Port Jackson sharks share the same broad, flat nose as other bull sharks but what makes them unique is their harness-like bands that wrap around its body.  The largest of the bull sharks, the shark can grow up to 1.65m long, although the males are slightly smaller than the females.

They lay spiral-shaped eggs

There are a 3 main ways that sharks can produce offspring, including oviparity which means egg-laying, viviparity which means to give birth to live young and ovoviviparity which means to carry eggs that hatch inside the mother, before giving birth to the young.

Port Jackson sharks are oviparous, which means the females lay eggs. What’s most interesting about this however, is that the eggs are spiral-shaped. They are incredibly unique looking, and it’s common to find them washed up on beaches.

The mother will wedge the egg into rock crevices to allow it to harden, and the young will emerge within 10-12 months.

Port Jackson sharks are nocturnal

While we don’t know a lot about the way sharks sleep, we do know that some species are diurnal which means they are more active in the day like humans, while others are nocturnal and more active at night. Port Jackson sharks fall into the latter category.

You might be wondering why they choose to rest all day and then become active at night, and the answer is pretty simple: they hunt at night when their prey is most active. It would be pretty pointless for them to spend all day swimming around with nothing to eat!

During the day, they like to relax in caves as protection.

They have some unique markings

In the same way that humans can be identified by their unique fingerprints, scientists now believe that Port Jackson sharks can be identified using photo identification. This photo identification technology is also being used to identify other shark species, such as whale sharks who have each have unique patterns.

The banding around the top of the shark is absolutely unique to the individual shark. These harness-like markings typically cross the eyes, run along its back and cross the side of the body.

They are native to Australia

As the name would suggest, the Port Jackson shark can be found in the Port Jackson region of Sydney, Australia. However, they aren’t just found in that one area, as they have also been seen in the waters surrounding the whole of Australia, although they are most numerous along the South coast.

Port Jackson sharks typically live in rocky areas on or near the bottom of the sea.

Jaw-some teeth

When you think of shark teeth, you’d likely think of very sharp, pearly whites straight from the movies, but sharks can actually have a variety of teeth types and appearances.

Port Jackson Sharks have two primary sets of teeth. Their front teeth are sharp and pointy to grab and crush their prey, with the back sets being smooth and flat, making them ideal for grinding up the likes of crustaceans.

They can eat and breathe at the same time

Port Jackson sharks possess the unusual ability to be able to eat and breathe at the same time. You might be thinking “that doesn’t seem so unusual, I do that every day!”, but you’re not a shark.

Most sharks are unable to do this because they need to be swimming forward with their mouths open in order to water to pass over their gills, but this isn’t the case for Port Jackson sharks.

They achieve this via buccal ventilation which is the generation of an almost continuous water flow over the gills by compressing and decompressing their pharynx.

They can be called “oyster crushers”

Due to their diet, Port Jackson sharks are sometimes called oyster crushers as a nod to their feeding habits.

It’s not just oysters that must be aware of their fearsome gnashers, the sharks are also known for eating sea urchins, crustaceans, and other small fish.

We think that you’ll agree that Port Jackson sharks are not just your stereotypical apex predators. Instead, they offer a fascinating insight into how sharks have evolved differently over the course of millions of years to thrive in their specific environments.

You can visit the Port Jackson shark in our Coral Seas exhibit at Bristol Aquarium!

That’s right, as absurd as it may sound, not all fish are strong swimmers. In fact, some species can scarcely swim at all, and have instead evolved some pretty ingenious ways to stay afloat in our seas, oceans, rivers, and lakes.

So, of all the sub-par paddlers in the world’s waters, which stand out as the fish that flounder the most? Let’s take a look at some of the species that rank as the world’s worst swimmers, many of which are on display right here at Bristol Aquarium.

Seahorses

There are lots of attributes to seahorses (Hippocampus) that make them impressive and unique marine animals, but swimming isn’t one of them. Sure, they can propel themselves forward with their dorsal fins, but progress is slow and their body shape means they’re very unstable in the water.

