Eelgrass

For a little underwater plant, eelgrass does a whole lot of good. These submerged meadows anchor the mud and silt to the bottom, keeping the surrounding waters clear. That means a whole host of aquatic life can thrive there. But problems caused by too many nutrients in the water and other manmade issues have recently caused a decline in the size of eelgrass beds.

In this Untamed Science video, Jonas visits with Dr. Eduardo Infantes from the University of Gothenburg in Sweden. Together they take a look at the threats to aquatic plants and restoration efforts underway to save Zostera marina, or eelgrass.

Eelgrass: What it is, how it works, and why we need it.

Eelgrass, sometimes called subaquatic vegetation (SAV), is about a quarter inch wide (.63cm) and up to three feet (91cm) long. It grows in water that can be about three to nine feet deep (1m to 3m). Eelgrass is always submerged, and its roots, called rhizomes, anchor the plant to the bottom. Like many land-based grasses, eelgrass multiplies by producing hundreds of seeds in the spring and summer, which float in the current before gradually being carried to the bottom.

Just as trees and shrubs keep soil from eroding on land, the rhizomes keep silt and mud in place underwater. “If there was no eelgrass, we would really lose our water clarity because there would be more silt in suspension,” said Dr. Infantes. “Eelgrass originally came from the land and established itself in the marine ecosystem.”

Eelgrass beds play a variety of roles in the aquatic ecosystem. For some animals, the beds are a source of food. For others, the dense vegetation forms a safe place for newly hatched life to hide, acting like an underwater nursery. Flounder, shellfish, and crabs all use eelgrass at some point in their lives. Without eelgrass beds, that sea life would be reduced or even disappear.

Trouble in Paradise: It’s not you; it’s me.

Unfortunately, eelgrass beds are under threat around the world. According to the National Oceanographic and Atmospheric Association (NOAA), 65% of U.S. estuaries and coastal waters are damaged, and those threats come from a variety of sources: boat propellers can grind up the bottom; dredging for shellfish uses toothed rakes and tears up the beds. But the most important threat comes from a process called eutrophication.

Eutrophication is caused by a variety of activities, but the biggest contributors are excess amounts of phosphorus and nitrogen working their way into the water. Burning fossil fuels creates phosphorus in the atmosphere, which eventually is deposited into water systems. In addition, farms and homes at the water’s edge that use fertilizers contribute to increased nitrogen levels when rain washes excess fertilizers into coastal waters.

The same fertilizers that encourage plant growth on land can wreak havoc with algae growth in the water. Dense mats of algae called algal blooms can form, blocking vital sunlight from reaching the eelgrass beds. Once the algae spreads, it also begins to die off. Algae decay consumes most, if not all the oxygen in the water, creating a dead zone called hypoxia. At that point, the eelgrass bed dies and the aquatic life that relies on those beds go with it. Plus, the mud that is no longer held in place by the rhizomes would become suspended in the water, making it difficult for eelgrass to reestablish itself.

NOAA also says that eutrophication can cause ocean acidification. That means fish and shellfish growth slows down, reducing the catch of commercial and recreational fisheries.

Hope on the Horizon

While the issue of eelgrass bed destruction is concerning, efforts are being made to curb the flow of nutrients into the water using purification systems and buffers between farms and the water. Drone photography allows scientists to map areas where eelgrass meadows grow to measure their increase or decrease, and to better recognize which areas need protection.

Recent experiments in Connecticut have shown that oyster aquaculture may also play a part in nutrient reduction. One study showed that the natural process of filtration feeding that takes place in oysters may remove as many nutrients as comparable wastewater improvements costing hundreds of millions of dollars.

All of this is good news for scientists like Dr. Infantes. He’s now working to restore eelgrass beds on the coast of Sweden. In some cases that involves gathering the seeds from existing eelgrass beds and planting them elsewhere. In others, seeds are brought to his laboratory for starting. The new growths are later returned to the water, attached to anchors to prevent them from drifting away. It’s a process that encourages Infantes.

“When you lose a forest, you want to recover the forest. So here we have loss of the meadows, and we want to recover the meadows.”

Coral Catshark

The name “coral catshark” might make you imagine a fluffy little creature. But the coral catshark (Atelomycterus marmoratus) doesn’t look anything like a cat. In fact, it doesn’t even look much like a shark—more like a colorful snake or eel.

Nevertheless, this little shark is quite adorable. That’s probably why you’re more likely to see it in an aquarium than in the wild. In fact, this shark has such a limited range and is so secretive that scientists really don’t know much about them or their biology.

Where do coral catsharks live, and what do they look like?

Coral catsharks live in the western Indian Ocean, from India to New Guinea. These shy sharks with cat-like eyes live in shallow water around coral reefs—hence, the name. They love to hang out in nooks and crannies on the reef, and their long, tube-like bodies help them slip into these cracks. With a body length of merely 1 ½ to 2 ½ feet, they can fit into a lot of small spaces!

Coral catsharks, like wobbegong sharks, are incredibly well-camouflaged for reef life. They have grayish bodies with a background pattern of black and white spots and bars. They almost look like midget versions of leopard sharks.

How are coral catshark populations doing?

The IUCN has classified coral catsharks as a “Near Threatened” species, but the truth is there aren’t accurate estimates of the population as a whole. This is probably because the coral catshark isn’t a very important economic species—it’s too small to eat, it’s not the highlight of a tourism trip, and because it’s in southeast Asia, it’s far away from many concerted conservation efforts.

