In this blog post, we will delve into the captivating world of electric eels, exploring their unique characteristics, behaviours, and the electrifying mechanism that sets them apart from other aquatic species.

What is an electric eel?

Electric eels, often referred to as such, are more closely related to catfish and carp than true eels. Their scientific classification is Gymnotidae. As fish, electric eels exhibit a distinctive social behaviour, forming groups known as swarms.

Electric eel vs true eel:

Contrary to their name, electric eels aren’t true eels. True eels belong to the order Anguilliformes, whereas electric eels belong to the order Gymnotiformes. The distinctions between these two types of aquatic creatures lie in their evolutionary history, morphology, and behaviour.

How do electric eels produce electricity?

Electric eels have a remarkable ability to generate electricity, a feature that sets them apart in the aquatic world. Each side of their body has around 70 columns. In turn, each column contains 5000–10 000 electrocytes. which act like tiny batteries. These cells discharge simultaneously when the eel feels threatened or is attacking prey, producing an electric shock of up to 860 volts. This defence mechanism is attributed to three organs: the main organ, Hunter’s organ, and Sach’s organ.

The purpose behind producing electricity is twofold: stunning prey and dissuading predators. The electric shock serves as an efficient means for the electric eel to navigate its surroundings, locate prey, and defend itself against potential threats.

What do electric eels look like?

Electric eels are often compared to true eels due to their long, slender bodies. They can grow up to 8 feet (2.5 metres) in length and have a snake-like appearance with a flattened head. Their thick, scaleless skin is usually dark grey to brown, while the underside is a yellow-orange colour. Interestingly, only 20% of their body length contains vital organs, with the remaining 80% dedicated to electric organs.

These creatures have poor eyesight but compensate by emitting a weak electric signal, functioning like radar to navigate, find mates, and locate prey. They lack pelvic fins and primarily extract oxygen from the water’s surface.

Habitat of an electric eel:

Electric eels inhabit murky pools and calm stretches in the middle and lower Amazon and Orinoco river basins. Unlike true eels, they exclusively reside in freshwater habitats. The distinct wet and dry seasons in their habitat bring about significant changes, influencing the availability of suitable environments for electric eels.

What do electric eels eat?

Adult electric eels are generalist carnivores, consuming fish, crustaceans, insects, and small vertebrates such as amphibians, reptiles, and mammals. Juveniles primarily feed on invertebrates, while newly hatched electric eels consume unhatched eggs. The electric eel’s electricity is a crucial tool for hunting, aiding in stunning and capturing prey.

Additional electric eel facts

1. Electric eels can leap out of the water to attack predators.
2. They lay eggs in nests made of saliva.
3. Electric eels can accidentally electrocute themselves and other eels.
4. With a shocking capability of up to 860 volts, they could power a 40-watt DC lightbulb.
5. Electric eels served as inspiration for the creation of the first batteries.

Electric eels, with their electrifying abilities and unique characteristics, continue to captivate scientists and enthusiasts alike. Beyond their captivating features, these creatures play a vital role in maintaining the balance of their freshwater ecosystems.

Here at Bristol Aquarium, we are home to honeycomb moray eels and garden eels. In particular, honeycomb moray eels are fascinating creatures with two sets of jaws, making them incredible predators. You can find them in our Coral Seas exhibit!

For a chance to see our eels up close and personal, book your visit to Bristol Aquarium today!

In this blog post, we embark on an exploration of this fascinating invertebrate, delving into its discovery, characteristics, and the secrets behind its seemingly eternal life.

What is an immortal jellyfish?

The immortal jellyfish (Turritopsis dohrnii) earns its mesmerising nickname due to its remarkable ability to reverse its ageing process and revert to its juvenile form.

This unique creature belongs to the phylum Cnidaria, which includes a group of small, predatory animals including jellyfish, corals and sea anemone. While it may share similarities with other jellyfish, the immortal jellyfish has distinct capabilities which set it apart as one of the most curious organisms in the ocean.

