Sockeye salmon put on a lot of miles during their short life
. From the freshwater riverbeds where they hatch and spend their first couple years, juvenile salmon travel some 4,000 miles to the ocean where they fatten up for two years before turning around and retracing their steps.
But salmon can’t leave actual footprints, nor do they have the luxury of dropping waterproof bread crumbs so they can find their way back home. Scientists have long suspected that these big fish instead use the Earth’s magnetism to orient their inner compass. A recent study of 56 years’ worth of migration data presents pretty convincing evidence for this geomagnetic hypothesis and how it works.
A snow crab
If you’ve ever read up on the environmental impact of your eating habits, you know that eating fish can be a dicey prospect. Having been overfished for decades, many wild fish populations are on the brink of disappearing.
A new report from NOAA shows that one attempt to deal with this problem of severely depleted fisheries, the Magnuson-Stevens Reauthorization Act of 2006, seems to be helping, at least a little bit. The act states that each year, NOAA must give status updates on all fish populations within 200 miles of the US Coast. If the fisheries are hurting, fishermen must stop catching those fish until their numbers recover. Over the last 11 years, 27 previously precarious fish populations have been announced recovered; this year, the six lucky winners were the haddock in the Gulf of Maine, the Chinook salmon along the coast of Northern California, the snow crab of the Bering Sea, the summer flounder on the mid-Atlantic coast, the coho salmon on the coast of Washington, and the widow rockfish in the Pacific.
Overall, NOAA takes these recoveries as a sign that the law is doing its job; according to a metric called the fish stock sustainability index (FSSI), things have been steadily improving for US fish stocks since 2000. But it’s not necessarily a sign to order snow crab tonight. To be declared recovered, a Pew Environmental Group employee told the NYT’s Green Blog, a fish population only has to reach 40% of the numbers it had historically. That seems pretty far from true recovery.
Image courtesy of nelgdev / flickr
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.
An FDA advisory panel has decided what it thinks about genetically modified salmon, and its decision is to not make a decision. The committee says it doesn’t have enough data to fully support approving the biotech salmon, which would make it the first such animal in the country.
“We are missing data,” said panel member James McKean, a professor at Iowa State University. He said that “leaves a cloud” over the FDA staff’s analysis. [Wall Street Journal]
But some other panel members agreed with the FDA’s position that the fish was fine.
“In conclusion, all of the data and information we reviewed … really drive us to the conclusion that AquAdvantage salmon is Atlantic salmon, and food from AquAdvantage salmon is as safe as food from other Atlantic salmon,” said Kathleen Jones of the FDA’s Center for Veterinary Medicine. [ABC News]
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.
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].
It’s a question that has fascinated scientists for decades: When sea turtles and salmon decides to give up the freedom of the open ocean and head back to their birthplaces to breed, how do they find their way back? Some species of sea turtle migrate thousands of miles across entire oceans back to their birthplaces after leaving more than 10 years earlier. And after hatching in rivers, salmon travel hundreds of miles out to sea before returning home to spawn years later [Press Association]. Now one researcher thinks he has the answer. Marine biologist Kenneth Lohmann believes that these marine animals can detect the distinctive magnetic fields of different spots and use them to navigate.
“What we’re proposing is the sea turtles and salmon, when they begin life, basically learn or imprint on the magnetic field that marks their home area,” he said. “They retain this information. And years later, when it is time for them to return, they are able to exploit this information in navigating back to their home area” [National Geographic News]. Lohman says this doesn’t contradict the existing theory that when salmon reach coastal waters, chemical scents guide them upriver to the particular stream where they were born; those olfactory cues probably have a limited range, he says, and couldn’t extend thousands of miles into the ocean to guide the salmon all the way home.
In a new study that’s already generating controversy, researchers tracked more than 1,000 young Pacific salmon on their first journey to the sea, and found that those battling dams on the Columbia River fared no worse than the young fish with an easier path to the sea on Canada’s free-flowing Fraser River. The findings seem to contradict many previous studies about dams: Conservationists have blamed these obstacles for a large share of the shrinking salmon populations in the Pacific Northwest, and engineers have spent billions trying to make the dams less damaging to salmon [Science News].
The study used implanted transmitters to follow the juvenile salmon, called smolts, on their trips downriver, and found that only about 25 percent of smolts in both the Columbia and the Fraser survived the voyage and made it to the ocean. But environmentalists and several salmon biologists pounced on the study, suggesting that industry funding might have biased the results. These critics question the value of comparing the two rivers and say that the study doesn’t even address what many think is the dams’ biggest effect: stressed smolts dying after they reach the ocean [Nature News].