According to the IUCN’s best guess, there might be some serious threats to wild coral catshark populations, however. Their coral reef habitat is being lost due to coral mining for building materials (yep—buildings made of coral).

And while people don’t really seek them out as food, they still are being victimized by fishing—in particular, dynamite fishing, which is a common practice where the coral catsharks live (why not a little extra gunpowder with your fish dinner?).

Coral Catsharks and the Aquarium Trade

The coral catshark is a very popular shark for home aquaria. It’s supposedly easy to keep (i.e., difficult to kill) and has even reproduced in home aquaria, which is probably a good sign they’re comfortable in their environment. Plus, they’re one of the smallest shark species around, so it’s possible to keep these sharks in very large aquariums for their entire lives (some aquarists only keep the small juvenile versions of some shark species and release them into the ocean when they get bigger—not a good practice).

It’s possible that the trade in live coral catsharks can be contributing to conservation concerns for wild populations, but because so little is known about these sharks, we can’t really say. This is yet another instance where we need more research done so we can conserve these sharks well into the future.

Caribbean Reef Shark

Imagine going on a beautiful Caribbean vacation and taking a snorkeling adventure. You’re swimming along a beautiful reef full of colorful fish. Suddenly, out of nowhere, a huge gray and white shark shows up beside you. Before you hit the panic button, take a second to breathe. It’s very likely a Caribbean reef shark.

These large sharks are the most common type of sharks you’ll find cruising along a reef, and they’re mostly harmless. An encounter can be a bit scary since they do sort of look like Great White sharks to the untrained eye, but these sharks have more to teach you than you have need to fear them.

Where can you find Caribbean reef sharks?

Caribbean reef sharks are found exclusively in the Western Atlantic Ocean, from North Carolina down to Brazil. They are one of the most common shark species in the Caribbean Sea.

These interesting sharks prefer to swim near the bottom of reefs, which is why it’s so common for them to interact with people. After all, we enjoy a nice colorful reef tour, too! These sharks don’t venture out too far into open water, like mako sharks or porbeagle sharks, so it’s unlikely you’ll see them from your cruise ship as you travel from one port to another.

How do Caribbean reef sharks reproduce?

Since Caribbean reef sharks are so plentiful and common, you’d expect that they’d have a high reproductive rate and pop out shark pups like little pinballs. But in fact, these sharks have a very low reproductive rate, especially compared to some prolific species like leopard sharks.

Female Caribbean reef sharks will only give birth every two years, and only to a small litter of three to six pups. What’s fascinating about Caribbean reef sharks is that they reproduce through placental viviparity. This just means that the pups are attached to their moms via a placenta while she’s pregnant with them—just like mammals!

Are Caribbean reef sharks dangerous?

Although Caribbean reef sharks are large and do have the potential to injure people, they’re generally not considered dangerous.

In fact, according to the International Shark Attack File, only four unprovoked attacks from this species have ever occurred on humans, and none of them were fatal (although it was certainly a bad day for the shark bite victims). This is especially impressive, considering that Caribbean reef sharks are one of the most common large sharks that people encounter while in the ocean.

Instead of people, Caribbean reef sharks cruise the bottoms of reefs looking for dead, dying, or sick fish. They’re more like the vacuum cleaners of the reefs than aggressive human-hunters.

What are the threats to Caribbean reef shark populations?

There are many potential threats to Caribbean reef sharks. They are heavily targeted by humans because they’re so common, and they are very valuable to fisherman.

Every single body part of the Caribbean reef shark can be used. Its jaws can be used as ornaments (ever seen a set of shark jaws hanging up in a sushi restaurant?); its liver is used for oil; its fins and meat are used for food; and its skin can even be made into leather. The remainder of the shark’s body can be ground into fishmeal to be used in gardens as fertilizer or as animal feed.

Additionally, Caribbean reef sharks are also commonly caught as bycatch by fishermen. After all, they are fish-eaters and do hang out where the fish tend to be.

How can I see Caribbean reef sharks in the wild?

If you’re diving on a reef full of fishes in the Caribbean, there’s a good chance you’ll see a Caribbean reef shark out of the corner of your eye. Some tour operators even hold shark-feeding tours for the adventurous tourist diver. These are illegal in the U.S. but are quite popular in the Bahamas and other island nations. Here’s a video showing what these tours look like:

These shark-feeding tours are controversial. There’s a lot of pros to them. They provide a great source of revenue for tour operators and give them an incentive to help the sharks, rather than harvest them indiscriminately. They also help make everyday people more aware and interested in sharks, and less afraid of them. That’s a huge positive, because a fear of sharks can hurt conservation efforts.

But critics say it’s ethically wrong to feed wildlife. It’s possible that these shark-feeding tours can train sharks to associate people with food. This is exactly what happened with brown bears in Yellowstone National Park in the early 1900s when park officials allowed bears to eat out of landfills, providing people with good (albeit messy) photo opportunities.

Finally, it’s also possible that the Caribbean reef sharks will tend to stay in a particular location if they know they’ll be fed there. That could allow fisherman to target them even more heavily (wouldn’t you want to go to the good “fishing hole”?).

So far, the jury is still out on whether shark-feeding operations are beneficial or not. But one thing’s for sure: the more people showing positive interest in these amazing creatures, the better.

Salmon Shark

You might think you wouldn’t stand a chance of seeing any big sharks if you’re far north in the Pacific. After all, big sharks live in warmer waters around places like Hawaii, Australia, and California, right?

Wrong. In fact, the north Pacific is home to plenty of large sharks. One of the most common is the salmon shark (Lamna ditropis) named after its favorite prey—you guessed it—salmon.

