Oct 21
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Endangered Species of the Week: European eel

European eel (Anguilla anguilla) photo

European eel (Anguilla anguilla)

Species: European eel (Anguilla anguilla)

Status: Critically Endangered (CR)

Interesting Fact: It is thought that all European eels spawn in the Sargasso Sea after a migration of around 5000 km from European rivers.

European eels are catadromous fish, meaning they spend much of their lives in freshwater but migrate to the sea to breed. Transparent eggs hatch into larvae known as leptocephalli, which drift in the sea for up to three years. Pushed towards the European coast by ocean currents, they then undergo metamorphosis into young, transparent eels known as glass eels. Becoming darker, the young eels, now known as elvers, start to migrate up freshwater streams in large numbers. These eels remain in freshwater for up to 20 years, growing up to 1 metre long. Once sexually mature, the eels migrate back to the Sargasso Sea to spawn. Relatively little is known about the life history and migration routes of the European eels once at sea.

Eel populations have declined in recent years. The threats facing the species are not clear but it is thought that pollution, overfishing, habitat degradation, parasite infection and climate changes are all potential causes of the decline. Regulations are in place to protect these rare eels, including reducing fisheries, restocking, improving habitats and making rivers passable.

Find out more about European eels and their conservation on the eeliad project website.

See videos and images of the European eel on ARKive.

Lauren Pascoe, ARKive Researcher

Aug 26
Share 'Endangered Species of the Week: Atlantic halibut' on Delicious Share 'Endangered Species of the Week: Atlantic halibut' on Digg Share 'Endangered Species of the Week: Atlantic halibut' on Facebook Share 'Endangered Species of the Week: Atlantic halibut' on reddit Share 'Endangered Species of the Week: Atlantic halibut' on StumbleUpon Share 'Endangered Species of the Week: Atlantic halibut' on Email Share 'Endangered Species of the Week: Atlantic halibut' on Print Friendly

Endangered Species of the Week: Atlantic halibut

Atlantic halibut (Hippoglossus hippoglossus) photo

Atlantic halibut (Hippoglossus hippoglossus)

Species: Atlantic halibut (Hippoglossus hippoglossus)

Status: Endangered (EN)

Interesting fact: The Atlantic halibut is the largest flatfish in the world.

Like other species of flatfish, the Atlantic halibut is curiously adapted to life on the ocean floor. They have evolved to lie on one side of their body, flattened sideways. The Atlantic halibut lies on its left side and both eyes tend to migrate the right side of the head during development.

The Atlantic halibut is found in the cold waters of North Atlantic coasts. Larvae can be found drifting within the water column, and will migrate to the ocean floor when they reach about 4 centimetres. The Atlantic halibut has a relatively slow growth rate and can live up to 50 years. Young Atlantic halibuts feed on crustaceans, while older fish tend to hunt other fish, such as cod, haddock, herring and skate.

The slow growth rate and late onset of sexual maturity makes the Atlantic halibut extremely vulnerable to the effects of overfishing. Over the last two centuries the Atlantic halibut has suffered massive declines throughout its range due to overfishing. Today, population levels are still in decline. They are now too low to sustain target fisheries, but the Atlantic halibut is still caught as bycatch by bottom trawlers and longliners.

There is currently no management plan in place for this fish and it is thought that numbers of Atlantic halibut will continue to decline. The recovery and survival of this Endangered flatfish species depends on reducing bycatch in other highly exploited fisheries.

Find out more about this endangered flatfish on the Fisheries and Oceans Canada website.

See images and videos of the Atlantic halibut on ARKive.

Lauren Pascoe, ARKive Researcher

Aug 9
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ARKive’s Top Ten Shark Videos

As most of people don’t have enough spare time to watch the 8,522 videos currently on ARKive (although you may wish you did), we thought we’d give you a helping hand by choosing what we considered to be the top ten videos of one of the world’s most endearing animals: the shark. After perusing all of the magnificent shark footage on ARKive we managed to whittle them down to just ten terrifying, awe-inspiring and bizarre videos.

Gentle giants

The whale shark is the biggest fish in the world, measuring as much as twelve metres and weighing up to 12,500 kilograms. It is a fairly docile species and feeds mostly on plankton and small fish, actively sucking in prey through its large mouth. Its sheer size can be acknowledged when compared with the diver in this video:

Whale shark with snorkeler

It’s fin may cut the surface of the water in a way which could instil fear into the most courageous humans, but the basking shark is more interested in devouring microscopic prey. The basking shark is the second largest fish in the world and has a mouth that can measure up to a metre across when fully open. See it feeding in this fascinating footage:

Basking shark feeding

Out of the ordinary

The mysterious megamouth shark was only described as recently as 1976 and is so genetically different from other sharks that it was placed in its own family. It can reach over five metres in length and its oversized mouth has over 50 rows of tiny, hooked teeth. See this strange species in action in this video:

Megamouth shark

Friends with benefits

The Greenland shark is one of the largest sharks in the world, measuring up to seven metres. Almost all Greenland sharks are parasitized by a minute crustacean which attaches itself to the shark’s cornea and gradually destroys the host’s eyesight. It is thought to be a mutually beneficial relationship as the crustacean may act as a lure for fish, although this is unconfirmed. See it in action here:

Greenland shark with parasitic copepod

The strange-looking scalloped hammerhead has a mutually beneficial relationship with cleaner wrasse. This helpful fish eats parasites from the skin and mouth of the scalloped hammerhead shark, as well as cleaning any wounds, as shown in this video:

Barber fish cleaning scalloped hammerhead

Remarkable reproduction

Most sharks are ovoviviparous, with the young developing within eggs in the body of the female. The eggs then hatch inside the female, who then gives birth to the well-developed young. However, the lemon shark, similarly to humans, is viviparous and the young develop inside the female, while receiving nutrients from an internal placenta and the female then gives birth to live young. See this extraordinary event unfold here:

