Blogs / 80beats

Cleaner fish have a pretty good little business going. These select species of small underwater inhabitants set up “cleaning stations” where they eat parasites and dead tissue off larger fish. Sure, it might not be a gourmet meal, but in exchange for the service the large fish don’t eat the cleaners.

In some cases a pair of fish work in tandem, and a new study has found that males will punish their female partners if the females go overboard and eat more of the client than they should. While the research shows that fish, like people, can be aggrieved on behalf of a third party, don’t be too impressed with the males’ altruism—they get plenty out of the deal.

For a study in Science, researchers looked at the fish Labroides dimidiatus, whose females usually play by the rules of the cleaning business. But the females can sometimes be too greedy and “bite the flesh of the fish they are cleaning in a bid to get to the mucus, which is more tasty than the parasites on the surface,” researcher Redouan Bshary found. The male fishes, which are bigger in size, would then step in to chase the females away [AFP].

(more…)

Sushi lovers, we’ve got some bad news. For a study that came out in PLoS One, researchers ordered sushi at restaurants across New York City and Denver, Colorado, and found that an alarming percentage wasn’t made from the fish it was advertised to be. More than half of the eateries weren’t completely clear and honest about the fish they offered, the study says. Some even mistakenly served up escolar, which can give people diarrhea and stomach problems.

Although their results were shocking, exposing sloppy sushi joints wasn’t their main goal. The scientists were trying to improve on a new species-identification technique, called DNA barcoding…. Their goal is to build a catalog of every fish species on earth so that anyone with a handheld DNA reader could definitively identify fish within minutes [Wired.com].

One reason researchers investigated sushi is that so much of it has been made from endangered species like the bluefin tuna. In the restaurants that lead scientist George Amato checked out, the device showed 25 percent of what was labeled as tuna on sushi menus was bluefin, Amato said. The device also has been used to identify the presence of endangered whales in Asian markets and fraud in the labeling of caviar and red snapper [UPI].

This study comes in the wake of an international ruling that reduces the quota for bluefin catch from 22,000 metric tons annually to 13,500 for 2010. But that isn’t enough for many environmentalists, nor for The New York Times editorial board, which this weekend called for the United States to list bluefin under the Convention on International Trade in Endangered Species. The law effectively bars commercial trade in any listed species, and has been helpful in protecting other animals like elephants and whales [The New York Times].

Related Content:
80beats: Scientists Say Ban Atlantic Bluefin Tuna Trade—And Sushi Chefs Shudder
80beats: Documentary on Endangered Bluefin Tuna Reels in Sushi Joints & Celebrities
80beats: Toothy Sea Monsters Need Sanctuary, Too

Image: flickr / avixyz

The Great Lakes are under threat from an Asian carp invasion that could wipe out fishing stocks, and with it, the lakes’ billion dollar fishery. On Friday, officials from the Army Corps of Engineers reported that genetic material from the carp had been found for the first time in a nearby river beyond an elaborate barrier system, which has cost millions of dollars and was meant to block their passage [The New York Times]. There is concern that if carp make it into Lake Michigan, they will gobble up the plankton that native fish feed on.

Officials also say that recreational boating may be affected–the carp can grow up to 4 feet long and weigh up to 100 pounds, and the massive fish will occasionally leap up and strike boaters. Since they were found to be moving up the Mississippi River in 2002, agencies have been trying everything they can think of to slow them down, including erecting the expensive electric barriers that cost around $9 million. The barriers work by sending low-voltage electric current through steel cables that are strung across the canal; this creates an electric field that’s uncomfortable for the fish and that’s supposed to prevent them from swimming across it.

(more…)

Toys, refrigerators, washing machines, socks—more and more products contain silver nanoparticles. It’s no wonder: These particles, which measure less 100 nanometers (smaller than a single HIV virus), can kill microbes on contact. But, researcher Darin Furgeson says, nanosilver can also escape into ecosystems and cause serious damage to fish embryos. Furgeson’s team published its results in the journal Small.

In one new experiment, Furgeson, a professor of pharmaceutical sciences, exposed zebrafish embryos to silver nanoparticles in a laboratory, and found that some died and others were left with dramatic mutations. “Some of the fish became extremely distorted, almost making a number nine or a comma instead of a linear fish,” he said [Scientific American]. Eyes, tails, and other body parts turned out malformed in the fish that survived.

Just how much nanosilver gets into the environment? A separate study from Environmental Science & Technology washed nine kinds of nanosilver-containing textiles, including some “anti-bacterial and anti-odor socks” that are already on the market. The researchers found that anywhere from less than 1 percent to as high as 45 percent of the silver came out in the first wash. Most of the silver was in the form of coarse particles of greater than 450 nanometers, suggesting that mechanical stress in the washing machine was responsible for most of the release [The New York Times], and that the nanoparticles might have aggregated to reach that size.

