screen. For someone who needed to evacuate quickly or was worried about loved ones in the area, this printed information could be crucial. As I listened to the reporters’ updates on the storm damage, aware that they were most likely reading from scripted notes, I was reminded of the challenge of conveying complex science through everyday language.

Two maps show the Gulf of Mexico.

The top image from Google Maps shows one research station where we were longline fishing in August (marked in red). The bottom satellite image shows Hurricane Michael moving through the same area. Image credits: Map of the Gulf of Mexico. Google Maps, 17 August 2018, maps.google.com; satellite image: NOAA via Associated Press.

One might assume that a typical day at sea only focused on science, technology, and math. In fact, all school subjects surfaced at some point in my experience at sea. For example, an understanding of geography helped me to understand where we were sailing and how our location influenced the type of wildlife we were seeing. People who were more familiar with the Gulf of Mexico shared some facts about the cultural, economic, and historical significance of certain locations, shedding light on our relationship with water.

Fishing is an old practice steeped in tradition, but throughout the ship, modern navigation equipment made it possible to fish more efficiently by plotting our locations while avoiding hazards such as natural formations and other vessels. Feats of engineering provided speed, power, drinkable water, and technological conveniences such as GPS, air conditioning, and Wi-Fi. In contrast to the natural evolution of sharks, these artificial adaptations provided many advantages at sea. To utilize the modern technology, however, literacy was required to input data and interpret the information on the dozens of monitors on board. Literacy and strong communication skills were required to understand and convey data to others. Reading and critical thinking allowed us to interpret maps and data, understand charts and graphs, and access news articles about the red tide we encountered.

I witnessed almost every person on board applying literacy skills throughout their day. Whether they were reading and understanding crucial written communication, reading instructions, selecting a dinner option from the menu, or referencing a field guide, they were applying reading strategies. In the offices and work spaces on board, there was no shortage of instructional manuals, safe operating procedures, informational binders, or wildlife field guides.

Writing helped to organize important tasks and schedules. To manage and organize daily tasks and responsibilities, many people utilized sticky notes and checklists. Computer and typing skills were also important. Some people were inputting data, writing research papers and projects, sharing their work through social media, or simply responding to work-related emails. The dive operation that I observed started as a thoroughly written dive plan. All of these tasks required clear and accurate written communication.

Junior Unlicensed Engineer (JUE) Jack Standfast holds a small notebook used for recording daily tasks and responsibilities.

Junior Unlicensed Engineer (JUE) Jack Standfast carried a small notebook in his pocket, recording the various engineering tasks he’d completed throughout the day.

Each day, I saw real-life examples of the strong ties between science and language arts. Recording accurate scientific data required measurement, weight, and observational skills, but literacy was required to read and interpret the data recording sheets. Neat handwriting and careful letter spacing were important for recording accurate data, reinforcing why we practice these skills in school. To ensure that a species was correctly identified and recorded, spelling could be an important factor. Throughout the experience, writing was essential for taking interview notes and brainstorming blog ideas, as well as following the writing process for my blog posts. If I had any energy left at the end of my day (usually around 2:00 AM), I consulted one of my shark field guides to read more about the intriguing species we saw.

 

Did You Know?

No need for a teething ring: Sharks begin shedding their teeth before they are even born. Shark pups (baby sharks) are born with complete sets of teeth. Sharks aren’t mammals, so they don’t rely upon their mothers for food after they’re born. They swim away and must fend for themselves, so those born-to-bite teeth come in handy.

Recommended Reading

Smart About Sharks written and illustrated by Owen Davey

Appropriate for older readers, the clever, comprehensive text offers interesting facts, tidbits, and trivia. The book dives a bit deeper to go beyond basic shark facts and knowledge. I’ve read hundreds of shark books, and I appreciated learning something new. The text doesn’t shy away from scientific terminology and concepts, such as phylogeny (eight orders of sharks and representative species). The facts reflect recent research findings on shark behavior. Lesser-known species are included, highlighting the diversity in body shapes, sizes, and specialized features. From a design standpoint, the aesthetically appealing illustrations are stylized, colorful, and engaging. Simple infographics provide explanations of complex ideas. Fact meets fiction in a section about shark mythology from around the world. The book concludes with a discussion of threats to sharks, as well as ocean conservation tips.

The cover of Smart About Sharks by Owen Davey.

Smart About Sharks written and illustrated by Owen Davey; published by Flying Eye Books, New York, 2016

 

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