The wild pink salmon of western Canada are in trouble: In the early 2000s, their numbers in some locations swiftly dropped by 90 percent or more. One explanation put forth for this steep population decline is that sea lice, parasites ubiquitous on farmed salmon, jumped to the wild variety of the fish. But this week in the Proceedings of the National Academy of Sciences, a new study casts doubt on that idea and says the sea lice are not to blame.
When Gary Marty of the University of California, Davis, and his colleagues looked at that aspect for the Broughton Archipelago of western Canada, they found that salmon survival was not lower in years when the juveniles passed by louse-infested farms. This, they say, suggests that something other than sea lice must be reducing survival rates. [New Scientist]
Marty’s team checked up on a decade worth of data dating back to before the 2002 crash, and found a few interesting things. First, they say, the predominance of the lice in wild populations appears to predict the number found in farms a little later, suggesting the parasites travel from wild salmon to farmed ones and not the other way around. Second, they argue, it does appear that a high number of lice in the farmed fish predicts higher than normal exposure for the juveniles of the wild variety, but that increased exposure can’t account for the huge population drop in the wild salmon.
Marine scientists have completed the first ever census of the myriad creatures living in the world’s deep blue seas, a monumental accomplishment that took 2,700 researchers 10 years to accomplish. While the scientists didn’t count every single fish head, they now know more than ever before about what kinds of life inhabit the oceans, what lives where, and the number of creatures that remain. They hope that this sound science will produce sound decisions on environmental policy and fishery management.
The Census of Marine Life was officially launched in 2000. After a decade of work, some of the most interesting findings are the delineations of the ocean’s unknowns. For example, the Census upped the estimate of the number of known marine species to nearly 250,000, but still couldn’t estimate the total number of species in the ocean. It might be millions, the report says, or tens or hundreds of millions, when all the ocean’s microbes are accounted for.
When an archer fish gets peckish and goes hunting for a juicy insect meal, it cruises toward the water’s surface with its ammunition packed in its mouth: As soon as it spots an insect above the surface, it fires out a jet of spit. This remarkable marksman has been known to bring down insects hanging from tree limbs as high as 3 feet above the water’s surface. And according to a study just published in the Proceedings of the National Academy of Sciences, it uses a visual processing technique that was previously thought to exist only in mammals.
The study found that fish pay attention to something called orientation saliency, which means that fish can more easily spot an object that is oriented differently from its background. The researchers first trained some archer fish to spit at the image of an insect projected on a LCD screen above their tanks, then presented images of objects that were either aligned with or perpendicular to a patterned background. They found that the fish spit far more accurately at objects that were not lined up with the background. (See video of a spitting fish in the lab below.)
Science: It’s best with stuffed fish and a wind tunnel.
When flying fish leap from the water and glide through the air, they appear as streamlined as any bird or insect. But how does one put that assumption to the test? Easy: Catch flying fish from the Sea of Japan (or East Sea, as South Korea calls it), kill them, stuff them, place them in a wind tunnel, and turn on the breeze.
Hyungmin Park and Haecheon Choi did just that. Their study of airflow around the fish, which is out in The Journal of Experimental Biology, concludes that flying fish glide as efficiently as some birds, and perhaps even more so than some flying insects.
In about a week and a half, officials at the Food and Drug Administration must complete their final deliberations over whether or not to approve a genetically modified salmon as the first GM animal in the world sold for human consumption.
It would seem they’re leaning toward “yes.”
Last Friday, while the country was preparing to go on vacation, the FDA released an analysis (pdf) of the transgenic salmon created by AquaBounty Technologies of Waltham, Massachusetts, declaring it safe to eat and safe for the environment.
The AquAdvantage Atlantic salmon contains a growth hormone gene from the Chinook salmon that is kept active all year round by a genetic on-switch from a different fish, the ocean pout. Normally, salmon produce growth hormone only in warm weather. So with the hormone produced year round, the AquAdvantage salmon grow faster [The New York Times].
“Faster” is an understatement. A normal Atlantic salmon requires about 30 months to grow large enough so that it can be sold at market. But a GM salmon with year-round growth hormone bulks up to market size in barely more than half that time—16 months or so.