When was the immortal jellyfish discovered?

First described by scientists in the 1880s, the immortal jellyfish’s extraordinary capabilities were only fully understood in more recent years – in the 1980s to be precise. Student scientists Christian Sommer and Giorgio Bavestrello collected the jellyfish and through experiments, they discovered the immortality of the species, which garnered lots of attention.

Its peculiar ability to revert its lifecycle to its juvenile stage, essentially escaping death, has made it the focus of extensive scientific research. The revelation of its biological immortality has sparked interest not only in the scientific community but also among the broader public intrigued by the mysteries of the natural world.

What do immortal jellyfish look like?

The immortal jellyfish is a delicate and almost transparent creature, making it nearly invisible as it drifts through the ocean currents. It is only around 4.5mm wide and tall, and is likely smaller than your little fingernail! Its body is bell-shaped, and can have anywhere from 8 to 80 white tentacles depending on its age.

Similar to other jellyfish, this species has no central nervous system or brain, as well as no other organs like a heart. This is why jellyfish are usually referred to as simple bodied invertebrates.

How does the immortal jellyfish reverse its lifecycle?

The key to the immortal jellyfish’s unique ability lies in its capacity to undergo a process called transdifferentiation. When faced with unfavourable environmental conditions, stress, or reaching the end of its natural lifecycle, the jellyfish can transform its adult cells into specialised cells, effectively regenerating itself back to its juvenile polyp stage.

This remarkable feat allows the immortal jellyfish to escape death and start its life cycle all over again. What’s more, this process can be repeated over and over again. This is an incredibly rare ability!

Immortal jellyfish habitat

These incredible creatures are thought to have originated in the Mediterranean Sea, but they can be found all around the world, preferring tropical and temperate waters. They often inhabit coastal areas, where conditions are preferable for their survival.

Immortal jellyfish diet

Immortal jellyfish are carnivores, primarily preying on plankton, larvae, fish eggs and other microscopic organisms. Their diet reflects their role in the marine ecosystem, playing a part in the delicate balance of ocean life. However, while they may be able to achieve some form of immortality, they are not protected from the threat of predators! Animals that prey on the immortal jellyfish include turtles, penguins, larger fish, and even larger jellyfish.

Immortal jellyfish vs common jellyfish

While the immortal jellyfish shares similarities with its jellyfish counterparts, several key differences set it apart. One of the most obvious distinctions is its ability to reverse its lifecycle, a feature absent in common jellyfish. Additionally, the immortal jellyfish tends to have a longer lifespan even without regenerating.

Comparing their habitats, common jellyfish can adapt to a broader range of environmental conditions, whereas the immortal jellyfish prefers specific climates, usually warmer coastal waters. These differences highlight the unique variations that occur between species of the same family.

In terms of diet, both the immortal jellyfish and common jellyfish are carnivorous, preying on small marine organisms. However, the immortal jellyfish’s regenerative abilities provide it with a potential advantage in times of scarcity, allowing it to survive conditions that might be fatal for other jellyfish.

For more amazing jellyfish facts, check out our list!

The immortal jellyfish, with its captivating abilities and ethereal presence, stands as a testament to the wonders of the natural world. Its discovery has opened new avenues of research and deepened our understanding of life in the ocean. Don’t forget to book your tickets today to come and see all of our incredible sea creatures for yourself!

Skinny, long, and live in water are all phrases that can be used to describe both eels and sea snakes, but one’s a reptile and one’s a fish, so what is the difference?

What is a sea snake?

A sea snake, as the name would suggest is the name for a plethora of snakes, that spend significant time in the water, usually to hunt for food. Sea snakes, despite spending a lot of time in water, are still reptiles.

Their bodies are specifically adapted to make them excellent swimmers compared to their solely land-dwelling cousins. An example of such an adaptation is their paddle-like tails that allow them to propel themselves through the water.

Sea snakes do not have gills so they cannot breathe underwater, but they are able to hold their breath for extended periods of time and are also able to absorb oxygen into their blood through their skin.

