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Why does the thresher shark have such a large tail?

Tresher shark

The long caudal fin has puzzled marine biologists, since it has been difficult to see any use for this enlarged fin. Recent research has however unveiled that the sharks’ tail seems to play a vital role when the thresher shark hunt small prey fish. Thanks to its large tail, the thresher shark can easily swat and stun small fish in the water. This is probably also why thresher sharks often get their tails caught in long-line fishing equipment baited with small fish – the sharks are trying to stun the bait but end up captured instead.

The new findings doesn’t come as a surprise; there is for instance a report dating back to 1923 in which a thresher shark is described using its tail to catch food. The new study is however the first one to show exactly how it works.

The research, headed by Dr Chugey Sepulveda, has been carried out by biologist from The Pfleger Institute of Environmental Research in Oceanside, California, USA and the University of Massachusetts in Dartmouth.

While filming hunting sharks in the ocean, the research team was able to identify two distinct techniques for stunning prey. The thresher shark could waggle its body and surge forward, effectively forming a wave down its body ending in a tail flick, or the shark could simply position itself alongside the prey and make a sideways strike.

The common thresher is for now, the only species that this feeding behaviour has been documented for. But we hypothesise that all three actively pursue prey with their elongate caudal fins,” said Dr Sepulveda.

There are three species of thresher shark:

  • Common thresher (Alopias vulpinus)
  • Pelagic thresher (Alopias pelagicus)
  • Bigeye thresher (Alopias superciliosus)

The thresher shark study has been published in Journal of Fish Biology.

http://www3.interscience.wiley.com/journal/118483233/home?CRETRY=1&SRETRY=0

The research was supported by the National Science Foundation, the George T. Pfleger Foundation, the William H. and Mattie Wattis Harris Foundation, and the National Oceanic and Atmospheric Administration Bycatch Reduction and Engineering Program.

Cloudy with a chance of fish

Fish raining down on you from the sky is rare, but fish raining down on you two nights in a row is just plain eldritch. The unlikely two-night fish rain occurred last week in a small Australian town called Lajamanu in the Northern Territory.

On Thursday around 6 pm hundreds of small white fish started falling from the sky, to the shock and surprise of the local inhabitants who live on the edge of the Tanami Desert, hundreds of kilometers from Lake Argyle and Lake Elliot and even further away from the ocean. To make things even more bewildering, the same thing happened around 6 pm on Friday as well.

Christine Balmer, an aged care co-ordinator working at the Lajamanu Aged Care Centre, said her family interstate thought she had lost the plot when she told them about the event.

“I haven’t lost my marbles,” she said to local media. “Thank god it didn’t rain crocodiles.”
Balmer also managed to snap some photos of the fish littering the ground.

“They fell from the sky everywhere”, she explained. “Locals were picking them up off the footy oval and on the ground everywhere. These fish were alive when they hit the ground.”

Lajamanu has a population of less than 700 people, of which a significant amount are of Aboriginal origin. Its only accessible by air or dirt road and governed by a combination of community government council and local tribal council.

The town is no stranger to fish rains. Back in 2004 Lajamanu experienced a similar downpour and there are also reports of fish falling from the sky in 1974. This is however the first recorded incident of fish raining down on Lajamanu two evenings in a row.

Fish rains are normally caused by tornadoes that sweep up fish, and fish captured in this fashion can travel far distances and still be alive when they land.

According to Ashley Patterson, senior forecaster at the weather bureau, conditions were perfect on Friday for a tornado in the Douglas Daly region. However, no tornadoes has been reported to the authority.

“It’s a very unusual event,” he said. “With an updraft, (fish and water picked up) could get up high – up to 60,000 or 70,000 feet. Or possibly from a tornado over a large water body – but we haven’t had any reports.”

The small white fish has been tentatively identified as spangled perch (Leiopotherapon unicolor ), one of the most widely distributed Australian native freshwater fishes.

Dead fish are covering the beaches of Brazil

Massive amounts of dead fish are covering the beaches of Brazil and roughly 80 tonnes (175 000 lbs) have been removed from the iconic Ipanema beach in Rio de Janeiro.

The mass death, which seems to have occurred at sea right before the weekend, remains unexplained. Over 100 people are currently trying to rid a 4.5 square kilometer area from rotting fish carcases.
Environmental experts in Rio de Janeiro have suggested that the mass death might be caused by marine algae. The deaths are not limited to any specific species of family of fish.