What do salmon sharks look like?

The salmon shark is the doppelganger of the porbeagle shark (Lamna nasus). They look almost identical, growing up to 12 feet long with a dark grayish back and a lighter underbelly. While the porbeagle hangs out in the north Atlantic, the salmon shark prefers the cool waters of the north Pacific.

It’s likely that these shark species evolved from the same ancestor. Whereas one population ended up on one side of the Americas, another population ended up on the other side. Since they are unlikely to swim through warm waters to reach the other side of the continents and intermix, they have stayed separate and diverged into two distinct (but very similar) species.

Where do salmon sharks live?

You can come across salmon sharks almost anywhere in the north Pacific, whether you’re close to shore or out in the open ocean.

Salmon sharks show an interesting pattern in sexual segregation (i.e., males and females form separate groups). The further north you go, the more the two sexes stay away from each other. Females hang out more in the northeastern Pacific, while males swim around in the northwestern Pacific.

How do salmon sharks reproduce?

When it comes to reproduction, salmon sharks have a similar gestation period to humans: nine months. Breeding takes place around August and September, so pups are born in spring and early summer. A female salmon shark can breed about every two years.

That’s where the similarities end though. Salmon sharks reproduce via aplacental viviparity. After breeding, a female will carry a bunch of fertilized eggs in her uterus. After hatching in utero, the biggest pups will actually eat their fellow siblings until just two to five pups remain. (It gives a whole new meaning to sibling rivalry!) Surviving pups are born fully-formed and ready to live on their own.

What do salmon sharks eat?

Salmon sharks do indeed eat a lot of salmon. According to the Alaska Department of Fish and Game, in 1998 salmon sharks were responsible for eating up to a full quarter of the annual run of salmon in Prince William Sound!

When they’re not chowing down on salmon, however, they’re like most sharks and will eat basically anything that can fit into their mouth. There are no official recorded attacks on humans by salmon sharks, but theoretically it is possible because they are so large. But don’t let that scare you—check out the video of people swimming with salmon sharks below:

Salmon Sharks: Masters of Countercurrent Heat Exchange

Sharks are generally considered ectothermic, meaning that they are cold-blooded and take on the same temperature as the surrounding environment. That poses a problem for salmon sharks that swim around in the super-chilly water at the high latitudes they prefer. So, they’ve come up with a solution: they’re partially endothermic, a trait that allows them to heat up their body to a certain degree!

The way salmon sharks do this is with countercurrent heat exchangers. (It sounds more like a high-tech racing car feature than shark trait.) This feature manages the animal’s body heat using blood vessels laid out in a specific pattern.

Blood coming from the shark’s exterior vessels is very cold, since it’s been right next to the chilly water. Blood coming from the shark’s inner body is usually a bit warmer, since it has been warmed by the muscles. In salmon sharks, the cold blood vessels coming from the exterior are laid out next to the warm blood vessels coming from the muscles. This heats up the incoming blood. (Kind of how department stores manage in the winter: you walk through the doors and receive a blast of hot air to warm you–and the air coming in with you–fast.)

This special trick is what gives salmon sharks (and their porbeagle doppelgangers) an edge over their prey. Warm muscles (up to 20ºF warmer than the surrounding water) allow them to swim just a bit faster than the icy salmon, so they’re able to chomp them up like a ruthless, finned Pac-Man.

How are salmon shark populations doing?

The status of salmon sharks is one of the happier conservation stories in the shark world. They’re not widely sought after by commercial or sport fishermen, except for a very small sport fishery in Alaska. They are caught as bycatch by commercial fisheries, but studies have shown that their populations are stable, so fishing doesn’t seem to be especially detrimental.

Even though the news is good now, these amazing sharks will always require monitoring. They are slow-growing and give birth to just a few pups at a time, so it would be easy for salmon sharks to become vulnerable in the future if their populations did decline. But for now, we can rest easy that these cool creatures are doing just fine.

Pacific Sleeper Shark

Imagine you’re out on a fishing charter boat, trolling for deep-water fish like halibut or rockfish. You catch something on the line and reel it in excitedly. It takes a long time coming up from so deep, and you can tell it’s a big one.

You see a shape materializing under your boat. As it gets closer, it turns into a long, inky black blob—not quite the fish you were expecting.

Could it be Cthulhu rising? Thankfully, not quite. It just might be a Pacific sleeper shark (Somniosus pacificus) that you aroused from its slow crawl in the depths of the Pacific.

The Pacific sleeper shark is related to the famous Greenland shark (Somniosus microcephalus), but beyond that and a few other facts, very little is known about this mysterious shark.

What does a Pacific sleeper shark look like?

Pacific sleeper sharks aren’t your everyday silver-and-white, streamlined predator. They have a long, torpedo-shaped body with a wide, blunt head and a relatively small mouth. They can reach up to 22 feet in length, but most Pacific sleeper sharks don’t extend beyond the mid-teens.

Unlike most sharks, they are the same color all over—a deep grayish-black that allows them to better blend in with the inky blackness where they prefer to live. They have a short, small dorsal fin and a long, sweeping caudal (tail) fin.

Pacific sleeper sharks have very small eyes. It’s a good thing they rely on their sense of smell to find prey, because many Pacific sleeper sharks’ eyes are actually colonized by a special parasite, Ommatokoita elongata. These nightmare-inducing little beasts burrow into the cornea (outer layer) of a shark’s eye, where they feast on the tissue. Sharks with this parasite are nearly blind.

Where do Pacific sleeper sharks live?