What is an eel?

Eels, on the other hand, are a type of slender fish that is visually similar to a snake. Unlike most other fish, eels lack pelvic fins and only have very small pectoral fins.

Much like sea snakes, an eel’s body is slender and adapted to glide through the water by generating waves up their body. Eels can also swim backwards by reversing the waves’ directions.

Key differences in appearance

Sea snakes and eels are both very similar-looking animals, but you’ll be interested to know that there are some key differences to set them apart.

The main difference in how an eel and a sea snake look is that a sea snake doesn’t have any fins or gills.

As well as this, when in water, eels are said to resemble a ribbon gliding through the water, whereas sea snakes resemble a thin piece of rope.

Habitat differences

Eels can be found in both seawater and freshwater, with most living in the sea. They may live in the shallower waters and burrow in the sand and mud, while other species live much deeper. On the other hand, sea snakes are mostly found in the tropical waters of the Indian Ocean and western Pacific Ocean.

Sea snake vs eel diet

Due to their widely differing habitats, it is unsurprising that even though they look similar, sea snakes and eels have vastly different diets.

Sea snakes rely primarily on small fish and fish eggs for sustenance which are found in abundance in the oceans that they inhabit.

Eels on the other hand, must broaden their horizons, feeding on not only small fish but also invertebrates, crustaceans, shrimp, crabs and sea urchins. Some species of eel are even cannibalistic, meaning they eat other eels!

How long do sea snakes and eels typically live for?

As with most animals, the lifespan can vary wildly depending on what species it belongs to.

For example, the honeycomb moral eel (Gymnothorax favagineus) is known to live to approximately 30 years, with its European cousin (Aguilla anguilla) being known to live up to around 50 years, although an average lifespan of 20 years is much more common. While we know very little about the lifespan of a sea snake currently, scientists agree that most species live up to around 5-10 years on average.

Defence mechanisms

Despite their relatively small stature, eels and sea snakes are both formidable opponents that you wouldn’t want to swim into in a hurry! Let’s look at how these incredible animals defend themselves from predators.

Electric eels are known for their ability to produce electricity to shock any predators that get too close – however, they aren’t an eel at all! Electric eels are actually a group of knifefish, that are closer in relation to catfish than true eels.

Other eels defend themselves using incredibly strong jaws and sharp teeth that produce a seriously nasty bite if threatened or disturbed. Some species of eel are also nocturnal meaning that they are less likely to encounter fish that mean to cause them harm.

Like many species of terrestrial snake, most sea snakes have a venomous bite. They use this to capture their fast moving prey. The venom from certain species of sea snake can be potent but luckily sea snakes are generally very reluctant to bite humans unless handled without care.

There you have it! Despite their many similarities, there is an awful lot that separates eels and sea snakes, whether it be the small differences in their appearance, their diet or location. Come and see our eels for yourself at our Coral Seas exhibit!

Sharks are no different in this regard, but which senses do they rely on the most? In this blog, we’ll explore the senses that sharks use to catch their prey, what makes them unique and what similarities they share with other fish.

How far can sharks smell? 

Sharks have an incredible sense of smell, among the best in the animal kingdom. They use their sense of smell as their primary weapon to track and catch their prey. Sharks can detect smells at between one part per 25 million and one part per 10 billion, depending on the chemical, and the species of shark. This means some species such as Great white sharks can smell about one drop of blood in a small swimming pool.

Sharks use an organ called the olfactory bulb that is located in their noses to detect blood in the ocean.

Do sharks have good eyesight?

Because of their incredible sense of smell, people often assume that sharks have poor eyesight, but this is false.

Most sharks have sight that becomes more acute when 15 meters or closer to an object, this is when the sense of sight is their dominant sense. Some species of deep-water sharks even have larger eyes that detect very faint glimmers of light.

The reason that a shark’s eyesight isn’t better, is simply that they don’t need it to be any better! They’ve survived for at least 450 million years by relying primarily on their sense of smell.

