Oct 5
Photo of barndoor skate

Barndoor skate (Dipturus laevis)

Species: Barndoor skate (Dipturus laevis)

Status: Endangered (EN)

Interesting Fact: Adult male barndoor skates have widely spaced teeth with sharply pointed cusps, but females have close-set teeth with rounded cusps.

More information:

The largest skate in the Northwest Atlantic Ocean, the barndoor skate can grow up to about 1.5 metres in length. Like other skates, this species has a flattened body which is fused to the expanded pectoral fins to form a broad disc. Its snout is pointed and its tail bears three rows of spines as well as two small dorsal fins. The barndoor skate grows slowly, taking at least 6 to 7 years to reach maturity, and can potentially live for up to 18 years. Its diet consists mainly of bottom-dwelling prey such as fish, squid, crustaceans, bivalves and worms. The eggs of the barndoor skate are laid in smooth, rectangular capsules and hatch after about 11 to 16 months.

Although not specifically targeted by fisheries, the barndoor skate has often been taken as accidental bycatch, and has been part of a group of several skates fished in U.S. waters which are not recorded by species. The flesh of this and other skates has been used as lobster bait, fish meal, pet food and seafood. The slow growth, late maturity and low reproductive rate of this species make it vulnerable to overfishing, and its population has undergone a dramatic decline. Possession of the barndoor skate in U.S. waters is now banned, and ‘no-take’ zones in areas such as Georges Bank have decreased mortality of this species and increased the number of juveniles being produced. A reduction in fishing effort is thought to have allowed the barndoor skate population to start recovering, but if fishing was to increase again the skate would be likely to decline once more.

 

Find out more about the barndoor skate at the Ichthyology Department of the Florida Museum of Natural History.

You can also find out more about the conservation of skates, rays and sharks at:

See more images of the barndoor skate on ARKive.

Liz Shaw, ARKive Text Author

Aug 30

Beyond the signature kangaroo or koala, did you know that Australia is also home to a wide range of lesser-known and somewhat bizarre-looking species such as the spotted handfish or the southern hairy-nosed wombat?  With astounding habitats including Barrow Island, the Great Barrier Reef, and the outback, we thought we would take the opportunity to highlight just some of the unique species found in this spectacular land!

Weedy wader Leafy seadragon swimming

The leafy seadragon is endemic to Australia, meaning it is found nowhere else on Earth. Living in shallow coastal waters, these slow-moving creatures call underwater seagrass meadows home, blending in perfectly due to their leaf-like appendages.

King croc

Immature saltwater crocodile swimming underwater

The largest of all crocodilians, the saltwater crocodile roams both the land and sea. By using its powerful tail and webbed hind feet, this species is an effective aquatic predator. The saltwater crocodile feasts on large land animals such as wallabies, dingoes, and even humans!

The face of climate change

Found only in northern Australia, the lemuroid ringtail possum may become Australia’s first victim of global climate change. Being unable to withstand temperatures over 86°F (30°C), this species is extremely vulnerable to heatwaves, which are expected to increase in frequency as the climate changes. In fact, a heatwave in 2005 was thought to have wiped out the entire population until a few individuals were finally discovered in 2009.

Misunderstood marsupial

Adult Tasmanian devil

Known for its frightening nocturnal screeches, the Tasmanian devil is the largest of the carnivorous marsupials. Contrary to its savage reputation, the Tasmanian devil is actually quite shy and is only aggressive when feeling threatened or when in competition with other devils.

Snack and swim

Dugong with remoras

Strictly feeding on plants, the dugong is often referred to as the ‘sea cow’, but it is actually more closely related to elephants than cows! Found off the coast of northern Australia, the dugong uses its flexible upper lip to rip whole plants apart, leaving ‘feeding trails’ on the sea floor. What a messy eater!

Water-free wallaby

Black-footed rock wallaby with young on rock

Found throughout Australia, the black-footed wallaby lives its life in groups of 10 to 100 individuals. Found primarily in rock piles and granite outcrops, this wallaby feasts mostly on grasses and fruit, and, interestingly, obtains nearly all of its water through its food.

Burrow builder

Southern hairy-nosed wombat

An expert digger, the southern hairy-nosed wombat is able to construct burrows that support a constant inside temperature of 78°F in the summer and 57.2 °F in the winter. These burrows are often formed as networks of up to thirty meters long that can host five to ten wombats.

Smooth sailing

Sugar glider on branch preparing to leap

The softly furred sugar glider uses the membrane along its body to glide distances of up to 150 feet between trees. This agile possum also has a rather distinctive alarm call, which is said to resemble a yapping dog!

Cultural croaker

Northern corroboree frog

Found only in the northern Australian Alps and the Australian Capital Territory, the northern corroboree frog has a local cultural story attached to its name. ‘Corroboree’ is an aboriginal word used to describe a gathering, where traditionally attendees are adorned with brightly colored yellow markings similar to those of this frog.

Aquatic ambler

Spotted handfish

A fish with ‘hands’ that can walk the ocean floor? It’s true! The spotted handfish, one of the world’s most endangered fish, is able to use its characteristic ‘hand-like’ fins to walk the sea floor, occasionally sucking on prey like shrimp and small fish. Threatened by development, a restricted distribution and a low reproductive rate, the spotted handfish population may be restored in the future through successful re-introduction programs.