Pacific sleeper sharks live in…you guessed it…the Pacific Ocean! In fact, they are the Pacific equivalent of the Greenland shark that lives in the Atlantic Ocean.

People used to think that Pacific sleeper sharks were a far-north species because that’s the only place they would see them. In fact, they may even come right up to the surface of the water in the Arctic where the water is cold all throughout the entire water column.

However, people have also discovered that this gigantic shark has a much more southerly range, meandering as far west as Taiwan and east to Mexico. At these latitudes, the Pacific sleeper shark prefers to stay far down where it’s colder, often a mile or more under the sea.

Coping with the Deep, Salty Sea

At these significant depths, the sharks have developed some special physiological coping mechanisms. More urea is able to permeate its tissues, allowing it to cope with the osmotic pressure from the increasingly-salty water. Without this adaptation, it would likely shrivel up and die. For a cool demonstration of what might happen to a shark if it’s not in osmotic balance, check out this egg osmosis experiment.

Urea helps keep the shark’s tissues in osmotic balance with its saltier environment, but it comes with a drawback: it destabilizes proteins, which are the building blocks of the entire body. To counteract this effect, the shark produces another protein-stabilizing chemical: trimethylamine oxide (TMAO).

The deeper the shark lives, the more urea it needs, thus the more TMAO it develops. People who eat the meat of animals with high concentrations of this chemical experience an interesting side effect: because it is toxic, it makes them stone-drunk. While there isn’t a widely-documented history of people eating Pacific sleeper shark meat, it has caused serious problems in people who eat Greenland shark meat without proper preparation.

What do Pacific sleeper sharks eat?

If the tiger shark is considered “the Ocean’s Garbage Can,” Pacific sleeper sharks are similarly the garbage disposals of the deep. They’ll eat anything that happens to float to the bottom of the ocean and cross their path.

Surprisingly, they’re also very effective predators. Their dark skin acts like camouflage, and their bodies are especially designed for slow, easy cruising. It’s actually quite easy for them to sneak up on prey. Before their prey even knows they’re there, they’ve swung open their jaws to suck the prey in, much like a wobbegong does. Pacific sleeper sharks will eat all kinds of fish and cephalopods this way, even fast-moving top-swimming fish like salmon.

What are the threats to Pacific sleeper shark conservation?

The biggest threat to keeping these guys around is that we just don’t know much about them. Commercial fisherman have been finding more of them as bycatch in recent decades, however scientists aren’t sure if that really means their populations are increasing in size, or if fisherman are just getting better at catching them. The answer is unknown because no population studies exist on these interesting fish.

It’s difficult to study animals that live such a reclusive lifestyle because it’s hard to reach them at such deep depths. Furthermore, people don’t eat or use these sharks, so there isn’t much economic incentive to learn more about them, as with school sharks or porbeagle sharks. But maybe you can become the shark biologist that shines a light on the mysteries of the Pacific sleeper shark and gets everyone else interested in them too!

School Shark

Have you ever heard of the school shark? If not, maybe you know it by another name. Do tope shark, snapper shark, or whithound ring a bell? The names soupfin shark, oil shark, and vitamin shark give a hint about its importance to people.

The school shark has many common names but only one scientific name—Galeorhinus galeus. This is an excellent example of why scientists use scientific names, classifying each distinct species by a single official moniker. Otherwise, how would scientists in different areas know they’re talking about the same shark?

Confusing as its list of nicknames may be, the school shark has an interesting history that continues to play out to this day. Read on to learn more about this fun and fascinating shark!

What do school sharks look like?

At first glance, the school shark looks like a lot of other sharks. It’s dark grayish-blue on top, and white underneath. Look closer, though, and you’ll see the differences.

The school shark is long and slender. In fact, its snout sticks out much farther than on most sharks. It also has an odd-shaped caudal fin (tail). The top half is much larger and longer than the small bottom half, and it also has a distinct notch in it.

They have very large, almond-shaped eyes (all the better to see prey with), but don’t worry: humans aren’t on the menu. These sharks only grow to a maximum of 6.5 feet in length, and in many parts of its range, they don’t even get that big. They’re much too small to eat you!

If you see one school shark, chances are you’ll see a few more, because surprise: the school shark likes to…well…form schools (bet you didn’t see that one coming). They tend to form schools that are segregated by size and gender, somewhat like high-school cliques. While it seems like a cute trait, this can come back to haunt them, as we’ll see later.

Where do school sharks live?

Part of the reason school sharks have so many different common names is because they’re found all over the world, with only a few exceptions, like the northwest Pacific and the northwest Atlantic.

They tend to hang out around the coast rather than the open ocean, like the mako shark or the whale shark. This makes it easier for people to catch them—and catch a lot of them they do. School sharks are harvested anywhere they’re found, which is another reason why there are so many names: each culture and region has developed their own name for this commonly-caught shark.

Life as a School Shark

School sharks aren’t one to swim up to you to say hi (unlike a playful porbeagle, maybe). They prefer it a bit on the shadier side, so they tend to hang out just off the bottom of the ocean where they can eat bottom-dwelling fish, crustaceans, and molluscs (although they will travel higher to feed if there’s a tasty buffet up there).

Like a class of kids on a field trip, each school shark is also migratory with its school. Schools of school sharks can migrate hundreds of miles, and where they go varies based on what region they’re in. For example, school sharks caught in UK waters have been recaptured in northern Iceland, and school sharks are known to bounce between Australia and New Zealand.