How well can sharks hear?

Sharks have a very fine-tuned sense of hearing which is more sensitive to low frequencies (10-800Hz). This is because injured or dying fish let out sounds at this frequency, meaning that sharks can determine where an easy meal might be.

They can hear sounds from a fair distance away too, despite only being a tiny opening in their head. According to University College London, sharks can hear sounds from up to 800 feet away.

How sharks use their sense of touch

Much like humans, sharks have touch receptors all over their bodies that can detect whenever something is close enough to be touching them. For smaller sharks, such as the Port Jackson shark, this could be predators or prey, so potentially the difference between life or death.

What do sharks taste?

You might think that because a shark is having to work hard for every meal, they can’t afford to be picky but you couldn’t be further from the truth.

Sharks have taste receptors in their mouths that detect taste and are known to reject meals that are distasteful. Some scientists suspect this is why shark attacks on humans are incredibly rare.

Electro-sensory system & lateral line

Sharks possess a remarkable electro-sensory system, relying on specialised cells called electroreceptors concentrated in the ampullae of Lorenzini around their head. These receptors detect electric fields generated by living organisms, aiding sharks in hunting by sensing the bioelectric fields of potential prey, even in darkness.

Additionally, sharks use a lateral line, a network of sensory cells along their body, to detect water movements, pressure changes, and vibrations from nearby objects – this is how the Blind Cave Fish sees.

This dual sensory adaptation enhances sharks’ awareness, facilitating efficient navigation and contributing to their success as predators in diverse underwater ecosystems. The electro-sensory system and lateral line showcase the extraordinary capabilities that make sharks highly adapted to their aquatic environments.

It is clear to see that sharks, as apex predators, rely on a combination of finely tuned senses to navigate and hunt in their diverse underwater habitats.

While their incredible sense of smell serves as a primary tool for tracking prey, their eyesight is not to be underestimated, allowing them to see between 10 and 15 meters even in murky waters.

During your next visit to Bristol Aquarium, you can not only appreciate the beauty and danger of sharks but also their incredible adaptations that have allowed them to stay at the top of the food chain for almost half a billion years!

So, if you’re hoping to learn a little more about these fascinating, spiny creatures, let’s dive straight in and understand just what is a sea urchin.

What is a sea urchin?

Sea urchins belong to a family called Echinodermata; a term that means spiny-skinned. This Phylum is also home to the likes of starfish, brittle stars and sea cucumbers. As a group, these animals are all known as echinoderms.

As they are spherical in shape and often live on the ocean floor, it’s easy to see why they might be seen as a plant, but they are in fact invertebrates. Sea urchins have been around for 450 million years, making them older than dinosaurs!

Types of sea urchins

There are just under 1,000 different species of sea urchins, each with their own individual characteristics and behaviours. For example, the Diadema sea urchin is one of the most ecologically important species as it helps to keep Caribbean coral reefs healthy.

Here at Bristol Aquarium we have our very own Diadema setosum sea urchin, also known as the long-spine sea urchin. It gets its name from its extremely long, hollow spines that can grow up to 30-40cm. Typically found in the Indo-Pacific region, its spines are mildly venomous but not fatal to humans. Interestingly, this particular species has been observed to have some of the best vision amongst sea urchins and can also rapidly invert its body and “run” on the tips of its longest spines! You can come and see this fascinating species in our Learning Lab.

The red sea urchin (Mesocentrotus franciscanus) is the largest species, which has a skeleton of around 18cm in diameter with spine lengths up to 8cm.

There are also a number of edible species of sea urchins. They are primarily used in Japanese uni sushi.

How to identify a sea urchin

Sea urchins are typically very bright in colour and are completely covered in sharp-looking spines. Fun fact: the word ‘urchin’ comes from an old word for hedgehog!

Older species have shorter, stubby spines while newer species have much spikier spines and are typically recognised as modern sea urchins.

