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.
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.
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.
Human beings are increasingly making their homes on the coasts of continents, but this demographic shift is taking a toll on a sensitive coastal ecosystem that is often overlooked: seagrass meadows. A new analysis of seagrass abundance around the world found that 27 percent of these meadows have disappeared since 1879, and the rate of loss is accelerating. The study’s authors write: “Seagrass loss rates are comparable to those reported for mangroves, coral reefs and tropical rainforests, and place seagrass meadows among the most threatened ecosystems on earth….. Our report of mounting seagrass losses reveals a major global environmental crisis in coastal ecosystems, for which seagrasses are sentinels of change” [Nature News].
Endangered species expert Susanne Livingstone notes that despite these losses seagrass rarely makes it into the public consciousness. “It’s probably because they’re not as sexy [as corals], they’re not as attractive,” she says. “They’re just as ecologically important if not more so” [Nature News]. Seagrass meadows provide grazing for a variety of marine animals, including the green turtle and the manatee-like dugong. The coastal areas also serve as nurseries for fish; both coral reefs and commercial fisheries would feel the impact if seagrass meadows vanish.
A tiny fish common in European streams may learn in a more sophisticated way than has ever been recorded among animals and which mimics human learning. In a study published in the journal Behavioral Ecology, scientists found that the nine-spined stickleback fish used the success and failures of their peers to gauge where they should seek food.
The fish were shown to display a type of learning known as “hill-climbing,” in which an entity continually looks for a better solution to a problem; in this case, one fish copied others that were more successful in finding food. Researchers caught 270 nine-spined sticklebacks in Leicester, England. The fish were organized into experimental groups. These fish groups then took turns as either free swimmers in a tank with worm-yielding feeders at the end, or as “learners” in a transparent, partitioned-off area of the specially designed tank. One of the two feeders released more worms than the other [Discovery News].
The first group of free-swimming fish quickly learned which feeder was full of worms, and were then put into the observers’ chamber. Next, researchers switched which feeder held the worms, and the fish in the observation tank watched the next fish group identify the new worm-filled feeder. After switching the two groups of fish again, the original group made a beeline for the feeder full of worms that their peers had fed from.
From pandas to polar bears, animals have served as icons for wildlife conservation. Now a new documentary called The End of the Line has helped the bluefin tuna, an endangered species, swim into the limelight by highlighting the overfishing common in fisheries today. Based on a book by journalist Charles Clover, the film has spurred some retailers to remove bluefin from their menus and stores and even moved some celebrities to pose naked with the fish to advocate conserving them.
A growing demand for bluefin tuna, commonly found in sushi and now as endangered as the giant panda, has not only decreased the fish’s population, but also increased the number of undersized fish that are harvested, preventing the fish from reaching maturity. “Bluefin tuna has become the poster boy for the overfishing campaign. It’s on the buffers – it’s really on the slide down now,” Clover says. “There are no large tuna anymore. There were bluefins of 250lb in Japanese fish markets when I went there four years ago – there are none now. A third of the catch is undersize” [BBC News].
The solution, experts say, doesn’t necessarily have to entail eschewing tuna altogether. Instead, consumers should stick to skipjack tuna, a more common variety, that has been caught using a method called pole-and-line, which avoids accidentally netting bluefish tuna and other sea life. Most commercial fishing operations that target skipjack use nets, Clover says, but “the skipjack run with all these other tuna species, like bigeye and bluefin. The skipjack are close to the surface and the bluefins swim further down, so there is often bluefin bycatch” [BBC News].
The fishing boats that relentlessly sweep the northern Atlantic Ocean looking for cod may be changing the genetics of the species, researchers say, in a case of “fisheries-induced evolution.” Commercial fishing techniques used to harvest the valuable fish are wiping out the cod that swim at shallower depths, which have a genetic variant that’s not seen in cod that stick to deeper water. If overfishing of cod continues, the research team believes the genetic variant will be lost all together. “Man the hunter has become a mechanised techno-beast,” the team writes. “Modern fisheries are uncontrolled experiments in evolution” [New Scientist].