Newborn lemon shark pup

Expensive taste

The salmon shark, as its name suggests is thought to be one of the main predators of Pacific salmon. It is similar in appearance to the great white shark and shares its excellent predatory skills. The salmon shark may have the highest body temperature of any shark, which allows them to maintain warm muscles and organs, so they are still able to hunt in the ice cold waters of the North Pacific Ocean. See this giant in its habitat here:

Salmon shark

Quick off the mark

The shortfin mako is thought to be the fastest shark species and is capable of reaching speeds of up to 35 kilometres per hour. Its high tail and efficient heat exchange system enable it to quickly pursue its prey, as shown in this video:

Shortfin mako

Fearsome fish

No list about sharks would be complete without mentioning the formidable great white shark. A tremendously skilled predator, it is at the top of the marine food chain and is known to hunt fish, turtles, molluscs, dolphins, porpoises and seals. Their powerful bodies enable them to leap from the water in pursuit of prey, as shown in this video:

Great white shark breaching

Fighting back

The tiger shark is one of the largest shark species and is known for its voracious appetite, eating anything from fish to car license plates. Although the inanimate objects it predates on are unlikely to fight back, its more alive prey may create more problems, much like the loggerhead turtle in this video:

Tiger shark feeding on fish carcass

Hannah Mulvany, ARKive Species Text Author Intern

Jul 28
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National Marine Week

This week marks National Marine Week here in the UK where Wildlife Trusts up and down the country are putting on a whole host of marine related events to encourage people to get out and about and explore our stunning coasts. From rock pool exploration to searching the sands, get in touch with your local Wildlife trust to find out more about what’s going on and how you can get involved.

Why not start your marine adventures by dipping your toe into ARKive and exploring our many thousands of fascinating sea animals and plants.

On the sand

A sandy beach can often resemble a desert but if you look carefully, you can often find the sand packed with lugworms. These worms can grow up to an impressive 20 centimetres long and can be located by looking for casts of defecated sand material above their burrows. Lugworms also provide an important food source for many different species of seabirds.

Lugworm casts

Casts of deposited sand material are a sure indicator for the presence of lugworms

 

Lugworm photo

A lugworm outside its sandy burrow

Into the sea

Though we may complain that the sea is usually to cold to swim in, Britain’s temperate waters are frequented by over 23 different species of dolphins and whales including the bottlenose dolphins.  If you are going anywhere by boat this summer you may well see theses energetic dolphins jumping out of the sea and even riding the swell at the front of the boat.

Bottlenose dolphin pod

Pods of bottlenose dolphins are often not at all shy of boats

Britain’s cooler waters are also visited by fascinating species of fish such as basking sharks, theses humongous fish can reach weight of over 3 tonnes, all on a diet of plankton!

Basking shark photo
The basking shark requires its large mouth to passively feed on plankton

On the cliffs

A vast amount of the British coastline is cliff , which provides vital nesting sites for a huge variety of sea birds. The most distinct and recognisable of all of these is probably the puffin.  Breeding colonies are located around the UK and the birds are present from April to mid August. Visitors to these locations are usually well rewarded with sights of puffins returning to their cliff top nest burrows with beaks stuffed full of sand eels.

Puffins

Puffins perched on the cliff edge

 

Photo of a puffin with sand eels in beak

A puffin with a successful catch of sand eels

Exploring the rock pools

Britain’s rocky shores are loaded with rock pools just waiting to be discovered. Though they may look like mini underwater paradises, rock pools are often harsh environments and are prone to high temperatures and variation in salinity. Some of the animals you can hope to see in rock pools around the UK include limpets, sea anemones, various seaweeds and a variety of crustaceans such as the common prawn and common shore crab.

Common prawn

Common prawns can often be found in rock pools...

 

Common shore crab

...as are common shore crabs

Remember to check the tides as the most interesting pools will only be exposed at low tide and of course don’t forget your bucket and net!

George Bradford, ARKive Media Researcher

Jun 8
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World Oceans Day 2012

Since 2002, June the 8th has been celebrated as World Oceans Day, a global event coordinated by the Ocean Project and The World Ocean Network. World Oceans Day provides a chance to think about the importance of oceans to humans and celebrate these vital and inspirational bodies of water.

 

Image of whale shark filter feeding surrounded by other fish

Discovering more about the oceans can help to inspire people to take action

 

Each year World Oceans Day has a theme, and this year the theme is Youth: the Next Wave for Change. Inspiring the next generation to care about and conserve the natural world is at the very heart of ARKive. By discovering more about the oceans and their importance to our wellbeing, young people may be more likely to change their perspective and their behaviour to protect the worlds oceans.

 

Image of pink anemonefish adult with eggs almost ready to hatch

The next generation will be important advocates for the natural world

 

Get involved

All over the world there are events planned to celebrate World Oceans day from a beach festival in Florida, United States, to a plastic clean up in South Africa and responsible fish and sea-food sourcing in the UK.  Visit the World Oceans Day events page to see what events are taking place near you.

Image of common seals laying on beach

Find out what World Oceans Day events are taking place on a beach near you

 

Image of School of five-lined snapper swimming at speed

If you feel inspired by the oceans get together with friends to plan your own event for next year

It’s not too early to start planning your own event for next year. There are plenty of suggestions on the World Oceans Day website as well as advice on how to plan and market your event so it all goes swimmingly.

If you can’t make it to an event this year, you can still explore the oceans using ARKive.

However you choose to celebrate, have a brilliant World Oceans Day!

Ellie Sans, ARKive Media Researcher

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