Like other echinoderms, sea urchins have an internal skeleton that’s known as a test, which is usually a sphere shape. This is made from a type of calcium carbonate that holds the sea urchin together. These tests have five symmetrical parts around a central point, known as radial symmetry. This is also very similar to starfish.

Sea urchins can’t swim unlike other sea creatures amongst them. Instead, they have tube feet to move along the sea floor.

Habitat of a sea urchin

As they can’t swim, you’ll find sea urchins along the seabed where they typically favour corals and rocks to help them move around. They live in every ocean around the world, with some living in shallower or deeper waters depending on their species. The deepest a sea urchin has been found is 7,340 metres.

This means sea urchins live off the coast of the UK too, such as the green sea urchin (Psammechinus miliaris), which is primarily green with purple tips. The common sea urchin, which is usually pink in colour, can also be found off most coasts on the UK. If you’re lucky, you might catch a glimpse of one in a rockpool.

What do sea urchins eat?

While the main diet of a sea urchin consists of algae, they are actually omnivores. They will eat the likes of sea cucumbers, mussels and sea sponges. As sea urchins aren’t particularly agile, they have developed a method of eating that includes scraping algae into their mouth – which is on their underside.

Sea urchins have a unique chewing organ called the Aristotle’s lantern, which is made up of complex jaws and just 5 teeth that are able to sharpen themselves.

Lifespan of a sea urchin

The lifespan of a sea urchin can depend on its species, but they have been known to live anywhere between 20-200 years. For example, it used to be believed that red sea urchins lived only 7-10 years, but more recent findings show that they can actually live up to 100 years.

However, sea urchins can be very sensitive to any changes in their environment, such a change in the water’s pH and rising temperatures. In this sense, sea urchins can act as an early warning for problems in the wider ecosystem. Some species of sea urchins are considered to be in severe decline.

Are sea urchins dangerous?

Sea urchins may look a little bit scary with their spines, and it’s probably best that you steer clear of touching them! Some species have venom in their spines or in their pedicellariae, which is a defensive pincer. The flower sea urchin (Toxopneustes pileolus) is the most toxic. You’ll find this species across the Indo-West Pacific, from Okinawa in Japan to Tasmania in Australia, as well as the East African coast.

However, sea urchins are very passive and injuries usually only occur when a swimmer brushes against the spines or steps on one by accident.

So, if you’re hoping to come and catch a glimpse of some echinoderms at Bristol Aquarium, come on down to the learning lab to see our long-spined sea urchins and our Ocean Floor exhibit where you can see the common starfish! Don’t forget to book your tickets today. 

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.

There are more than 500 species of shark that can be found in today’s oceans. These range from tiny Dwarf Lantern Sharks to huge Whale Sharks, each with their own set of unique characteristics. In this blog, we’ll tell you all about the Japanese Banded Houndshark (Triakis scyllium): where you can find them, how you can spot them and what makes them one of our favourite dorsal-finned friends.

They can grow up to 1.5 metres long

Although they’re not the biggest sharks in the world, an accolade that sits firmly with the massive whale shark, these awesome fish can grow up to 150cm, so still pretty big. The female Japanese Banded Houndsharks are slightly bigger than their male counterparts, reaching their full size between 106cm-117cm after 6-7 years, compared to the males who grow up to 93-103cm. Some individuals have been known to grow up to 150cm.

Japanese Banded Houndsharks have distinctive black rings around their bodies

Banded Houndsharks are known for their distinctive black rings that circle around their slender bodies, which gives them their name. It’s worth nothing that these markings do fade with age. Houndsharks more generally are known for their oval-shaped eyes, two large, spineless dorsal fins, and a single anal fin.

Like most sharks, the Japanese Banded Houndshark has five gill slits on either side of its body.

Be sure to be on the lookout for this beautiful creature when you visit Coral Seas at Bristol Aquarium.

They are typically bottom dwellers

Similar to a typical moody teenager, Banded Houndsharks are solitary and largely nocturnal, meaning they sleep through the day and are active at night. During the night, they tend to stick near structures and the ocean floor, at depths of about 150m, to avoid larger fish that might target them as prey. This means they are known as bottom dwellers.