Female school sharks reach sexual maturity between ages 10-15, and will live for a long time: up to 60 years. Females are ovoviviparous, which means they will hatch little pups within themselves before giving birth to litters of up to 52 live pups. The bigger the female, the more pups she will have. Depending on where the momma shark lives and how many nutrients she can get, she can give birth every year, every other year, or once every three years.

School Shark Conservation Concerns

Life is tough as a school shark. Everywhere they go they are targeted by humans in recreational and commercial fisheries. They are often intentionally targeted or unintentionally caught in gillnet fisheries and trawling operations.

Remember how they like to form segregated schools based on different sizes and sexes? That makes them more vulnerable to overfishing. All it takes is a bunch of well-timed passes by fishing boats to scoop out a large chunk of breeding-age females, for example. Without those females, the population growth will slow, decline, or even stop.

What’s worse, there are no harvest regulations in virtually all of its range. Even in parts where there are harvest restrictions, there have been few studies done to actually count the school shark population. That makes it tough to say how many sharks really are out there, and if current management is enough to protect them.

Australia, New Zealand, and California are among the only regions that have taken any action to protect school sharks. These efforts include closing the season during vulnerable times of the year for school sharks (such as when females are giving birth), and regulating the sizes of gillnets to catch only certain sizes of sharks.

Because of the dire situation and lack of knowledge of school sharks, the IUCN has classified these interesting fish as Vulnerable. Only time will tell whether these sharks persist in the future. In the meantime, it’s likely that some populations will become extirpated (extinct in a certain location, but not worldwide). If governments are willing to get on board with managing school shark populations in the future, we can prevent them from going extinct completely.

Leopard Shark

With a name like “leopard shark,” (Triakis semifasciata) you might think that these animals would be fearsome brutes. Many people are afraid of bull sharks and tiger sharks, after all. Don’t let the name fool you though—these pint-sized beauties actually pose almost no danger to people, even if they might mistake you for a snack.

Instead, these are one of the most common shark species you’re likely to come across if you live on the West coast of North America. Seeing them would be a real treat. Read on for more fun facts about leopard sharks!

Leopard Sharks: The Gems of The Shark World

Leopard sharks are one of the prettiest shark species you might meet. They’re a small species (especially compared to more familiar sharks like the whale shark or the Great White shark), reaching a maximum of seven feet long from tip of the snout to the tail. Most sharks of this species, however, aren’t longer than five or six feet.

Leopard sharks have a very long, narrow body with a flattened head. They have an odd-shaped tail, with the top part being much longer than the bottom part.

They are gray in color, but all along the back are dark grayish-black saddles that fade into smaller dots as you move towards the belly. The middles of these dots and saddles are lighter in color, much like how a leopard’s spots are lighter in the middle.

Where can you find leopard sharks?

If you live on the West coast of North America—anywhere between Washington and Mexico—there’s a good chance that there are tens or hundreds of leopard sharks swimming somewhere near you right now.

Leopard sharks prefer shallower waters than their open-ocean brethren (like the mako shark or whale shark). They love cruising around kelp forests, and will even come in and out with the tide, searching for tasty morsels like crabs, small fish, and even clam siphons sticking up above the ocean floor. Small leopard sharks can be found in as little as a foot of water, so don’t be surprised if you come across one while wading!

Leopard sharks often form schools with other leopard sharks and even other shark species of similar size (if they’re too small, they might become a snack!). They tend to stay put in whatever region they’re born in, although every now and then a spritely leopard shark will feel a bit adventurous and head off to a new location up to several hundred miles away. But in general, their staying put makes it easier for biologists to track and manage these sharks because they aren’t constantly flip-flopping between different countries with different management rules.

Where do baby leopard sharks come from?

Sharks are generally slow breeders, and leopard sharks fit that bill—sort of. It takes between 10 and 15 years for a female leopard shark to reach sexual maturity, and they only live for a maximum of 25-30 years anyway. They spend up to half their life just getting ready to breed.

But get ready—once they start breeding, they can really crank pups out! Female leopard sharks will give birth from anywhere between seven and 36 pups every year. They even have been known to spend time in warmer waters that help speed up pup development in utero. (Imagine if people could just spend all day in a hot yoga room and give birth in eight months instead of nine!)

Female leopard sharks give birth to their fully-formed pups in shallow waters known as nurseries, safe from predators. After dropping off their pups at the nursery, they head right back out to breed and get busy making the next generation of pups.

What are the main threats to leopard sharks?

Luckily, leopard sharks are a conservation success story. Their homebody habits, huge litters of pups, high population sizes, and limited human harvesting make them a species of Least Concern by the IUCN.

Still, there are a few potential threats that we need to watch out for to ensure leopard shark populations stay strong. The biggest one is probably recreational leopard shark fishing. These are popular sharks to catch because of their close proximity to shore, unique coloration, and tasty flesh. Fisherman in California harvest more leopard sharks than anywhere else, and in 1992 the California Department of Fish and Wildlife instituted harvest limits that have since allowed the low leopard shark populations to rebound with complete success.

Some by-catch of leopard sharks in commercial fisheries also occurs, however this isn’t considered as large a concern. Surprisingly, little leopard sharks are also targets for another unique fishery—the aquarium trade. Baby leopard sharks can fit inside large aquariums, and they make popular pets because they survive easily in an aquarium environment (at least, more easily than other species), and again, because they’re so unique-looking and easy to catch.