If you’re looking to continue your ‘walkabout’ around Australia on ARKive, check out the new Barrow Island topic page or search the 1,200+ Australian species on ARKive today. Feel free to share your favorite Aussie species in the comments below!

Jade Womack, Education & Outreach Intern, Wildscreen USA

Aug 28

A significant improvement in the health of seagrass in a central Californian estuary is due to the return of sea otters, according to recent research.

Sea otter image

Researchers have found that the presence of sea otters may be improving the health of seagrass beds

Seagrass decline

Seagrass has been suffering drastic declines worldwide, and coastal California is no exception. Urbanisation has led to a massive increase in nutrient pollution along the state’s coast, with run-off from fields treated with nitrogen-rich fertilisers being blamed for the reduction in seagrass beds in the region. However, new research has revealed that the return of sea otter populations to the area may be enabling seagrass levels to recover.

Sea otters were hunted to near extinction in the late 19th and early 20th centuries, mainly for their dense pelt which was extremely sought-after for the fur trade. This latest research, published in the journal Proceedings of the National Academy of Sciences (PNAS), suggests that the drastic reduction in sea otter numbers may have exacerbated the decline of seagrass in the region.

Sea otters are now returning to the area, and, despite the continued pollution of the ocean, the water-dwelling plants are now doing much better. It is thought that the return of sea otters has triggered a complex ecological chain reaction which favours the survival of seagrass.

Sea otter feeding image

Sea otters feed on crabs and other shellfish

Seagrass saviour

Scientists assessed seagrass levels in part of Monterey Bay, California, over the past 50 years, mapping increases and declines. A whole host of factors which could potentially affect seagrass levels were studied, but the only one which matched the recorded changes was sea otter numbers. The health of the marine ecosystem relies upon a delicate balance of predator and prey species, and scientists have theorised that it is a readjustment in this balance that is now enabling seagrass to thrive.

Increased nutrients in the ocean due to fertiliser run-off have favoured the growth of a particular type of algae which grows on seagrass, shading the leaves and causing them to die off. Ordinarily, this algae is kept in check by small invertebrates which feed upon it, but with the reduction in sea otters came an increase in one of its main food sources – crabs. Crabs feed on marine invertebrates, so higher numbers of crabs meant fewer invertebrates to keep algae levels down, therefore contributing to the drastic reduction in seagrass.

Testing the hypothesis

To test their theory, the researchers set up experiments in similar estuaries with and without sea otters, and carried out other tests in the field as well as in the lab. One experiment involved putting cages on the seagrass, with some being accessible to sea otters and some not. The results of the tests confirmed the hypothesis.

Sea otter image

Sea otters

Fighting climate change

Brent Hughes, lead author of the study, described seagrass as being ‘the canary in the coalmine’, as it can be used to predict the levels of nutrient pollution in the water. He marvelled at the positive effect the return of the sea otters is having, saying, “This estuary is part of one of the most polluted systems in the entire world, but you can still get this healthy thriving habitat, and it’s all because of the sea otters. So it’s almost like these sea otters are fighting the effects of poor water quality.”

Seagrass plays an extremely important role in the marine ecosystem, acting as a nursery habitat for a wide variety of fish species, and taking in carbon dioxide from the water and the atmosphere, therefore potentially helping in the fight against climate change. In addition to this, seagrass contributes to the stability and protection of the shoreline.

It’s what we call a foundation species, like kelp forest, salt marsh or coral reef,” said Hughes. “The major problem from a global perspective is that seagrass is declining worldwide. And one of the major drivers of this decline has been nutrient inputs from anthropogenic sources, via agriculture or urban runoff.”

Benefits

A ban on sea otters that was in place to prevent them from impinging on fisheries in the southern California area was lifted last year, and so the findings from this latest research are particularly relevant.

That’s important because there’s a lot of these kind of degraded estuaries in southern California because of all the urban runoff from places like Los Angeles and San Diego,” said Hughes. “Coastal managers will now have a better sense of what’s going to happen when sea otters move into their systems. There’s a huge potential benefit to sea otters returning to these estuaries, and into these seagrass beds that might be threatened.”

Read more on this story at BBC News – Sea otter return boosts ailing seagrass in California.

See more photos and videos of sea otters on ARKive.

Learn more about the importance of food chains and food webs in our exciting Web of Wildlife education resource.

 

Kathryn Pintus, ARKive Text Author

Aug 8

As Shark Week continues to float on here in the US, we think it’s the perfect time to shine the spotlight on some of the strangest-looking sharks found on Earth. We all know what the great white shark looks like but have you seen a shark with an ‘executioner’ style hood over its head or one with a beard? Read on to see how many of these bizarre sharks are new to you!

 10. Trendy trim

Photo of leopard shark swimming along sea bed

With a chic patterning of splotches over its body, the leopard shark roams the ocean in the day and night. Despite the fear that all sharks are dangerous, the leopard shark is actually harmless to man and even approachable when it lounges on the sea floor during the day.