They are primarily solitary animals, although they have been known to come together with there is an abundance of food. They also have a funny habit of piling on top of each other on the sea floor, particularly when they are resting.

Banded Houndsharks are ovoviviparous

Most species of shark give birth to live young, but the Houndsharks give birth through the process of ovoviviparity. This means their young are formed from eggs, which are carried inside the mother to provide extra safety from potential predators. The egg will hatch inside the mother who can then give birth to the live young.

In one litter, Houndsharks can lay up to 42 pups! Houndshark pups take between 9 and 12 months to fully grow inside their mother. If you think 42 sounds like a lot of babies, some other species of shark like blue sharks can give birth to more than a hundred at once!

You’ll find Banded Houndsharks off the coast of Japan

The clue really is in the name as to where you’ll find the Japanese Banded Houndshark! They live in the North-Western section of the Pacific Ocean close to places like Japan, China, Korea and even Southern Russia.

Sharks can be found throughout the whole world in saltwater (oceans and seas), although some species call rivers and lakes their home such as bull sharks and, funnily enough, river sharks.

In the UK, you’re unlikely to see a houndshark, but you will see smooth-hound sharks which are in the same family! This species is often found off the coast of the UK. There are over 20 shark species that call the UK their home including the Lesser Spotted Catshark – which you can also see here at Bristol Aquarium!

Banded Houndsharks are considered endangered

According to the IUCN Red List, Banded Houndsharks are considered endangered. Their numbers in the wild are decreasing mainly due to bycatching – accidental catching of fish. However, there is a growing market for shark fins for dishes such as shark fin soup, which is popular in Chinese cuisine.

Because sharks are apex predators, their population decreasing can have a drastic impact on the wider health of the marine ecosystem because other populations are not kept in check.

Those were just some of the incredible facts about Banded Hound Sharks. We hope we’ve helped to reveal a little bit more about these incredible sharks and to know that there is more to them than just what you see in the movies. If you’d like to learn more about these animals, you can book your tickets and ask one of our trainers down at Bristol Aquarium.

The Blind Cave fish, also known as the Mexican tetra (Astyanax mexicanus) is a strange looking species, no less because of their complete lack of eyes and translucent pink skin, however, they are a fascinating example of how the environment can directly impact how an animal looks, feeds, and behaves.

Why is this species of fish blind?

While a blind fish might seem completely counterproductive, it’s actually very clever. Blind Cave fish are blind on purpose, because they have evolved to survive without the use of their eyes.

The eyes and parts of the brain that process visual information use a lot of energy to operate, which means that when living in environments where food is scarce, nature will often take its course to ensure that the animal is able to conserve its energy for the absolute necessities, such as keeping their vital organs working.

The Blind Cave fish evolved to eventually have no eyes, and have survived long enough to pass this characteristic onto its offspring. The species is able to conserve its energy from not having to try and see in the murky depths, and instead using that energy to hunt for food and mate. This is known as a process called pleiotropy, in which the genes usually needed for eye development are reassigned to other areas, like increasing the number of taste cells for finding food.

The complete lack of sunlight is also the reason behind their almost see-through skin which lacks a lot of pigmentation, with only a slight pink hue that can be compared to albinism.

Where do Blind Cave fish come from?

Blind Cave Fish originate in Mexico, the United States and Guatemala, which is why they’re also known the Mexican tetra.

There are actually two types of this species – one with eyes and one without. While one has evolved to have no eyes because of the depths it lives at, the other type lives in fast-moving rivers and still relies on its eyesight to navigate its environment and find food.

Mexican tetras are freshwater fish who like to live in tropical waters of about 20-25°c. They are quite hardy fish meaning they can survive within quite broad parameters, but are still sensitive to big changes in the environment such as large spikes in ammonia from decaying matter.

What do Blind Cave fish eat?

Because these Cave fish live so far down in pretty inhospitable conditions, food can be scarce, meaning their options are limited.

