Changes in ocean conditions in Sargasso Sea potential cause for decline in e...(ic oceans are catadromous which means th...)

Date:3/6/2008

ic oceans are catadromous, which means they spend most of their lives in rivers, lakes and estuaries but migrate to the ocean to spawn. Both European and American eels spawn in the open ocean in the Sargasso Sea, in an area between the Bahamas and Bermuda, where distinct temperature fronts are present in the winter and spring that form a northern boundary of the spawning area, believed to be used by eels to locate mates and favor survival of their young.

After hatching, their transparent leaf-like larvae, known as leptocephali, remain in surface waters for up to a year and drift towards the Gulf Stream, which transports the European eels home to coastal waters in Europe. Along with the Gulf Stream, the Antilles Current and other westward-flowing circulation patterns in the North Atlantic send American eel larvae back towards the coast of the eastern US, where they migrate into estuaries like Chesapeake Bay.

Once back in coastal waters, the two to three-inch larvae transform into typical eel-shaped transparent juveniles, or glass eels, named for their appearance. They gather in estuaries and wait for the river to warm before swimming upstream into freshwater, where they change color and acquire green and brown pigments to become known as yellow eels. They can spend up to 20 years living in the rivers and generally reach lengths of 30 inches before they return to the ocean. But before they go back to the Sargasso Sea, they undergo another physical change and take on a silvery color to become silver eels.

Changing ocean conditions in the Sargasso Sea caused by the NAO could be affecting the recruitment and survival of European eels, Friedland says. Our findings provide evidence of linkages between declines in recruitment and specific environmental changes within the spawning and early larval development areas of the Sargasso Sea. The Japanese eel population in the North Pacific is facing similar environmental pressures linked to El Nino con
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Contact: Shelley Dawicki shelley.dawicki@noaa.gov 508-495-2378 NOAA National Marine Fisheries Service Source:Eurekalert

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