From: Science Daily
Published May 6, 2010 08:52 AM

Currents Influence Fish Stocks: More Cod in the Barents Sea

Back in the 1920s and 1930s, the Barents Sea was teeming with cod. That was before its waters substantially cooled off in the decades to follow. Now, with ocean temperatures higher once again, fishermen are seeing more fish.

The entire North Atlantic warmed up during the 1920s and 1930s. More fish appeared not only in the Barents Sea but also off Iceland and Greenland. This warm period reached its peak at the end of the thirties and lasted until roughly 1960, when the waters began turning colder again -- and fisheries resources declined once more.

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In recent years, the North Atlantic has shown signs of a new period of warming.

Warm waters then and now

Ken Drinkwater is a senior research scientist at both the Institute of Marine Research and the Bjerknes Centre for Climate Research, located in Bergen. He and his colleagues have been studying the causes of this latest warming trend -- and are finding many answers by poring through the literature describing conditions 80-90 years ago.

Dr Drinkwater rejects the common explanation that the Barents Sea is getting warmer because the atmosphere in the polar regions has warmed.

"This warming is primarily due to currents -- a greater amount of warm Atlantic water is flowing into the North Atlantic and up to the Barents Sea," asserts Dr Drinkwater.

That is what happened in the first half of the 20th century. Although there were large year-to-year temperature fluctuations then, the North Atlantic on the whole remained more temperate than normal until well into the 1960s.

"Many people recorded what they observed taking place in the ocean nearly 90 years ago. If we can determine what occurred during that warming period," believes Dr Drinkwater, "we will better understand what is going on today, plus we'll have more reliable input as to what we can expect in the future."

More and larger fish farther north

The warm period between the world wars led to some major changes in the ecosystem. In the Barents Sea and off Iceland and Greenland, cod catches reached record highs.

"In the 1920s and 1930s, the Arcto-Norwegian cod stock moved north. Fishing of cod was organised around Bjørnøya (Bear Island in the Svalbard archipelago) and more cod were being caught in Russian waters as well. The fishermen were catching cod that were about 50 per cent larger than in the previous decades."

Article continues: http://www.sciencedaily.com/releases/2010/05/100505092525.htm

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