Finally, leopard sharks can be vulnerable to changes in local water conditions. Remember how they don’t move around much? Sometimes that habit can come back to bite them. There have been several large leopard shark die-offs due to eutrophication: when nutrients (probably from agricultural fertilizer) flow into bays, they cause algal blooms that suck up all the oxygen in the water, essentially suffocating the sharks. Even as recently as May 2017, San Francisco Bay itself has seen large leopard shark die-offs, likely from a mysterious brain fungal infection.

Although these scenarios sound scary, rest assured that right now the entire leopard shark population is doing just fine. With continued monitoring and conservation efforts, these sharks will be around for a long time to come.

Spotted Wobbegong Shark

So, you think you know sharks, do you? They’re fast, agile, fish-eating, swimming machines, right? Think again. Let me introduce you to the spotted wobbegong shark (Orectolobus maculatus) and the rest of its wobbegong comrades. It’ll turn everything you thought you knew about sharks on its head.

What do wobbegong sharks look like?

The first thing you’ll notice about a wobbegong shark is that, well…it doesn’t really look like a typical shark. In fact, it looks more like a poofy, shaggy rug than a streamlined shark—hence the other common name of this group of predators, “carpet sharks.”

Wobbegongs lie still on the bottom of reefs and shallow waters, just like certain types of flat fish such as halibut and flounder. They have plenty of camouflage to help them out, too. They have a splotched, patterned back that blends in with the reef. They also have numerous shaggy, beard-like projections around their mouth, like the famous ghillie suits of military snipers. Finally, they have tiny vertical fins (dorsal and caudal fins) that help them keep a low profile.

The wobbegong also has a H-U-G-E head. It’s actually wider across than it is long! Remember this wide head; it’ll be an important factor later.

There are many species of wobbegong shark in addition to the spotted wobbegong. They generally look alike as well, and it can be difficult to tell them apart. In many cases, the location or the size of the shark is the determining factor in species identification.

This brings up an interesting question: if you have a small wobbegong, is it actually a smaller species, or just a juvenile version of a larger wobbegong? This question has baffled experts, but thanks to DNA sequencing and other new technologies, we now know that there are 11 other wobbegong species in addition to the spotted wobbegong:

Eucrossorhinus dasypogon – tasselled wobbegong
Orectolobus floridus – floral banded wobbegong
Orectolobus halei – gulf or banded wobbegong
Orectolobus hutchinsi – western wobbegong
Orectolobus japonicus – Japanese wobbegong
Orectolobus leptolineatus – Indonesian wobbegong
Orectolobus ornatus – ornate wobbegong
Orectolobus parvimaculatus – dwarf spotted wobbegong
Orectolobus reticulatus – network wobbegong
Orectolobus wardi – northern wobbegong
Sutorectus tentaculatus – cobbler wobbegong

Where do wobbegong sharks live?

While the name “wobbegong” might sound similar to Garrison Keillor’s fictional Minnesota town of Lake Wobegon, the two couldn’t be more different.

Wobbegongs (wah-buh-gongs) live in the Pacific and Indian oceans and have a very narrow range at that. The spotted wobbegong in particular is more common around Australian waters. Indonesian wobbegongs live in Indonesian waters, and Japanese wobbbegongs live in…you guessed it, Japanese waters.

Unlike a lot of other sharks that prefer cruising the open ocean, the wobbegong is more of a homebody. You might even call it a couch-potato shark. They usually pick a spot and plant themselves down, sometimes not moving for many hours at a time. In order to stay alive while stationary, they actually pump water over their gills with their cheek muscles to keep their blood oxygenated (since they aren’t moving around like most sharks do).

Wobbegongs also prefer shallow water, and they love reefs with all their nooks and crannies to hide in and hunt. Speaking of hunting…

What do wobbegong sharks eat?

Remember those big mouths that I told you to remember? Those come into key play here because a wobbegong will basically eat anything and everything moving that will fit into its mouth—and sometimes even things that don’t.

If they can’t fit something inside of their mouths, they’ll follow a trick similar to what wolves or bulldogs do. They’ll clamp down on the prey and simply hold it there until it does from exhaustion or suffocation (or drowning, in this case).

This behavior sometimes gets them into trouble with people. Wobbegongs won’t actively seek out people to hunt, but they’re sharks, and sometimes they make mistakes. Maybe a tasty-looking fish fin swimming past happens to be attached to a human leg: an unfortunate mistake for both the shark and the human.

It can be difficult to get wobbegong sharks off of you if they do clamp down, but it can be done. In fact, of 32 recorded wobbegong attacks, none were fatal.

Most of the time wobbegongs are content with simply sitting in place and letting prey come to them, although sometimes they will also actively hunt and move around. This is where some of the wobbegong’s special adaptations come into play. Their shaggy bearded projections will act like lures to draw in prey closer.

Once within reach, the wobbegongs suddenly take action. They’ll snap open their jaws, creating a huge suction draw that’ll suck in any nearby prey. It’s quite impressive to see!

Are wobbegong sharks in trouble?

Sometimes it seems like most stories of shark conservation are like witnessing the dying throes of a species. Luckily, the wobbegong’s story is a successful one that that we can learn from.

Wobbegongs have a good capacity to keep their population numbers up. They breed once every three years or so, and the viviparious (live-bearing) females can give birth to a staggering 21-37 pups per litter! (Just imagine if humans could do that…)

Wobbegongs don’t have a lot of commercial value. While you can find wobbegong on the menu in some local Australian fish n’ chip shops, they aren’t as widely eaten as some other sharks like porbeagles and mako sharks.

Wobbegongs used to be fished with very little regulation in Australia. However, after a 2007 report showed that the wobbegong population was decreasing, the government clamped down. They tightened up regulations for the commercial and recreational fishing industries in 2008. Since then it appears that the wobbegong population has been increasing. As long as we keep an eye on these shark populations and react if they appear to be going downhill, this is one shark story that will have a happy ending.