Bluefin tuna–they’re so delicious, they’re on the brink of extinction. The human appetite for this majestic fish has spurred overfishing that has endangered the wild population, so researchers and aquaculture companies are trying to breed the fish in captivity. But so far bluefin tuna have proved very difficult to farm, since it’s impossible to replicate their natural reproductive cycle–researchers think the fish travel hundreds of miles to their traditional spawning grounds. The best results so far have come from an Australian company that is using hormone injections to get the big fish to breed.
Now researchers associated with a European project called Selfdott (an odd acronym for “self-sustained aquaculture and domestication of thunnus thynnus”) say they can successfully raise fish in captivity without using hormones. The New York Times reports that the first batch of fish, raised in floating cages, died after a matter of weeks or months, but researchers still think that with better food and parents more adjusted to captivity, the next group of fish will survive.
“If the results of this research can ultimately be commercialized, it can improve food supplies and contribute to economic growth and employment while also helping to ensure a sustainable management of bluefin tuna,” Máire Geoghegan-Quinn, the European Union’s commissioner for research, said this week. [New York Times]
Sure, the planet’s increasing carbon dioxide levels are making the oceans more acidic, but what does that really mean for sea life? We’ve already heard that the ocean’s changing chemistry is damaging corals and interfering with mussels, but that’s just the beginning. It turns out things could get seriously weird.
In a paper published this week in The Proceedings of the National Academy of Sciences, researchers led by Philip L. Munday of James Cook University have given us a concrete example: the increased CO2-levels make some fish purposely swim towards predators.
As part of his experiment, Munday used a Y-shaped maze to force baby clownfish to choose between two paths. One path reeked of rock cod, a natural predator; the other had no danger scents. Munday’s team compared the choices of fish raised in water of varying carbon dioxide concentrations, from today’s levels of 390 parts per million up to future expected levels of 850 ppm.
Coming soon: Salmon that grow to full size in half the time?
With all sorts of genetically modified crops on the market and in the grocery store in the United States, genetically modified animals have been the next step waiting to happen. The New York Times reports that salmon could be the first up: This year the Food and Drug Administration will weigh approval of a GM salmon created by the company AquaBounty, which could be the first GM animal eaten by Americans.
It is an Atlantic salmon that contains a growth hormone gene from a Chinook salmon as well as a genetic on-switch from the ocean pout, a distant relative of the salmon. Normally, salmon do not make growth hormone in cold weather. But the pout’s on-switch keeps production of the hormone going year round. The result is salmon that can grow to market size in 16 to 18 months instead of three years, though the company says the modified salmon will not end up any bigger than a conventional fish [The New York Times].
Your brain is hungry. That big gray calculating machine in your head is an energy hog that needs lots of calories—more than the diet of fruits and plants that our distant hominin ancestors probably ate could provide. It’s a mystery, then, just how human ancestors like Homo erectus—who were around when our craniums started to expand in a hurry—ate enough to start growing big brains. But buried in Kenya, a two-million-year-old hint has emerged: Those hominins started eating seafood way back then, archaeologists say.
Near a place called Lake Turkana, archaeologists David Braun found two intriguing groups of items: The bones of fish, turtles, and even crocodiles with the scars of stone tools still showing, and stone fragments that Braun says come from the simple tools these hominins used to carve up the marine animals. He and his colleagues report the find of our ancestors’ ancient feast in the Proceedings of the National Academy of Sciences.
Today, their leftovers—in the form of hundreds of bones and several thousand stone tools—are the earliest “definitive evidence” of hominins butchering and eating aquatic animals, which are rich in fatty acids essential for growing bigger brains [ScienceNOW].
The media-savvy eco-pirates of the Sea Shepherd Conservation Society have a new target in their sights: commercial fishing boats that illegally scoop endangered bluefin tuna out of the sea.
The Sea Shepherd activists have become famous for harassing Japanese whaling ships; a reality TV show about their exploits documented the many tricks the activists used to slow down the whalers, including shooting stink bombs onto their ships and attempting to disable their propellers. With their new project, dubbed Operation Blue Rage, the activists hope to bring the same level of attention to the fight to save endangered tuna.
Stocks of bluefin tuna have fallen by roughly 85% since the industrial fishing era began…. Yet despite quotas that are arguably too high to begin with, quotas are still being ignored in many places [Ecopolitology].