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.
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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.
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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].
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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].
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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.
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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.
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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].
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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].
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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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The Arctic’s ice may be melting, but a vote by a federal fishing council makes it likely that fishing trawlers won’t be moving in to look for rich harvests in the newly accessible Arctic waters. In a preemptive move, the council voted to ban commercial fishing in almost 200,000 square nautical miles of the Chukchi and Beaufort seas along Alaska’s northern coast. These areas are not currently fished, but sea ice melt and the northward migration of certain fish species, such as salmon, raises the possibility that they would be in the not too distant future [Scientific American]. If the U.S. commerce secretary approves the proposal, the ban will remain in place until scientific studies can determine whether fishing can be conducted sustainably in the Arctic.
Says Jim Ayers, of the conservation group Oceana: “Global climate change is making everyone think differently up here and making them understand that precautionary approaches are best.” … The unanimous vote was unusual in that it was largely supported by industry and conservation groups alike and because it was the first time the United States had acted to close a fishery as a result of climate change instead of in reaction to overfishing [The New York Times].
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Ocean acidification, the second part of the one-two punch packed by global warming, has been shown to disorient young clown fish and prevent them from finding their way to their natural habitats. A new study found that dropping the pH of seawater interfered with the fish’s ability to sniff out environmental cues. Most research on the environmental impacts of acidification has focused on the vulnerability of shellfish, corals and crustaceans, whose shells are weakened and dissolved by acidic waters. But the latest findings show that fish may also be directly and profoundly affected [Wired News].
A little like the animated movie-star clown fish, Nemo’s real-life counterparts go out to sea upon hatching and some 12 days later must find their way back to a reef to settle down in an anemone home [Science News]. Researchers believe that the fish find their way by following odors in the water. In the new study, published in the Proceedings of the National Academy of Sciences [subscription required], researchers raised clown fish in tanks filled with water of varying pH, and then tested their ability to follow scents.
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Three pods of killer whales in the Pacific Northwest have now earned the unfortunate title of being the most contaminated wildlife on Earth, according to a new study. These killer whales, known as southern residents, live in the coastal waters near the U.S.-Canadian border and survive almost exclusively on contaminated Chinook salmon. The salmon contain high levels of polychlorinated biphenols (PCBs) and other industrial chemicals, which accumulate in even higher levels in the killer whales. Researcher Peter Ross says whales are particularly sensitive because they eat massive amounts of fish over a long life – killer whales can live for 80 or 90 years – creating a massive buildup of toxins. That means the whales, particularly the southern resident population, have become some of the most contaminated marine mammals in the world [AP].
Researchers estimate that the southern resident killer whales carry 6.6 times more PCBs than a different group of whales just 200 miles to the north, known as the northern residents. They found that the Chinook salmon in the southern waters, including Puget Sound near Washington state, not only had the highest concentrations of contaminants but also the least amount of body fat. This means the southern residents are suffering a “double whammy” because they are forced to eat extra helpings of heavily contaminated salmon. Ross and his colleagues discovered that 97 percent to 99 percent of contaminants in the Chinook eaten by these whales originated from the salmon’s time at sea, in the near-shore waters of the Pacific. Only a small amount came from the time the salmon spent in rivers, although many of the rivers are contaminated, too, Ross said. “Salmon are telling us something about what is happening in the Pacific Ocean,” Ross said. “They are going out to sea and by the time they come back, they have accumulated contaminants over their entire time in the Pacific Ocean” [Scientific American].
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The trick to controlling invasive blood-sucking sea lampreys—sometimes known as vampire fish—may be a love pheromone, according to a new study. Researchers have designed a synthetic version of the male lamprey pheromone that ovulating female lampreys find irresistible, and could be used to lure them into traps. This would be the first instance of using pheromones to control non-insect pests. “There’s been extensive study of pheromones in animals and even in humans,” said lead researcher Weiming Li… “But most researchers have presumed that as animals get more complex, their behaviour is regulated in a more complex way, not by just one pheromone,” [BBC News].
When Li’s team placed traps laced with the synthetic pheromone in a stream, female lampreys swam eagerly towards the trap. Only a whiff of the pheromone was needed to attract females from hundreds of meters away, the researchers report in the Proceedings of the National Academy of Sciences. “The pheromone is expensive to synthesize… But only a very small amount is needed for it to work successfully. It’s very potent. Only a few hundred grams, less than a pound, would be used each year” [LiveScience] said Li, who discovered the natural lamprey pheromone in 2002. Currently, lampreys are controlled mainly by adding TFN, a compound that kills the larval stage, to freshwater streams where lampreys spawn. But there are environmental concerns about adding the chemical to streams, as well as the possibility that lampreys could develop resistance to TFN [LiveScience].
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Contrary to conventional wisdom, fish in the Nile delta are thriving in waters polluted with fertilizers and sewage, according to a new study. While nitrogen-rich runoff usually causes excessive growths of algae and plankton that suffocate other marine life, the Nile delta is different because it has suffered from a lack of autotrophs (that fish feed on) ever since the Aswan Dam was built in the 1960s. Researchers found that more than 60 percent of the current fishery production in the region can be attributed to human-generated runoff. “This is really a story about how people unintentionally impact ecosystems,” explained co-author Autumn Oczkowski [BBC News].
The building of the Aswan Dam on the Nile blocked off much of the fertile floodwater that drains into the Mediterranean Sea, which in turn produced a sharp fall in the number of fish being landed by Egypt’s fishermen. “But in the late 1980s, the coastal fishery began to exhibit a surprising recovery,” the researchers observed. “Today, landings are more than three times the pre-dam level” [BBC News]. The increase in fish production coincided with the rise in fertilizer use along the Mediterranean coast. To quantify the effect, researchers collected more than 600 fish from four regions contaminated by runoff and two regions that were not. In regions affected by runoff, the fish contained nitrogen isotopes that could be traced to anthropogenic sources of nitrogen, according to the study published in the Proceedings of the National Academy of Sciences.
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Two-headed fish are turning up in Australia’s Noosa River, and experts believe it’s due to something in the water. Millions of fish larvae have been found with two heads (that means one more eye than Blinky) and none of them survive to adulthood. Aquatic animal specialist Matt Lando puts the blame on noxious chemicals wafted from a nearby macadamia nut farm. He said, “When we used the water on-site or have taken bass from the Noosa River those fish appear to have been contaminated and they give rise to deformed or convulsing larvae… I have been working in aquaculture for 10 years and this is the first time I have ever seen anything like it” [AFP].
Last October, Lando sent a report to the Department of Primary Industries and Fisheries in which he identified the pesticide endosulfan and the fungicide carbendazim, both used on the neighboring macadamia nut plantation, as the likely culprits. “The timing between the mist spraying and the affected larvae fits hand in glove,” he said. Dr Landos’s report also found that chickens, sheep and horses raised at the Sunland Fish Hatchery at Boreen Point were recording abnormally high levels of foetal deaths and birth defects [The Sydney Morning Herald]. Both chemicals are currently legal in Australia. Carbendazim was voluntarily withdrawn from the U.S. market in 2001 by the chemical company Dupont. Endosulfan is already banned in 55 countries and New Zealand will become the 56th starting this Friday.
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