 9.  An immense encounter

Photo of whale shark filter feeding, surrounded by other smaller fish

We think this shark merits an appearance on this list just for its sheer size. The largest fish in the sea, the whale shark can weigh up to 13 tons. Perhaps ironically, the biggest fish in the world feeds primarily on some of the smallest organisms, tiny planktonic organisms.

8.  Hard-headed

Photo of kitefin shark swimming

The blunt snout of this species along with its large eyes makes the kitefin shark a perfect addition to our list. The kitefin shark is uniquely ovoviviparous meaning it gives birth to live young instead of laying eggs like most other fish species.

7. Hooded hider

Photo of hooded carpetshark showing spriacle

With a black mask over its head and snout, the hooded carpet shark is said to resemble an eerie ‘executioner’s hood’. The addition of white spots that cover most of its body helps this species to blend into surrounding coral until this nocturnal shark comes to life at night.

6. Wide-eyed wonder

Photo of crocodile shark speciman close up

Check out the blinders on this fish! The crocodile shark is a small slender shark known for its short head and large eyes likely used to hunt effectively at night. Following its prey towards the water surface at night and away during the day, the crocodile shark is an active hunter which enjoys a wide variety of prey including squid, fish, and shrimp.

5. See a saw

Photo of green sawfish swimming

Aptly named, the green sawfish has an elongated snout with over 23 pairs of teeth.  By using this impeccable nozzle, the green sawfish is able to feed on slow-moving fish by clubbing at them with a side of its saw. Cleverly, the green sawfish uses its saw to act as a shovel-like instrument to rake out crustaceans.

4. Face of an angel

Photo of angel shark on the seabed at night

Sometimes mistaken for a large ray due to its appearance, the angel shark has a remarkably flat body and well-placed eyes on the top of its head that are perfect for ambush-style predation. The angel shark is Critically Endangered, likely due to its prevalence in by-catch – the accidental capture of species through standard fishing practices such as trawling. Sadly, this species has been declared extinct in the North Sea.

3. Mega mouth

Photo of basking shark feeding

As the second largest fish in the sea, the basking shark is one to impress. Perhaps a good kisser, the basking shark uses its three-foot-wide mouth to filter feed while it ‘basks’. Not too interested in the social scene, the solitary basking shark is thought to hibernate in deep water.

2. Ancient allure

Photo of filled shark swimming

The frilled shark is one of the most primitive species of living shark. Having perfected its look to have a lizard-like, blunt-ended snout and a very large mouth, the frilled shark possesses an unconventional beauty. Living primarily in the deep-water darkness, this three-foot-long and mysterious beast has had few observations made in its natural environment.

1. Camouflaged charmer

Photo of tasselled wobbegong

Literally meaning ‘well fringed nose with shaggy beard’, the tasselled wobbegong is an exceedingly unusual looking shark. With its branching skin flaps and a lofty lattice-like ‘beard’ the wobbegong’s bristles provide it with a sagacious camouflage and overall appearance. We challenge you to find a weirder-looking shark on ARKive!

Were any sharks on our list new to you? Or do you have a favorite to add to the list? Surf the ARKive site for more sharks and share your favorites in the comments below!

Jade Womack, Education & Outreach Intern, Wildscreen USA

Jul 27
Photo of Balearic shearwater in flight

Balearic shearwater (Puffinus mauretanicus)

Species: Balearic shearwater (Puffinus mauretanicus)

Status: Critically Endangered (CR)

Interesting Fact: Like other shearwaters, the Balearic shearwater is named for its ‘shearing’ flight, in which it flies with stiffly held wings just centimetres above the ocean waves.

Considered to be the most threatened seabird in the Mediterranean, the Balearic shearwater is a medium-sized shearwater which breeds only on the Balearic Islands, in the western Mediterranean Sea. This species spends most of its time out at sea, where it dives into the water to catch fish and squid, using its long, sharp beak to capture its slippery prey. The Balearic shearwater returns to land to breed between February and June, and each pair lays a single large egg, usually in a small cave, cavity or under a boulder. Breeding pairs may remain together for many years. At the end of the breeding season, some Balearic shearwaters migrate northwards to winter in the Bay of Biscay, and may reach as far north as the United Kingdom and Scandinavia.

The main threats to the Balearic shearwater include predation by introduced mammals and entanglement in fishing gear. The breeding habitat of this species is threatened by urbanisation and by introduced rabbits, which compete with the birds for nesting sites, and the Balearic shearwater may also be negatively affected by pollution, oil spills and a reduction in prey abundance. As part of a recovery plan in place for the Balearic shearwater, rats have been eradicated from a number of breeding sites and a number of protected areas have been created. Studies into the species’ biology and populations are also being carried out. Efforts are underway to assess the problem of bycatch in fisheries, and awareness campaigns, together with mitigation measures, will be important in addressing this threat.

Find out more about seabird conservation at the BirdLife International Global Seabird Programme.

You can also read more about UK marine species in our National Marine Week guest blog.

See images of the Balearic shearwater on ARKive.

Liz Shaw, ARKive Text Author

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