If you've ever seen a clip of a seal being ambushed by a great white you might understand why they only sleep with one half of their brain at a time. With enemies like The Man in the Gray Suit it's always advisable to maintain at least a marginal degree of 'round-the-clock alertness.
A new study led by scientists at UCLA and the University of Toronto, and published in the February Journal of Neuroscience, investigated this phenomenon of half-brain sleeping.
"Seals do something biologically amazing — they sleep with half their brain at a time. The left side of their brain can sleep while the right side stays awake. Seals sleep this way while they're in water, but they sleep like humans while on land. Our research may explain how this unique biological phenomenon happens," said Professor John Peever of the University of Toronto.
The researchers found higher levels of an important brain chemical, acetylcholine, in the waking halves of the seal brains than the sleeping halves. The discovery could aid in the understanding of human sleep disorders, the study's senior author Jerome Siegel of UCLA's Brain Research Institute claims.
"About 40% of North Americans suffer from sleep problems and understanding which brain chemicals function to keep us awake or asleep is a major scientific advance. It could help solve the mystery of how and why we sleep."
Sleep tight seals, and don't let the great white sharks bite.
There’s a new estimate for how many sharks are killed each year by fishermen worldwide and the news is grim. Despite growing awareness of the threat sharks face and legislative efforts around the globe to stem the unsustainable harvest of sharks, a new study published this week in Marine Policy puts the number slaughtered each year at 100 million sharks, or three sharks caught per second.
Due to the incomplete nature of the data for shark catches, that number could be as low as 63 million or as high as 273 million, but both the high and low end estimates are outside of safe biological limits. According to the study’s authors, this number represents approximately 7% of all sharks in the ocean. On average, shark populations can grow at a maximum rate of 5% per year. As can be seen, shark populations cannot grow fast enough to sustain this enormous removal each year, which is why sharks numbers have declined so dramatically in recent years.
The primary culprit for this staggering level of exploitation remains the same: overfishing and bycatch, driven by the unabated demand for shark fin soup, the consumption of which is seen as a status symbol in China. The fin itself is a largely flavorless component of the soup and provides no additional nutritional value.
Sharks are especially vulnerable to overfishing due to their slow growth, late maturation and small litters, with biological life histories that more closely resemble large mammals than other fish. Some sharks, like the Atlantic Ocean's dusky shark, do not mature until as late as 21 years of age and give birth to as few as three pups every three years.
Oceana is fighting to protect sharks around the world. Learn more about what we do.
On February 8, Oceana and National Geographic launched an expedition to explore the waters off of the remote Desventuradas Islands more than 500 miles off the coast of Chile. By documenting marine life and habitat the team hopes to persuade the Chilean government to protect more than 60,000 miles surroundinig this archipelago. Below is an expedition journal entry from Enric Sala, National Geographic Explorer-in-Residence. Click here to view all Desventuradas Expedition blog posts on National Geographic's Explorers Journal.
19 February 2013
When we think of predators, our minds often picture large animals with sharp teeth and scary faces, animals that have evolved just to kill humans. Our collective memory makes us fearful of the night, and almost everyone has been startled by unknown noises in a dark forest. This fear has been engraved in our collective unconscious like carvings in a rock. When it comes to the ocean, many people still fear sharks (despite repeated evidence that sharks are the ones who should be scared of us) or deep alien creatures that hide in the darkness to attack unexpectedly.
The top predator at the Desventuradas is not the typical reef shark, or a grouper with a huge mouth able to swallow a diver. It is not a fearsome animal that kills at night either. The largest predator here is the Juan Fernández sea lion (Arctocephalus philippi), the cutest carnivore we have found in any of our Pristine Seas Expeditions to date. They spend much of the day hanging out on rocky platforms near the water. When we approach them, it’s like someone brought free candy to a school. The sea lions raise their heads, get indeed very excited, and drag their fat bellies from rock to rock until they jump in the water.
The Juan Fernández sea lion is the cutest carnivore we have found in any of our Pristine Expeditions to date. (Photo by Enric Sala)
Underwater, the sea lions become torpedoes of enormous grace and elegance. Their eyes are large as a Japanese cartoon character’s, and their looks pierce us as they swim very fast between us divers. After playing with our bubbles and checking us out very closely, they just hang out, their backsides on the surface and their heads hanging down like bats.
While things look bleak for cod populations in the United States, particularly on Georges Bank and in the Gulf of Maine where late last month regulators slashed quotas for these beleaguered stocks, cod off of Norway and Russia are providing an encouraging example of the fish’s resilience when managed wisely.
As Reuters reports this week, fishermen in the far north are enjoying a boom in cod fishing where “the quota off northern Norway and Russia is a record 1.02 million metric tonnes, up a third from 2012 and six times as high as in 1990.”
The article credits both global warming for expanding the fish’s range northwards, but also the strict management of quotas issued from Oslo and Moscow.
Two and a half hours west of Key West by boat is lonely Fort Jefferson, a Civil War-era fort marooned in the middle of the Gulf of Mexico and encrusted in coral reefs. Here the color of the water ranges from cerulean to toothpaste-aquamarine as magnificent frigatebirds, masked boobies, and sooty terns haunt the coral-white beaches of this unfinished garrison, a former prison for union army deserters.
