Young Salmon Born Knowing Migration Route
Chinook salmon hatch in freshwater and then travel to the ocean to feed later in life.
April 25, 2012 -
Whole Foods, the Texas-based natural foods supermarket, no longer carries fish considered to be unsustainable. The Whole Foods ban includes fish that is either overfished or caught in a harmful way, according to their website. The popular Atlantic Halibut made the list, though the company will still sell Atlantic cod that is caught by hook and line or gillnets. "Stewardship of the ocean is so important to our customers and to us," David Pilat, the global seafood buyer for Whole Foods told the New York Times. "We're not necessarily here to tell fishermen how to fish, but on a species like Atlantic cod, we are out there actively saying, 'For Whole Foods Market to buy your cod, the rating has to be favorable.'" Here's a look at the list of fish that the superstore no longer sells and why.
Octopus Whole Foods uses ratings set by the Blue Ocean Institute, a conservation group, and the Monterey Bay Aquarium in California. The ratings are based on factors including how abundant a species is, how quickly it reproduces and whether the catch method damages its habitat.
Imported Wild Shrimp "At Whole Foods Market, we've been saying that our mission is to sell only wild-caught fish that has been responsibly caught. For a few years now, we've used color-coded sustainability ratings, from green (best choice) to red (avoid), to help you make an informed choice. Now we're putting our mackerel where our mouth is: To support greater abundance in our oceans, we're no longer carrying red-rated wild-caught seafood!" the company wrote on its blog.
Tuna (from specific areas and catch methods rated "red") On their website, Whole Foods says that they stopped selling "species that were extremely depleted in the oceans, such as orange roughy, shark and bluefin tuna" years ago. The company uses the sustainability ratings of the Marine Stewardship Council (MSC).
Rockfish According to the Monterey Bay Aquarium, "In recent years, reduced fishing has allowed many rockfish populations to recover from low levels. Gear concerns remain, however -- trawl-caught rockfish should still be avoided."
Swordfish Some of the gear used to fish swordfish "accidentally catches sea turtles, seabirds and sharks," according to the Monterey Bay Aquarium.
Skate Wing Skates are in the overfished category. Most are also caught with bottom trawls, which result in high levels of accidental catch.
Sturgeon According to Monterey Bay Aquarium, "Sturgeon farmed in the U.S. is a good alternative to most wild sturgeon, whose populations have seriously declined due to overfishing for sturgeon eggs (caviar)."
Tautog Also known as black fish, Tautog are considered a "vulnerable" species. They are found close to shore on hard-bottom habitats, occasionally entering brackish water.
Trawl-Caught Atlantic Cod Fishermen often catch cod with bottom trawl, large nets that skim across the seafloor. Trawling, according to the Monterey Bay Aquarium, "damages marine habitats and produces bycatch."
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Turbot A cousin of Pacific halibut, turbot are a right-eyed flatfish -- as they develop, their left eye migrates across the top of the skull toward the other eye on the right side. Turbot are yellowish or grayish-brown on top and paler on their underside.
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Without any prior migration experience, juvenile Chinook salmon can find their way to ancestral feeding grounds by using the Earth's magnetic field and an inherited internal map, according to a new study.
Lots of migratory animals use the Earth's magnetic field to orient themselves during migrations. But in most known cases, young animals learn routes from more experienced individuals, and then internalize the magnetic fields associated with those routes for subsequent trips.
Until now, loggerhead sea turtles have been the only animals confirmed to know ancestral migration routes from the moment they hatch. But now, researchers based at Oregon State University have found that juvenile Chinook salmon -- which hatch in freshwater streams and then swim to the ocean to feed within the first year of their lives -- also inherit a sense of direction to their families' migration routes. [Quest for Survival: Incredible Animal Migrations]
The researchers tested the internal maps of hundreds of juvenile salmon by placing individuals in test tanks, letting the fish acclimate for about 10 minutes and then manipulating the magnetic field around the tank using coils with electric currents running through them.
The team found that a significant number of salmon oriented themselves toward the magnetic fields that exist in their oceanic feeding grounds.
"Everybody was pretty surprised that the fish already had that ability," study co-author Nathan Putman, a researcher at Oregon State University, told Live Science. "Before the fish even hit saltwater, they already have a sense of what they should be doing if and when they should find themselves in a certain magnetic field."
Since salmon and sea turtles are so far apart on the evolutionary tree, the new findings suggest that other migratory marine animals likely have this ability as well. Two distantly related species rarely share evolutionary traits that other closer relatives don't share as well, said Putman.
Whereas many migratory bird species have the chance to learn their migratory routes from more experienced birds, young Chinook salmon don't generally have this option, because adults abandon them soon after they hatch. The inheritance of a magnetic map is, therefore, more crucial to salmon's survival than to that of other species with more adult support early in life, Putman said.
The researchers are now trying to determine exactly how precise the salmon's internal GPS is -- whether the fish come within feet or miles of their feeding grounds.
"My guess is that they will have a very coarse resolution at this young age, but as they get older and do get experience with the magnetic field, that resolution will continue to get better until they are adults," Putman said.
The study findings are detailed today (Feb. 6) in the journal Current Biology.
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