Shortfin mako shark

Imagine if you set out to create the leanest, meanest, fastest predatory shark the ocean ever saw. You might start out with a smooth, thin, torpedo-shaped body and add in some super-strong muscles attached to a powerful tail. To top it off, add a pointy snout that can cut through the water like glass.

Congratulations, my friend, you’ve just designed a mako shark. These crazy animals are the fastest known sharks in existence, clocking in at a record-shattering 60 miles per hour. That’s not the only cool thing about them, though—read on for more!

What is a mako shark?

Mako sharks are another nondescript gray shark. They don’t have any fancy skin patterns, but what they lack in decoration they make up for with a missile-shaped body, usually between 7-12 feet in length. They have large teeth—so big, in fact, that they still stick out when the shark closes its mouth!

Mako sharks come in two flavors: the shortfin mako (Isurus oxyrinchus) and the longfin mako (Isurus paucus). Shortfin makos are by far the most common species.

It’s unlikely you’ll run into the longfin mako, but if you do, consider yourself lucky. Scientists still don’t know a lot about this particular shark species yet. It’s thought that they live deep in the ocean, which might explain why shark scientists (with their boats on the surface) can’t get to them easily to study.

Mako shark biology turns it into a speed machine.

Mako sharks have a lot of biological features besides the shape of their body that make them shark speed champions. They possess two sets of muscles running down the sides of their body that act just like pistons in moving their tails back and forth. You can see how fast and agile they are in this video:

These powerful muscles also take advantage of countercurrent heat exchangers, a unique feature also found in species like salmon sharks and porbeagles. These are a unique way of lining up blood vessels going to and from the cold parts of the body (like fins) next to blood vessels coming from warm parts of the body (like the heart).

By lining up these two sets of blood vessels—cold with warm—the shark can retain heat from its own body so that its muscles get a warm boost. Warm muscles translate into more efficient muscles, so the shark can move even faster! In fact, the mako is one of the only shark species in the world that is warm-blooded, thanks to its countercurrent heat exchangers.

Where do mako sharks live?

Imagine a band centered around the world on the equator. That’s mako territory. They prefer living in the pelagic biome (i.e., the open ocean), so it’s not likely you’ll run into these guys unless you’re far away from shore.

Mako sharks like to move around—a lot. Some mako sharks have been recorded bouncing around the ocean more times than a pinball.

How are mako shark populations doing?

Both the shortfin mako and the longfin mako are classified as vulnerable according to the IUCN. That means that as a whole, mako sharks are just one step away from being endangered.

Just like with their porbeagle cousins, mako sharks are a popular fishing target. They have excellent meat, and those acrobatic maneuvers they can carry out underwater means they put up one heck of a fight.

Members of United Nations countries have agreed on certain regulations governing mako sharks under the 1995 Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks Agreement (UNFSA; say that ten times fast), however most countries aren’t abiding by these rules yet. Rather, mako shark conservation regulations are a bit piecemeal depending on what country you’re in (or near).

Because mako sharks tend to migrate so much, it’s hard to keep tabs on their population in any one area and apply a consistent set of rules. For example, what happens if a shark in Brazil decides to go on a sunset cruise to the United States, where a whole different set of regulations apply? Unfortunately, mako sharks don’t stay within the boundary waters of the countries they’re born in.

There are a lot of other compounding factors causing mako shark populations to be so low, and one of them is bad scientific data.

It’s important for scientists to know the age of sharks so they can put this information into models that generate sustainable harvest rates. Scientists used to think that mako sharks put down two growth rings per year in the vertebrae they use to age the sharks. However, they recently discovered that they actually put down one growth ring per year, just like normal sharks. This means that a shark with 30 growth rings is not 15 years old; it’s actually 30 years old. All the mako sharks scientists have aged are actually twice as old as we thought! This means the models were giving inaccurate data that’s potentially harmful to the population.

Luckily, mako sharks do have a pretty high ability to recover from low population sizes. Female mako sharks can give birth to anywhere from 10-18 pups every three years—that’s quite a lot of little sharks! Now we just need better, more consistent regulations across the different countries to allow the sharks to take advantage of this inherent capacity to grow fast, and then we won’t need to worry about having low mako shark populations anymore.

Burmese Python

The Burmese Python is one of the largest snakes in the world. It may not hold the record for the longest snake (given to the reticulated python) or the record for the heaviest (a green anaconda holds that), but it is very close in both aspects. Experts generally agree that the snake could approach 23′ long although snakes in the wild over 20′ are extremely rare.

Constricting power of the Burmese Python.

The Burmese python is basically a giant mass of muscle. It is a sit and wait predator that relies on it’s ability to subdue it’s prey via constriction. That means, that unlike vipers that rely on a relatively quick bit of toxic venom, these snakes must squeeze it’s prey to death. One too many owners of these snakes have found out just how deadly these coils can be. Every few years they tend to get out of their cages `

It doesn’t take a large Burmese python to kill a relatively large prey. People for instance, have died from 13′ pythons. They’ve also been both killed and consumed by 23′ pythons (a reticulated python).

What do Burmese Pythons Eat?

Burmese Pythons are opportunistic ambush predators that can consume prey from as little as about 5% of their body size to close to 50% of their body size. This means that the prey of a Burmese python will change throughout it’s life. Small individuals will feed on small mammals such as mice, rats and other similarly sized fur-bearing animals. They also feed on birds, both domestic and wild. As their size increases they may feed on larger prey, like pigs and goats. Burmese python that have invaded the everglades have been recorded preying on alligators and even adult deer.