Whales weren’t the first giant filter-feeders in the sea

Newly investigated fossils show that a type of filter-feeding fishes that aren’t closely related to today’s whales (who, of course, are mammals and not fishes) roamed the oceans during the Mesozoic Era some 170 million years ago. Previously the whales were believed to have been the first large filter feeders, but these new fossils tell a different story. See pictures here

The giant filter feeders, which have been given the name Pachycormiforms, died out at the same time as the dinosaurs. Eventually sharks began filling the vacant ecological niche some 56 million years ago, followed by modern cetaceans such as whales roughly 22 million years later.

The Pachycormiform fossils have been investigated by a team of researchers* led by University of Oxford scientist Matt Friedman, as a part of a study where both old and new fish fossils from England, Japan and the USA have been put under scrutiny. The article has been published in the journal Science.

Some of these fishes were true giants in the world of bony fishes, such as the 6 meter (20 feet) long Bonnerichthys that inhabited a seaway covering what is today the state of Kansas, USA.

A previously described species, Leedsichthys, from the Jurassic of Europe that belongs to the same lineage that includes Bonnerichthys was even larger, likely reaching up to about 30 feet, which is the most massive bony fish of all time,” said Kenshu Shimada, co-author of the article and professor in the Environmental Science Program at DePaul University.

Bonnerichthys was first believed to have been similar to a swordfish, with numerous fang-like teeth.

However, our close examination of the specimen showed that such a long snout and fang-like teeth were not present in the fish,” Shimada said. “Rather, with a blunt massive head, the fish had long toothless jawbones and long gill-supporting bones that are characteristic of plankton-feeding fishes.”

http://www.sciencemag.org

*– Matt Friedman, Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK.

– Kenshu Shimada, Environmental Science Program and Department of Biological Sciences, DePaul University, 2325 North Clifton Avenue, Chicago, IL 60614, USA, and Sternberg Museum of Natural History, Fort Hays State University, 3000 Sternberg Drive, Hays, KS 67601, USA.

– Larry D. Martin, Natural History Museum and Biodiversity Research Center, University of Kansas, 1345 Jayhawk Boulevard, Lawrence, KS 66045, USA.

– Michael J. Everhart, Sternberg Museum of Natural History, Fort Hays State University, 3000 Sternberg Drive, Hays, KS 67601, USA.

Jeff Liston,Division of Ecology and Evolutionary Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK.

– Anthony Maltese, Triebold Paleontology and Rocky Mountain Dinosaur Resource Center, 201 South Fairview Street, Woodland Park, CO 80863, USA.

– Michael Triebold, Triebold Paleontology and Rocky Mountain Dinosaur Resource Center, 201 South Fairview Street, Woodland Park, CO 80863, USA.

Python-hunting season coming up

PythonThe Florida Fish and Wildlife Conservation Commission (FWC) has declared March 8 through April 17 hunting season for Burmese pythons living on state lands in South Florida.

If you wish to hunt pythons, you’ll need a hunting license and you must also purchase a $26 management area permit for reptiles. Centerfire rifles mustn’t be used, but shotguns, pistols and ordinary rifles will be permitted. All kills must be reported to FWC within 36 hours.

You will not be allowed to remove living pythons from state lands.

The Burmese Python (Python molurus bivittatus) is the largest subspecies of the Indian Python and is native to south and south-eastern Asia. During recent years populations of Burmese Python has managed to establish themselves in Everglades, Florida. Since the python is a popular pet, these feral snakes are believed to hail from pets set free by their owners, e.g. because the snakes grew too large to handle or expensive to feed. Hurricane Andrew also released an unknown number of pets, including exotic fish and reptiles, into the wild when it wrecked havoc with homes and establishments along the coast back in 1992.

Over 1300 Burmese Pythons have been captured in the Everglades so far and local authorities now feel that it’s time to enlist civilians in the struggle against this invasive species. The Burmese python competes with the native alligator for food and is also known to eat birds, including several endangered species. Although the alligators seem to fend off the pythons pretty well, it is impossible to tell what long-term effects the introduction of such an efficient top-predator could have on the unique ecosystem of the Everglades.

FWC official Chuck Collins said government isn’t always the best solution to stopping the spread of invasive, exotic species.

Better solutions are developed when we work with people closest to the issue — in this case, the hunters,” Collins said.