Evolutionary biologist Einar Árnason and his colleagues studied the changing population of the cod fishery around Iceland; it’s one of the largest in the world, yielding roughly 200,000 metric tons a year. The stocks are in far better shape than the collapsed fisheries in the western Atlantic [ScienceNOW Daily News]. In the new study, published in the journal PLoS ONE, the researchers examined how the genotypes of Icelandic cod have changed between 1994 and 2003.
China’s recent economic boom has come at the cost of polluted landscapes and newly endangered species, and now a new study explains how another species has been left teetering on the brink of extinction. The endangered Chinese sturgeon live in the East China and Yellow seas and return to China’s Yangtze River to spawn. Construction of dams on the river is thought to have contributed to a decline in the species, and an artificial propagation effort has not resulted in recovery of the fish [AP]. But the new study shows that a chemical called triphenyltin (TPT), which is commonly used in paint, may be the true culprit behind the sturgeon’s decline.
The tin-containing organic compound TPT is extensively used in paints to prevent the fouling of ship hulls and fishing nets. It is also used in fungicide to treat crops in China. A derivative of TPT is also used to eliminate snails in paddy fields [Reuters]. In the study, published in the Proceedings of the National Academy of Sciences, researchers found that river water polluted with the chemical is producing sturgeon with misshapen skeletons and deformed eyes.
Chemicals that prevent your house, sofa, and clothes from bursting into flames are ending up in coastal waters all around the United States, and could be damaging the health of both sea creatures and the humans who consume those animals, according to a new study from the National Oceanic and Atmospheric Administration (NOAA). Says the NOAA’s John Dunnigan: “This is a wake-up call for Americans concerned about the health of our coastal waters and their personal health…. Scientific evidence strongly documents that these contaminants impact the food web and action is needed to reduce the threats posed to aquatic resources and human health” [The Oregonian].
Polybrominated Diphenyl Ethers (PBDEs) are a class of flame retardant chemicals that have been widely used in consumer products since the 1970s. The chemicals are credited with saving hundreds of lives each year from the spread of fire, federal scientists said…. But studies on animals have shown that flame retardants can cause thyroid hormone disruption and interfere with developing reproductive and nervous systems [Los Angeles Times].
How do hundreds of millions of fish decide to join ranks and take a swim together? That’s the question researcher Nicholas Makris and his colleagues set out to answer in the shallow waters of Georges Bank, about 60 miles off the coast of Massachusetts. It was already known that on autumn evenings herrings emerge from the deep waters where they safely spend their days, form a massive shoal, and venture into the shallows to spawn. The fish congregate en masse to find mates more easily and to protect against predators [New Scientist].
Now, watching that shoal form in real time with an advanced new acoustic technology, researchers have discovered that the shift from a disorganized scattering of fish to a highly synchronized shoal takes place in mere seconds when the fish reach a critical mass; the signal spreads rapidly through the ranks to form a shoal that can be 12 miles across. Says Makris: “It’s not gradual; it’s — BANG” [Science News].
The fish living in rivers around American cities are being medicated, like it or not. A broad new study of fish in five metropolitan areas has shown that fish are contaminated with a cocktail of prescription medications, including pharmaceuticals used to treat depression, bipolar disorder, allergies, high cholesterol, and high blood pressure. Researchers say this new form of pollution, a consequence of our medicated society, may have environmental or health consequences that aren’t yet understood.
Pharmaceuticals end up in drinking water—and in fish—when people take medications and residue passes through their bodies into the sewers. Conventional sewage and drinking water treatment filters out some substances, or at least reduces the concentrations [Chicago Tribune]. But pharmaceutical traces make it through the sewage processing and end up in river water. When fish take in the water through their gills, the chemicals accumulate in their livers and other tissue.
A new United Nations report has sparked outrage with its suggestion that fish farming should be dramatically increased to keep pace with growing fish consumption. Although the U.N. report presents aquaculture as a way to take pressure off wild fish stocks, conservationists say that fish farms indirectly snatch the food from many wild predator fish, marine mammals, and birds.