Those nanoparticles flushed out by a washing machine can end up in both fish habitats and drinking water supplies. Furgeson says his fish experiments could help show whether nanosilver is a health concern for humans, too. “Zebrafish have similar tissues and organs to us,” Furgeson said. “They don’t have lungs, but they do have a liver, kidneys and heart – though it is only two chambered – and they have a blood-brain barrier” [Scientific American].

Related Content:
80beats: Scientist Smackdown: Can Nanoparticles Damage Human DNA?
80beats: Golden Nanocages Could Deliver Cancer Drugs to Tumors
80beats: Nanoscale Origami: A Box—With Lock & Key—Made Entirely of DNA
80beats: Did Chinese Factory Workers Die From Inhaling Nanoparticles?

Image: Wiki Commons / Kristof vt

Atlantic bluefin tuna populations have declined so drastically that trade in the fish should be completely outlawed, says a new report. The population of the Atlantic tuna, a sushi staple, is now about 15 percent of the original stock size, says International Commission for the Conservation of Atlantic Tunas’ (ICCAT). The report has delighted conservation groups, who have criticized ICCAT’s regulation policies. The report was triggered by Monaco’s recent proposal to ban international trade in the Atlantic bluefin under the Convention on International Trade in Endangered Species (CITES) – a proposal that has gathered support from several other European countries [BBC News].

ICCAT has a history of setting quotas higher for the fish than scientists say is safe, while CITES seems to take a more proactive approach.Atlantic bluefin tuna are mainly caught from countries around the Mediterranean Sea, but most of the meat is consumed in Asia, particularly Japan. Japan has previously argued that commercial fish species should be controlled by bodies like ICCAT rather than CITES [BBC News]. In Japan, the fish are so highly prized that a single giant tuna can sell for more than $100,000 at the wholesale fish market. ICCAT will meet in 10 days to discuss the report.

Related Content:
80beats: Human Appetite for Sharks Pushes Many Toward Extinction
80beats: Are Fish Farms the Answer to World Hunger or a Blight on the Oceans?
80beats: Documentary on Endangered Bluefin Tuna Reels in Sushi Joints & Celebrities

Image: Wikimedia Commons

Snooty wine pairing rules, such as the edict that one must only drink white wine with fish, now have a little data behind them, according to a new study. Researchers found a correlation between the high iron content of red wine and a nasty, fishy aftertaste when the reds are sipped with seafood. In the experiment, tasters ate a bit of scallop, tasted some wine and evaluated the aftertaste on a scale of 1 to 4. The diners found the unpleasant aftertaste was more intense with wines that had a higher iron content, the researchers say [Los Angeles Times]. The researchers were able to block the aftertaste by adding a compound that masks the iron.

The iron content of a wine depends on the composition of the soil in which the grapes were grown, the dust on the berry, contamination during harvesting, transportation, and crushing, and the conditions during fermentation [Telegraph]. The new research, published in Journal of Agricultural and Food Chemistry, suggests that some low-iron red wines are OK to drink with fish. While red wines tend to have more iron than whites, it varies according to the type of grape, country of origin, and vintage.

But the iron is only half the story. The researchers report that they haven’t yet isolated the compound in the scallops that reacts with the wine, but they suspect it’s an unsaturated fatty acid, which could be breaking down rapidly and releasing the decaying fish smell when exposed to iron [ScienceNOW Daily News].

Related Content:
80beats: Fabulous Fizz: How Bubbles Make Champagne Burst With Flavor
80beats: Chemistry Experiment Produces the Ultimate Wine Taster
80beats: Tiny Tree Shrews Live on Alcohol, but Never Get Drunk

Image: flickr / yashima

Nissan is looking to schools of fish to learn about how to help people reduce car crashes and traffic jams. The car company developed tiny robots that move in fish-like groups of up to 7 without bumping into each other. Each uses a laser range-finder to measure the distance between obstacles. The data is constantly shared between peers via radio, allowing the group to travel as a “shoal” without bumping into each other. The technique allows the cars to travel side-by-side or quickly switch direction as a group [BBC News]. The robot is dubbed Eporo, which stands for Episode O (Zero) Robot, meaning zero episodes, or accidents, and zero emissions.

This is Nissan’s second attempt at designing a crash avoidance system based on animal behavior. Their last attempt was the BR23C robot, modeled after the anti-collision behavior of bumblebees (check out a video of the bee based bot here). The Eporo, however, imitates three rules of fish movement: avoiding crashes, traveling side by side, and keeping close to other members of the school [CNET]. Nissan plans to unveil the Eporo at the Ceatec conference in Tokyo on October 6. 