Rather than relying on their abject swimming technique, then, seahorses use their powerful tails to anchor to nearby objects, including rocks, coral, and ship wrecks. This prevents them from being swept away in strong currents during feeding and breeding.

Clownfish

Marlin may have crossed the Pacific in search of Nemo, but did you know that the cute-as-a-button clownfish (Amphiprioninae) isn’t actually all that good at swimming?

It’s not that clownfish are unable to swim – they just choose not to. Once a clownfish has chosen an anemone in which to live, it will scarcely swim further than a few feet from its new home, meaning that the species hasn’t exactly evolved to have the strongest swimming technique of other tropical species out there.

Pufferfish

It’s safe to say that pufferfish (Tetraodontidae) aren’t the strongest swimmers in the big blue. Clumsy and ungainly in the water, these fish would stand little chance out-swimming predators. Lucky for them they have one of the most effective and ingenious defence mechanisms in the marine animal kingdom.

When threatened, pufferfish have evolved to literally “puff up”, tripling in size! So, what they lack in swim speed and agility, they make up for in sheer ferocity. Some pufferfish have sharp spines, like the Porcupine pufferfish, but they are only poisonous if eaten.

Batfish

Batfish aren’t winning any races against their fellow fish anytime soon. In fact, these unusual bottom-dwellers can barely swim at all.

Instead, they scamper across the seafloor on their pectoral, pelvic and anal fins, rather like a frog or crustacean. Lucky for them, they have no natural predators – good news when you move this slowly. They are, however, at risk from the effects of coral bleaching and habitat loss, like so many marine creatures.

Stonefish

Stonefish aren’t ones for swimming vast distances at high speeds in search of a meal. Indeed, it’s in their best interest to stay as still as possible and wait for prey to come to them.

Why? Not only are stonefish armed with some of the deadliest venom in the ocean, but they also rely on camouflage and cover to hunt their prey. That’s why these prehistoric-looking bottom-dwellers are most often found hunkered on the seafloor, with their unique, fossil-like appearance doing all the work while they wait for prey to take the bait.

So there you have it – five of the poorest and slowest swimmers in our oceans. There are plenty of other less-than-quick paddlers out there, so if you’d like to learn more, be sure to chat to one of our experienced aquarists during your visit to Bristol Aquarium.

How to swim better than a fish

Now that we’ve established that not all fish are strong swimmers, we thought it would be nice to offer a few tips and insights on how to improve your own swimming technique. After all, there’s nothing better than feeling confident in the water…

• Kick like you mean it: Most of a swimmer’s power comes from the legs, so building a solid swim kick will serve you well.

• Maintain a high elbow position: If you like to front crawl, be sure to maintain a high elbow position on your pull stroke. That way you’ll quickly gain momentum and cut through the water at a much snappier pace.

• Work on your breathing: If there’s one thing guaranteed to hold you back as a swimmer it’s breathing. Learning to breathe while swimming is one of the most difficult aspects of swim training, but is something you’ll need to master if you want to go from a good swimmer to a brilliant one.

Seahorses, pufferfish, and batfish may not be the most adept swimmers in the pond, but each has developed a unique way to cope with the demands of life beneath the ocean waves. If you’d like the opportunity to see some of the sea’s poorest paddlers in the flesh, book your tickets to Bristol Aquarium today.

Bristol Aquarium will be transforming into a port terminal this Summer Holidays to take its visitors on a voyage across the world’s oceans.

Visitors will pick up their tickets and passport at the check-in desk, take part in a postcard trail around the aquarium to fill in their passport and get involved in all of our scheduled activities.

Pack your bags and head to Bristol Aquarium this Summer to see our underwater animals up close!

Bristol Aquarium will be open from 10am until 6pm (last entry at 5pm) from Thursday 21st July 2022 to Sunday 4th September 2022.

The event is included in the usual admission price and tickets can be purchase online in advance or at the ticket desk. Bristol Aquarium does not operate on a ticket booking system so you do not need to choose a date for a visit, simply turn up on a date of your choosing. Tickets are valid for redemption for 6 months from the purchase date.