Environmental groups say the report appeared to ignore the huge environmental problems posed by fish farms: particularly the need to “hoover up” vast quantities of smaller fish like blue whiting, anchovies, sardines and sand eels, and more recently even krill, to feed the farmed fish [The Guardian]. Critics also worry that water-borne antibiotics and hormones used in fish farms are polluting the ocean, and say that farmed fish are more likely to catch infectious diseases, which escapees can transmit to wild schools.
In a shale deposit in Kansas, researchers unearthed the intact skull of a prehistoric fish with a surprise inside: the oldest brain ever discovered. The fossilized brain dates from 300 million years ago, and was found in the skull of a fish called an iniopterygian, an relative of sharks and another latter-day species called the ratfish. Iniopterygians were once commonplace in the world’s oceans, living in shallow and muddy marine waters. They measured 50 centimetres (20 inches) at most [AFP].
Researchers were surprised and thrilled by the unexpected discovery. Other soft tissue fossils, such as muscles and kidneys, have been found that date back longer than 350 million years ago, but because the brain is delicate and consists mostly of water, it’s much less likely to be preserved in fossil form, says study co-author John Maisey…. In the fossilization process, the brain itself was replaced with hard minerals, which preserved the shape of the original organ, and the rest of the cavity was filled with sediment, Maisey says. [Scientific American].
A bizarre fish discovered off the coast of an Indonesian island has officially been declared a new species, and given a name that researchers say celebrates its oddity: Histiophryne psychedelica. The creature, a type of frogfish, has beige and pink stripes swirling away from its eyes, and has leg-like fins on both sides of its body. But researchers writing in the journal Copeia say the psychedelic fish uses those fins in a form of locomotion never before seen in fish.
When the fish was first spotted by scuba divers off the coast of Ambon island last year, the divers described it moving away from them in a series of short hops, its pelvic fins pushing it off the sea bed with each bounce. “The overall impression” says the Copeia research paper, was of “an inflated rubber ball bouncing along the bottom” [BBC News].
Prehistoric fish had sexual reproduction figured out 380 million years ago, a new fossil study has confirmed. Researchers examined the fossil of one species of armored placoderm fish and realized that the fossil showed a 2-inch-long embryo within the fish’s body cavity, indicating internal fertilization, or sex as we know it. Palaeontologist Zerina Johanson says: “We expected that these early fishes would show a more primitive type of reproduction, where sperm and eggs combine in the water and embryos develop outside the fish. This discovery is incredibly important because evidence of reproductive biology is extremely rare in the fossil record” [Telegraph].
Researchers originally thought the tiny bones within the fossil were the remains of the fish’s final meal, but they decided to reexamine the 380-million-year-old fossil after discovering embryos in the fossilized remains of another species of ancient fish last year. A closer look revealed that the placoderm also had a bun in the oven, says lead researcher John Long. “We could see that the new specimens had the same bone structure as the previous embryos, were the same species as the adult, they did not have any broken or stomach-etched features (from digestive acids or from being chomped) and that they were at the same stage of growth as the previous embryos,” Long wrote in an email. “All of these facts proved they were embryos, not prey items” [LiveScience].
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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]. 
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, 
Human beings are increasingly making their homes on the coasts of continents, but this demographic shift is taking a toll on a sensitive coastal 
A tiny 
From pandas to polar bears, animals have served as icons for wildlife conservation. Now a new documentary called 
The fishing boats that relentlessly sweep the northern Atlantic Ocean looking for cod may be changing the genetics of the species, researchers say, in a case of “fisheries-induced 
China’s recent economic boom has come at the cost of 
Chemicals that prevent your house, sofa, and clothes from bursting into flames are ending up in coastal waters all around the United States, and could be damaging the health of both sea creatures and the humans who consume those animals, according to a 
How do hundreds of millions of 
The 
A new 
In a shale deposit in Kansas, researchers unearthed the intact skull of a prehistoric 
A bizarre 
Prehistoric fish had 