Roughly 50 hunters have already participated in ”Pythons 101” courses arranged by FWC officers and local experts, courses where hunters get to know more about python behavior, biology, habitat and diet as well as capture techniques and how to handle a python in safe way. The participants were also offered a chance to practice in the L-67 canal system.

The quickest and easiest way to euthanize them is with a sharp instrument like a machete,” said Cole, a snake breeder from Haines City who instructed the hunters to kill rapidly and cause as little stress and suffering as possible. “The veterinary association recommends swift decapitation or a bullet. Don’t club these snakes to death”, he added.

The Burmese python is a semi-aquatic species that likes to stay near water but it can also be encountered in trees. Wild individuals normally stay below 4 meters in length but large specimens are nearly 6 meters long. Within its local range it is a popular source of food and Burmese python parts are also utilized by traditional healers.

Rarely seen deep-dweller caught on tape by remotely operated vehicle

The huge oarfish has been filmed by scientists operating a tiny submarine by remote. This may be the first time this fish is filmed, or even seen, in its natural environment. The species might have been caught on camera at a depth of 765 meters during a research mission off the coast of western African in 2007, but marine experts haven’t been able to positively identify the creature in that video.

Oarfish are large, elongated fishes belonging to the family Regalecidae. The family contains four species of which the largest one is the famous King of Herrings (Regalecus glesne), listed in the Guinness Book of World Records as the longest bony fish alive today. The largest known King of Herring was 17 metres (56 ft) in lenght.

Normally, this deep-dweller is only encountered when dead ones are washed ashore or when dying specimens are brought up to the surface by fishermen.

The research crew was therefore happily surprised when an oarfish suddenly showed up in front of their camera.

We saw this bright vertical shiny thing, I said ‘are they lowering more riser?’ as it looked like they were lowering a huge pipe,” said Mark Benfield from Louisiana State University, Baton Rouge, USA, one of the scientists working at the Serpent Project in the Gulf of Mexico.”We zoomed in a little bit and we said ‘that’s not a riser that’s a fish!’ As we approached it retreated downwards swimming tail first in a vertical orientation as the ROV followed. What was interesting about the fish was its swimming behaviour. It moved by undulating its dorsal fin in waves that propelled it backwards at quite a good speed.”

Early estimates measure the fish at between 5m and 10m in length, which roughly equals 16-33 feet.

The Serpent Project is a collaboration between marine researchers and energy companies such as Petrobras, Chevron and Shell and involves the use of remotely operated vehicles (ROV’s) to explore depths to which it would be extremely dangerous to send a human. Responsible for the project is the National Oceanography Centre in Southampton, USA.

The King of Herrings is believed to be the creature behind the ancient myths about gigantic sea serpents. It has a prominent dorsal fin, almost like the continous spikes of a fairytale dragon.

Spitting fish learn to catch artificial flies

archerfishIn south-east Asia and northern Australia, Archer fish can be seen spitting jets of water up to three meters to knock out insects and spiders and make them fall into the water. Archer fish does for instnace help control the populations of mosquitoes and flies.

In captivity, insects in the air can be scarce – especially during the chilly Bristol winter. That is why a shoal of archer fish living at Bristol’s Blue Reef Aquarium have been given a mobile dotted with plastic flies for target practise.

The archers living in the aquarium are roughly 1.5 years of age and staff said that their natural hunting instinct may have become rusty. To combat this, the staff is now smearing the fake flies with bloddworm so that when a fish manages to hit a fly, tasty bloodworm falls down into the water.

In the summer if we have some insects flying around I’ll be surprised if they don’t go for them,” said senior aquarist Lindsay Holloway.

Funny looking fish found in Chinese mountain cave

weird fishResidents of the Daluo village in China’s Guangxi province have caught several weird looking yellow fishes in a cave lake located 1,000 meters (3,280 feet) below ground.

Experts working at the Bama County and Guangxi provincial aquatics institutes have been unable to indentify the fish, which sports a flat mouth shaped almost like the bill of a duck and eye-catching red lips. The mysterious creature is also adorned with a long, slim “moustache”.

According to Li Zuneng, head of the village, members of his community have heard stories about this outlandish fish told by the oldest villagers, but many had assumed that it was some type of fairytale creature. Up until now, no one from the younger generations had actually seen the deep dweller.

The cave where the fish lives is named Fu Yuan Dong, which means Cave of Fortune.