One of seven islands that make up the Dry Tortugas (so named for their lack of water and wealth of turtles at the time of Ponce de Leon’s discovery in 1513) Fort Jefferson is a monument to the ingenuity and industry of engineers and masons who slogged bricks from as far as Brewer, Maine, to the middle of the ocean to construct a fort that has survived in the crosshairs of two centuries of hurricanes. Now, the park is also a monument to the scientific principles of ecosystem management, proof that protecting habitat benefits all—environmentalists and fishermen alike.
In 2001, over the objections of local fishermen, the National Marine Fisheries Service (NMFS) announced that it would establish a 151-square nautical mile no-take zone in the area—the Tortugas Ecological Reserve. It was assumed that closing the well-known grouper and snapper spawning grounds of the Dry Tortugas to fishing would hurt the industry’s bottom line.
But that didn’t happen. The fish got bigger. And there were more of them.
On Friday Oceana and National Geographic launched an expedition to explore the waters off of the remote Desventuradas Islands more than 500 miles off the coast of Chile. Already the team is sending back fascinating footage. Below is an expedition journal entry from Enric Sala, National Geographic Explorer-in-Residence. Click here to view all Desventuradas Expedition blog posts on National Geographic's Explorers Journal.
10 February 2013
Today we did the first scientific dives reported for San Ambrosio Island. We don’t even know if anyone has ever dived here, period. The sea was calm, the water blue and clear, and we could not wait to jump in the water.
It has been almost a year since Alex Muñoz – Executive Director of Oceana Chile – and I started planning this expedition. During this time, we were not able to find a single underwater photo of the Desventuradas Islands. So I felt like I was parachuting in, at night, over unknown territory. I had no idea what I was going to find, but this only made it more exciting. Because these islands are so remote and apparently devoid of local human impacts, we expected to see lots of fish–and hopefully large fish in particular.
Whale watchers off of Dana Point, California were treated to an exhilarating sight this weekend, witnessing a spectacular if unusual phenomenon: the so-called dolphin stampede.
All at once a massive pod of 1,000 dolphins turned the waters around Capt. Dave's Dolphin and Whale Safari boat white, seemingly engaged in one one observer described as a "race", at times topping 25 mph. While the sight of a dolphin stampede is extremely rare, tours by this operator encountered the phenomenon twice this weekend, once on Saturday and once on Sunday.
It is unknown why the dolphins "stampede" or what prompts the bizarre but breathtaking behavior.
For the past three years, whales and dolphins in the Gulf of Mexico have been undergoing what the National Marine Fisheries Service (NMFS) is calling an “unusual mortality event”—that is, they have been stranding and dying off by the hundreds (817 in all), and no one knows why. The Deepwater Horizon catastrophe provides a likely explanation, but, in fact, 114 marine mammals died in 2010 even before the devastation of the oil spill had even begun.
It could have something to do with a bacterial infection, known as brucellosis, revealed in some animal necropsies, or it could be related to environmental degradation, climate change, fishing activity, or the cumulative effects of all these combined stressors. Or, it could largely be a natural phenomenon merely exacerbated by anthropogenic impacts (though unlikely). It is truly a mystery.
What is less mysterious is the cause of death for three of the most recent dolphin victims. In the past six months, two bottlenose dolphins washed ashore, one in Louisiana and one in Mississippi, with gunshot wounds to their heads. In Alabama, another live dolphin was discovered stabbed in the head with a screwdriver. Though it initially survived this brutality, the dolphin eventually succumbed to its injuries and died. NOAA is currently investigating these cases and asks anyone with any information to call their Office of Law Enforcement hotline at 1-800-853-1964. Penalties under the Marine Mammal Protection Act range up to $100,000 in fines and up to one year in jail per violation.
Kudos to a team of divers off the coast of Mexico who rescued a pregnant whale shark from near-certain death after the gentle giant became entangled and trapped in a thick rope some 90 feet underwater.
The divers were accompanying a group of tourists off of Roca Partida, a remote volcanic outcrop that is part of the Revillagigedo Islands 250 miles Southwest of Cabo San Lucas, when they discovered the 33-foot 15-ton animal. After the animal was cut loose it showed deep scars where the rope had cut into its back and fins.
Despite their massive size (they are the world’s biggest fish and their mouths are large enough to fit a human inside) whale sharks are docile filter feeders, gulping down huge quantities of plankton, small fish and krill.
It is difficult to describe the ocean's vastness and variety of life, but that is exactly what some researchers have tried to do. In a study released this week, and carried out with the help of 270 taxonomists from 32 countries, researchers put the likely total for the world's marine species at a tidy million species, only a third of which are known to science. Scientists arrived at the million figure by extrapolating from the rate of discovery of new species and by projecting from sampled areas of the ocean.
Of the roughly 230,000 species that have been described there are 200,000 animal, 7,600 plants, 19,500 diatoms, kelps and red algae known as chromista, 550 protists and 1,050 fungi (the study did not include bacteria, viruses or archaea). But even those species that are known can prove amazingly elusive. Last week scientists announced that a spade-tooth beaked whale and calf that washed ashore in New Zealand were the first such animals ever seen (what was known about the animal previously had come from skull fragments).
Hundreds of thousands more species await discovery.
What is your favorite species? is it the spanish dancer, the longnose sawshark, the pineapplefish? Check out our marine wildlife encyclopedia to learn more about just some of the million species of living beings in our oceans.