Related Content:
80beats: Robo-Fish Are Ready to Take to the Seas
80beats: To Win the Evolutionary Race, Robots Learn to Deceive
80beats: Scientists Glean Secrets of Flight From Birds, Bats, and Bugs

Image: Nissan

In a landmark concession that will likely lead to the largest dam-removal effort in U.S. history, an electrical utility company has agreed to destroy four dams on the Klamath River to help migrating salmon and steelhead. The dams won’t be decommissioned until 2020 and there are still regulatory hoops to jump through, but fishermen and environmentalists are delighted by the development. “We’re about to make changes to the Klamath Basin that will be observable from space,” said Craig Tucker of the Karuk tribe, which traditionally fished for salmon [Los Angeles Times].

The Klamath River, which winds through Southern Oregon and eventually reaches California’s Pacific coast, was once home to one of the most vibrant salmon runs in the West. But since the first dam was erected in 1908, the region has been host to a nasty battle over water rights, with wildlife and commercial fishers ultimately bearing the worst scars as regulators were forced to repeatedly close salmon fishing along 700 miles of the Oregon-California coast [Greenwire]. The removal of the dams’ will open 300 miles of river to the salmon.

Related Content:
80beats: Controversial Study Says Dams Aren’t Killing Off the Pacific Salmon
80beats: California’s Water Management Threatens Salmon With Extinction

Image: flickr / patrickmccully

Scientists have located a biological dimmer switch in a species of electric fish that uses electricity during everything from swimming to mating. The switch comes in handy when they don’t need to be electrified; during the day, the fish turn their current down to save energy for other activities, according to a new study in PLoS Biology. That means that the South American river fish, Sternopygus macrurus, is a natural practitioner of energy efficiency. It can reshape the charged-molecule channels in its electricity-producing cells to tone down its electrical signature within a matter of minutes [Wired.com].

Scientists found the dimmer switch in the membranes of cells called electrocytes within this electric organ. The switch takes the form of sodium channels that the fish can insert and remove from the electrocyte membranes. More sodium channels mean a stronger electric impulse [LiveScience]. Because the energy is expensive to produce for the fish, they do what the rest of us do when energy gets expensive–turn it off. The fish keep sodium channels on stand-by in the electric cells so they can switch the electricity back on in a moments notice if something spooks them.

Related Content:
80beats: Robo-Fish Are Ready to Take to the Seas
80beats: To Keep Predators Away, Snake Pretends Its Rear Is a Head
80beats: Lizard Swims Through Sand by Retracting Its Legs & Moving Like a Snake

Image: flickr / walknboston

The tiny island nation of Palau has taken a big step to protect the ocean’s endangered sharks, by designating all of its territorial waters a shark sanctuary within which all commercial shark fishing is prohibited. Palau’s president, Johnson Toriboing, announced the plan at a meeting of the UN General Assembly last Friday. Sharks are increasingly under threat as the demand for shark-fin soup—a delicacy in many Asian countries—has risen worldwide. “The need to save the ocean and save sharks far outweighs the need to enjoy bowls of soup,” Toriboing said [National Geographic News].

Palau consists of about 200 small islands in the Pacific Ocean to the east of the Philippines; its expansive marine territory spans 230,000 square miles, an area about the size of Texas. About 130 species of rare sharks either make their homes or pass through these waters, including hammerheads, leopard sharks, and reef sharks, as well as the related stingrays.

(more…)

Even European eels enjoy a trip to the Bahamas, for mating season of course. The eel travels thousands of miles to the Sargasso Sea, in the Atlantic Ocean near the Bahamas, just to get a little action. Scientists wanted to see what the little eels were up to on their trek, so they equipped a few with satellite tags and tracked their journey, which surfaced in Science this week. The tags allowed researchers to follow 22 eels for the first 1,300 kilometers of their trek from the coast of Ireland to mating grounds near the Bahamas. Understanding the details of the eels’ journey may help to protect this critically endangered species, a favorite of sushi eaters [Science News].

The tags recorded location, speed, depth and direction of the eels for 6 months, before popping off and floating to the ocean’s surface to beam their data back to the laboratory. The researchers found the eels swim too slowly to get to the Sargasso Sea by the April spawning period. The researchers suggest this means the eels may gain speed and travel efficiency by entering the ocean currents that begin west of Africa and continue as part of the subtropical gyre system that flows to the Caribbean [BBC News]. The data also show that the eels swim in shallow, warm water at night and dive to depths of 3,200 feet during the day swims. Since the eels do not feed on their trip, scientists think swimming in warm water boosts metabolism, while the cold water helps slow sexual development until they reach the Sargasso Sea.