King demoiselle turns out to be three species, not one

A recent study has unveiled that the King demoiselle (Chrysiptera rex) is actually three different species that recently diverged from each other.  (picture)

This work, along with others, is starting to show that there is a lot more biodiversity in the oceans then we previously thought,” said Joshua Drew, a marine conservation biologist at the Field Museum of Natural History in Chicago and a member of the demoiselle study. “We really are in a situation where we are losing things before we even know they exist.”

The King demoiselle comes in a wide range of colours and patterns, but this alone is not enough to consider it several species. There are plenty of examples of fish that look very dissimilar from each other while still belonging to the same species.

However, what Dews’ colleagues discovered while doing field research in Southeast Asia was that the differences in appearance seemed to be linked to distinct geographical regions. In order to find out more, they decided to ship about a dozen King demoiselle samples to Drew, collected from three separate populations in Indonesia, the Philippines and the South China Sea.

In his laboratory, Drew analyzed the genetic composition of the samples, focusing on three different genes – one that has evolved slowly and two that have changed quickly over the years. What Drew found out was highly interesting: the two fast changing genes differed in the three geographical groups, but not the one slow changing one. This indicates that from an evolutionary perspective, the three groups diverged from each other quite recently.

That means that this little fish we thought was broadly distributed has a mosaic of individual populations and each one is genetically distinct,” Drew explained. “That highlights how little we really know about how biodiversity on Earth is distributed.”

Earlier, scientists assumed that it was difficult for distinct populations of reef fish to form if they had small larvae easily caught by currents. It seemed reasonable to presume that larvae from many different geographical locations would intermingle with each other throughout the sea. New data, obtained from studies like the King demoiselle one, do however suggest that larvae often settle close to its point of origin.

The King demoiselle study will be published in the journal Coral Reefs.

http://springerlink.metapress.com/content/100407/?p=32f929fa7f60452da6d63226ec8898a6&pi=0

Swedish vacationer killed by jellyfish in Malaysia

A Swedish woman vacationing with her family in Langkawi, Malaysia was killed by a jellyfish while bathing off the coast of Pantai Cenang.

Carina Löfgren was on her way back to the beach when she encountered the dangerous jellyfish just a few meters from the shore.

Carina was walking roughly one meter in front of me,” her husband Ronny Löfgren told Swedish newspaper Aftonbladet. “It wasn’t deep; the water barely reached my trunks. Suddenly she started screaming violently and grasp at her legs. It made us realise that it was some kind of stinging jellyfish. We tried to remove the tentacles from her. It took four to five seconds, then she collapsed.”

Carina was dragged out of the water and her brother, who used to work as an emergency first responder, administered first aid with heart compressions and mouth-to-mouth.

He administered CPR for four or five minutes”, Ronny Löfgren explained. “Then I replaced him. But I instantly felt that she was lifeless. She died in my arms.”

The ambulance reached the beach after 15 minutes. According to Ronny Löfgren they immediately understood that they could do nothing to help Carina at this point.

One of them said ‘ah, jellyfish’ and shook his head. They tried to revive her for half a minute. Then they shook their heads again.”

Box Jellyfish

Box jellyfish are a group of invertebrates belonging to the class Cubozoa. One of the most dangerous members of this group is Chironex fleckeri, also known as the Sea wasp. Chironex fleckeri is found in the oceans of Australia and southeastern Asia and an average specimen contains enough venom to kill 60 adult humans.

They can be very small and transparent which makes them difficult to spot”, says Swedish marine biologist Lars Hernroth. “Heart failure is the most common cause of death when stung by a sea wasp. In most cases, it happens extremely fast. The overall health condition of the victim will in part determine the victims’ resilience towards the venom.”

Hernroth believes it is important to ask local tourist information agencies about the jellyfish situation in the area. Some popular holiday destinations places nets in the water to catch jellyfish, but it will only work against the big ones – the small ones will slip through.

Swimmers stung by Chironex fleckeri often fail to make it back to the shore; they die from drowning or cardiac arrest within minutes. If a person does make it back he or she will be in need of immediate treatment, and even with proper treatment, fatalities are common. While administering first aid, make sure that some calls an ambulance. Chironex fleckeri antivenom does exist, but must be administered quickly. In areas where Chironex fleckeri is common, ambulances often carry antivenom – at least in developed parts of the world.