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Gray Whale Spotted in Israeli Waters; Pacific Squid in the Southwest Atlantic
06/16/2010
| Marilyn Sigman, Alaska SeaGrant/MAP
Tags: Climate Change, Squid, Gray Whale, Changing Species Distributions, Changing Ocean Current Patterns
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In early May, 2010, Israel's Marine Mammal Research and Assistance Centre photographed and positively identified a gray whale off the coast of Israel, near Herzliya Marina. Gray whales are thought to be extinct across the Atlantic Ocean, so the appearance of an individual within the Mediterranean Sea is a major surprise.The whale may have inadvertently travelled a huge distance from its natural habitat thousands of kilometers away in the Pacific Ocean. However, it raises the possibility that gray whales have returned to former haunts in the western hemisphere. More recently, deep sea fish species found in the North Pacific Ocean were caught in the southwest Atlantic.
A deep sea squid, a giant rattail grenadier, and a pelagic eelpout were discovered 15,000km from their usual home, which raised the possibility that deep sea currents can transport animals from one polar region to another. Details were published in the journal Deep Sea Research part I. "These findings were completely unexpected," says Dr. Alexander Arkhipkin of the Falkland Islands Fisheries Department, based in Stanley, on the Falkland Islands in the southwest Atlantic Ocean. Since 1987, the Falkland Islands Fisheries Department has performed surveys of fish caught by commercial and research fishing trawlers travelling above the Patagonian Shelf and slope around the islands.
All three species habitually live in the deep waters of the north Pacific, at depths greater than 600-1000m. That makes it extremely unlikely that the fish and squid could have become trapped in ballast water used by ships, and transported around the world. All three species live above the seafloor, and none of the three are known to habitually migrate, just as tuna and whales do. Far more likely is that each animal was transported thousands of kilometers by deepwater currents that flow south, across the equator, moving past South America underneath another northbound flow called the Humboldt Current.Finally, this flow mixes with another called the Upper Circumpolar Deep Water to pass through the Drake Passage, which water currents flow slowly, so it may take a few years for a long-lived fish, or even several generations of short-lived fish or squid to migrate the whole way.
Dr Arkhipkin says the catches may force scientists to reevaluate their ideas about the distribution and movements of deepwater species. Though there is no evidence to support the idea, Dr Arkhipkin speculated that climate change may be influencing the deepwater currents, facilitating the novel spread of such animals. Source: BBC News.
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