In Florida, the invasive Burmese pythons have be shown to have the following species in their guts: Rabbit (Sylvilagus sp.) Hispid cotton rat (Sigmodon hispidus) Cotton mouse (Peromyscus gossypinus) Gray squirrel (Sciurus carolinensis) Fox squirrel (Sciurus niger) Domestic cat (Felis catus) Raccoon (Procyon lotor) Old world rats (Rattus sp.) Virginia opossum (Didelphis virginiana) Bobcat (Felis rufus) Round-tailed muskrat (Neofiber alleni) Rice rat (Oryzomys palustris) White-tailed deer (Odocoileus virginianus) Key Largo woodrat (Neotoma floridana smalli) Birds include the Pied-billed grebe (Podilymbus podiceps) Limpkin (Aramus guarauna) White ibis (Eudocimus albus) American coot (Fulica american) House wren (Troglodytes aedon) Reptiles American alligator (Alligator mississippiensis)

Python’s ability to digest large prey

Like deep sea fish whom consume extremely large prey relative to their body size, the Burmese python has an amazing ability to consume very large prey. It could easily digest something that was 50% the mass of the snake. To put that in relative terms, imagine a 200 pound human consuming a small 100 pound individual in one sitting. The thought is mind-blowing if you think about it. For these snakes though, it’s a common occurrence. To do this it must have a few special adaptations.

Python Jaws

First, it must physically get the prey into it’s mouth. This may be the biggest limiter. Often the shoulder blades on mammals are what limit the snake in it’s search for food. Unlike our jaws though, their mouth will open up to 150 degrees. The bottom jaw (lower mandibles) are also not connected in the front. Look at this photo of this python skull. Notice the separated lower jaws.

The size of the stomach

Oddly, these pythons do not need to get the entire prey item into their stomach to consume it. Instead, the stomach can start digesting part of the prey. Over time, the prey will move further into the stomach. The stomach may be as much as 1/4 the length of the python though. A 20′ snake for instance might be able to fit a 5′ prey item completely inside it.

Digestive Response of Burmese Pythons

The response of a Burmese python to a large prey is truly remarkable. In fact, it has become a model species for studying digestion. Leading the way is Dr. Steven Secor at the University of Alabama. He has been feeding Burmese pythons different types of prey and then trying to figure out what happens inside them. What he and his students have found is unlike anything we’re used to in humans.

Humans for instance, have fasting stomachs that are highly acidic. As food is consumed however, our stomachs are buffered and become less acidic. These snakes however, have a reduced acidity during fasting. As food is consumed, their stomachs change. The acidity and volume increase. Their intestines increase in size and the mass of the ventricle of the heart increases in size.

But how fast does a Burmese Python consume it’s prey you might ask? While this differs a bit in the size of their prey, the size of the snake, the type of prey, and the temperature of their surroundings, it is useful to look at the sequential slides of a Burmese python consuming an alligator.

What you’ll notice on day 1 is a fully intact skeleton of the alligator. All the major bones are present. By day 2, some bits of the jaw are starting to dissolve, but it’s still relatively intact. Day 3 and 4 show a great deal of dissolution. By day 5, there are only a few small bones left and by day 6, the alligator is completely consumed.

The only bits of most animals that are hard to digest by these pythons are those bits that contain keratin. Thus, finger nails, hair, claws and some antler-type material may come out in the feces. These serve as the only evidence of the prey item. This fact has made it next to impossible to find evidence of python attacks in the fossil record.

Where does the Burmese Python Live?

The Burmese python is native to south-east Asia from eastern India into Indonesia. It was previously listed as the same species as the Indian python (a very close relative). In many parts of their range they are threatened and fairly well. The Burmese python also lives outside of it’s range as an invasive species in south Florida, particularly in the everglades.

The Invasion in the Everglades

Ever since these snakes have been kept as pets, they have been released by their owners into the wild. A small burmese python will quickly outgrow a small cage and can often become a problem for the owners. Even though good homes could be found for these large individuals, people have a tendency to release some of them back into the wild (a practice that is both foolish and dangerous). However, this was likely not how the everglades got it’s problem burmese pythons.

In 1992, Hurricane Andrew devastated south Florida. The eye of the storm went right over Homestead, a small town just south of Miami. Here, a breeder’s facility was completely demolished and his snakes escaped into the wild. According to some estimates, it was just under 1000 individuals. This became ground zero for the invasion of the everglades.

This initial population didn’t seem to do anything though. It wasn’t until 2000 when the first problematic burmese pythons were discovered. The problem has grown. The government has taken different approaches to control the invasion. In some years they have had an open season on them – a collect as many as you can if you will. They’ve tried tracking males to breeding spots. They’ve tried tagging and baiting. Nothing seems to be a surefire way to get rid of them. They may be here to stay.

In 2017, the South Florida Water Management District decided they were going to have a bounty for these snakes. They hired 25 hunters at 8.25/hr to look for snakes. They were able to get an extra 25 dollars for every foot of the snake they brought in. These hunters however, are still not able to find too many. When we went out with them, they only had a couple of weeks left in the season and had only caught about 80 snakes.

What this means for south florida is unclear. We know that these are large apex predators, similar in the food pyramid to where the alligator stands. They likely will not replace the alligators, but merely become yet another predator in the system that organisms in the glades will have to deal with. Right now it seems that it is next to impossible to get them all out.