Related Content:
80beats: Tiny Bird Backpacks Reveal the Secrets of Songbird Migration
80beats: Monarch Butterflies Navigate With Sun-Sensing Antennae
80beats: Blue Whales on the Move: Good News or Bad Sign?

Image: flickr / wwarby

Long gone are the days when a “robotic movement” meant something jerky, awkward, and stiff: The new robo-fish that have just been unveiled by engineers at the Massachusetts Institute of Technology swim through the water with sinuous grace. The flexible fish move naturally, as the motor in the middle initiates a wave that moves along the body and propels it forward. Real fish move in a similar fashion by contracting muscles on either side of their bodies [CNET]. The robo-fish are the descendants of Charlie the Robotuna, a large robot created at MIT in the 1990s that consisted of almost 3,000 parts. The new fish measure less than a foot long and use only 10 parts; researchers say the simple, durable fish are cheap to produce and hard to damage. To manufacture each robot, a single motor is placed in a fish-shaped mold before a liquid polymer is poured in and allowed to solidify. The continuous polymer casing prevents water from seeping in and damaging the motor, says Pablo Alvarado, an engineer who helped design the fish. “These materials are very resilient,” he said. “Water can’t do much to them and they can survive very high temperatures. Unless another fish eats them, they could go on and on” [Wired.com].

(more…)

A study that set out to determine the how many of the fish in our nation’s streams are contaminated with mercury came back with an ominous answer: quite possibly, all of them. Researchers from the U.S. Geological Survey sampled 34 species of fish at 291 stream sites across the country, and found mercury in every single fish they tested. “This study shows just how widespread mercury pollution has become in our air, watersheds, and many of our fish in freshwater streams,” U.S. Interior Secretary Ken Salazar said [Los Angeles Times].

A quarter of the fish had mercury levels that are considered unsafe for people who eat fish regularly, according to the Interior Department. The main source of mercury to most of the streams tested, according to the researchers, is emissions from coal-fired power plants. The mercury released from smokestacks rains down into waterways, where natural processes convert it into methylmercury — a form that allows the toxin to wind its way up the food chain into fish [AP]. But fish with high mercury levels were also found in Western areas that have been mined for gold or mercury.

Related Content:
80beats: Where to Put Thousands of Casks of Toxic Mercury? Not in My Backyard.
80beats: FDA Report: Fish Is Good for Brains Despite Mercury Risk
DISCOVER: Our Preferred Poison, mercury is everywhere
DISCOVER: Do You Really Want to Eat That Tuna?
DISCOVER: How to Tell If You’re Poisoning Yourself With Fish

Image: flickr / kasperbs

The world’s fisheries may be seriously depleted, but a comprehensive new study shows that all is not lost–and suggests that when humans really put the effort into turning the tide, fish stocks can be returned to good health. The researchers found that efforts introduced to halt overfishing in five of the 10 large marine ecosystems they examined were showing signs of success. A combination of measures – such as catch quotas, no-take zones, and selective fishing gear – had helped fish stocks recover [BBC News].

The new study sprang from another report from marine ecologist Boris Worm in 2006, in which he made an alarming prediction: if current trends continue, by 2048 overfishing will have destroyed most commercially important populations of saltwater fish. Ecologists applauded the work. But among fisheries management scientists, reactions ranged from skepticism to fury over what many called an alarmist report [The New York Times]. Eventually the two groups agreed to collaborate on a study that would bring both their perspectives to the table, and which would determine the best ways to revive and manage the ocean’s fish stocks.

(more…)

Many animals depend on stealth to catch prey, but a small tentacled water snake resorts to downright trickery. That’s what a Vanderbilt University scientist found when he analyzed the way the snake captures fish, according to a study published in the Proceedings of the National Academy of Sciences.

The snake, which is native to Southeast Asia, takes advantage of a well-known reflex that fish possess. The mechanism occurs when a fish’s ear senses changes in water pressure due to movement nearby, which is all it takes to initiate the fish’s escape response, called the C-start — one of the most well studied neural circuits in vertebrates. Two large nerve cells, known as Mauthner cells, run along either side of the fish’s body and detect water disturbances. The cell closest to the signal will fire action potentials that stimulate trunk muscles on the opposite side of the body while simultaneously inhibiting the muscles on the near side. As a result, the fish turns away from the disturbance and flees. This whole process takes less than a tenth of a second [The Scientist]. The reflex causes the fish’s body to form a “C” as it turns away from the source of the underwater vibration—but in this case, that leads the fish right into the snake’s jaws.

(more…)