Tawny Nurse Shark

A group of tawny nurse sharks (Nebris ferrungineus) circling each other at dusk. This behaviour may be related to reproduction, the female, top, looks heavily pregnant in this photo and the male, below, might be able to sense she is soon to give birth. Note in the background there is another group of sharks circling each other. Photo by Alexander Mustard, for more go to www.amustard.com

Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Orectolobiformes
Family: Ginglymostomatidae
Genus: Nebrius
Species: Nebrius ferrugineus

I have this kids’ picture book that illustrates 1000 things you can find in the sea, and I use it on occasion to decide what I’m going to research next. I haven’t written about a shark in a while, so I decided to research the Tawny Nurse Shark, also called Nebrius ferrugineus. Though to her friends, she’s referred to as Madame X…

I wish I was kidding about the common name Madame X . Supposedly, the common name was coined in the 1930s by a shark fisherman that found a specimen in Australian waters; before then, it had not been recorded in those areas.

The tawny nurse shark is located in the Indian Ocean, and the in western and southwestern areas of the Pacific Ocean. This shark hangs out near or on the bottom in sheltered areas, including lagoons, channels, seagrass beds, caves on the outskirts of coral reefs, crevices in coral reefs, and right off beaches. They sleep together in secluded areas during the day and hunt for prey at night.

Around the mouth, tawny nurse sharks have barbels—whisker-like appendage—that help them sense prey. They eat small fish and benthic organisms (creatures that live on the seafloor), including crustaceans, sea urchins, and some cephalopods. When it finds potential food, the shark creates a suction to pull the prey out of hiding and into its mouth, where comb-like teeth help to break up hard shells.

This is a pretty docile shark. Divers consider it a favorite because the shark allows the divers to approach it, even touch it. However, when harassed, it will fight back and has been recorded to cause non-fatal bite injuries.

Please do not touch sea creatures unless you have the specific training to do so! You would lash out too if a stranger came up and started putting their hands all over you.

Tawny nurse sharks are considered vulnerable to extinction by the IUCN Red List, and their population numbers are declining. They have a limited home range, so their immediate environment is very important to them. Some populations are declining due to overfishing of the nearby reefs. Some sharks get caught up in gill nets and die as bycatch.

Bycatch refers to any creature that isn’t the target of the catch. So if fisherman are using nets to catch tuna, then anything that isn’t tuna that gets caught up in the net is considered bycatch. Typically, bycatch is thrown back into the ocean, whether it’s alive or dead, because most fishing boats have a bycatch limit.

Tawny nurse sharks are also considered game in some countries. Their “fighting spirit” and strength make them a popular shark to fish for, especially in competitive fishing. Some areas will eat the meat of the tawny nurse shark and ship the fins to Asian countries.

If we’re not careful, this is another species of shark that can disappear before we know it, especially since it has a low reproductive rate. A balance between the fishing industry’s needs and proper fishing regulations must be found in order to address this issue.

Sources and links:
Ocean the Definitive Visual Guide made by the American Museum of Natural History
https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/nebrius-ferrugineus/ ⇐lots of information
https://www.sharks.org/tawny-nurse-shark-nebrius-ferrugineus ⇐brief overview
https://www.fishbase.de/summary/Nebrius-ferrugineus.html
https://fishesofaustralia.net.au/home/species/1974#moreinfo ⇐talks about the Australian populations
https://www.iucnredlist.org/species/41835/10576661

Whale Sharks

A circular fisheye photo of a whale shark (Rhincodon typus) gapes open its mouth while feeding at the surface, in a behaviour known as botella feeding. Photo taken by Dr. Alex Mustard, you can find more amazing photos at www.amustard.com

Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Chrondrichthyes
Order: Orectolobiformes
Family: Rhincodontidae
Genius: Rhincodon
Species: Typus

A good friend of mine from college is a huge shark enthusiast. She could tell you all sorts of facts about sharks and I’d always go to her if I was having a hard time learning various tidbits about them for class. So I hope I do the whale shark justice today, or else I’m sure I’ll get a playful smack for it later!

Whale sharks (Rhinocodon typus) are pretty cool because they’re the largest shark that lives today, which makes them the largest fish too. Sharks belong to the class of cartilaginous fish with skates and rays—yes, skates and rays are considered fish too. Whale sharks grow up to 65 ft long and are typically the size of a school bus. Their mouths are large enough to fit a person inside comfortably, but don’t worry. We’re safe from these gentle giants because they’re filter feeders! That’s right, these behemoths feed on some of the smallest organisms on the food web—plankton and small fish. But how do they get enough food to support their size?

While they cruise around the tropical waters of the oceans they open their large mouths, suck in a lot of water, and push it out over their gills where the food gets stuck on gill rakers. The food sits on the bony projections until it’s later swallowed. Other than their size, you can also identify these guys by the long ridges that run down their bodies and their spot covered skin. In fact, each Rhincodon typus has a unique pattern of white spots that allows scientists to identify different individuals.

Here’s another neat fact about whale sharks. Whale shark mothers carry their fertilized eggs inside themselves and those eggs will hatch inside her, allowing her to give birth to live young. Cool, right? Sharks have a lot of weird birthing processes that I’ll eventually cover, but this process is called ovoviviparous—that’s a mouthful!

I hope I’ve gotten you interested in whale sharks with this piece. I saw my first one a few years ago at the Georgia Aquarium in Atlanta, Georgia. I didn’t know what to expect but it was like love at first sight. They were these big goofy sharks gliding around the large tank, occasionally opening their mouths as they went. They were really peaceful to watch and that’s what I did for hours, letting the people around me melt away as I watched the whale sharks move about and the manta rays danced around them.

It’s sad to know that whale shark populations are declining, even though they’re protected in some countries. Their meat and fins are highly sought after for shark fin soup, and they are hunted in unsustainable numbers. Don’t get me started on the dish, not yet. When you get the chance, take the time to watch these gentle giants and get lost in their goofy majesty.

Sources and cool links:
Ocean: The Definitive Visual Guide made by the American Museum of Natural History
https://www.nationalgeographic.com/animals/fish/w/whale-shark/
https://www.sharksinfo.com/ovoviviparity.html
https://www.georgiaaquarium.org/?rebound=1