Despite this, Blind Cave fish survive on worms, snails, other small fish, and insects. They are also considered omnivorous because they can eat algae and other plant matter when other animals aren’t available to eat.

If you’re wondering how they find their food, then wonder no more. All fish have organs called lateral line organs which help detect water displacement. Over time, Blind Cave fish have evolved very sensitive lateral line organs which means they can find their way around without the need for sight.

They can also remember where objects are to stop themselves from constantly bumping into things, despite the common myth that fish have bad memories. This can, however, take time when first introduced to a new environment.

What are Blind Cave fish like?

As with most fish in the Tetra family, the Mexican tetra is a naturally schooling fish which means that they like to swim around in groups of at least 6. The blind variation of the fish doesn’t seem to be a schooling fish as such, but they do tend to congregate in groups when in the wild.

They are known to be quite peaceful fish although they can become more aggressive as they age and can sometimes nip tankmates if they mistake them for food. In the wild, and in aquariums, they live quite happily with other fish species.

Are there other blind fish species?

There are a whole host of cave fish species, some of which are also blind. This includes the southern cavefish (Typhlichthys subterraneus) found in eastern US, and the Ozark cavefish (Amblyopsis rosae). There are also a number of cave shrimp that are blind, including the British cave shrimp (Niphargus glenniei) and the Kentucky cave shrimp (Palaemonias ganteri). Most blind fish live in caves or other dark dwellings, and have no use for good vision.

That’s all you need to know about the Blind Cave Fish. They truly are fascinating fish, with more to them than meets the eye. You will be able to see these fish, even if they can’t see you, at our Edge of the Rainforest exhibit.

Learning More about The Octopus

Octopuses, the mesmerizing cephalopods, are a testament to the marvels of evolution. Each species boasts distinct features and behaviors, but all share common traits that make them stand out in the aquatic world.

Here at Bristol Aquarium, we have Octavia! Octavia is a Common Octopus who is a cheeky character! She likes to play tug of war, and she often wins!

Here are some other facts you can sink your teeth into…

1. Shape-Shifting Chameleons: Octopuses are known for their shape-shifting abilities. Their skin can change color and texture almost instantly, enabling them to blend seamlessly with their surroundings. This remarkable camouflage skill is a sight to behold.
2. Problem-Solving Prowess: These intelligent creatures are avid problem solvers. Researchers have observed octopuses navigating mazes, using tools, and even exhibiting playful behavior. Their cognitive abilities continue to astound scientists. Take a look at this video to learn more!
3. Remarkable Dexterity: With eight incredibly flexible arms lined with hundreds of sensitive suckers, octopuses display remarkable dexterity. They can manipulate objects and capture prey with astonishing precision.
4. Masters of Adaptation: Octopuses are highly adaptable, inhabiting a variety of marine environments. Some dwell in the depths of the ocean, while others thrive in shallow coastal waters. Their versatility is a testament to their evolutionary success.
5. Short But Spectacular Lives: Despite their impressive abilities, octopuses have relatively short lifespans, typically ranging from one to five years, depending on the species. After reproducing, most octopuses die, leaving behind a legacy of new generations.

If you’re interested in the Biology of the Octopus, this is an interesting video to watch too!

Conservation Efforts

While octopuses are not currently listed as endangered, they face threats from human activities, including overfishing and habitat degradation. At Bristol Aquarium, we are committed to raising awareness about the importance of marine conservation. Our efforts include promoting sustainable fishing practices, advocating for the protection of marine ecosystems, and supporting research to better understand and protect octopuses and their habitats.

As we celebrate World Octopus Day at Bristol Aquarium, we invite you to join us in exploring the captivating world of octopuses. These intelligent, adaptable, and masterful creatures are a testament to the wonders of our oceans. Through our special exhibits and dedication to marine conservation, we hope to inspire a deeper appreciation for octopuses and the fragile ecosystems they inhabit. Come dive into the depths with us and witness the magic of octopuses like never before.