Monday, January 12, 2009

"Why Storms are Good News for Fishermen"

I always knew that weather played a role in how many fish I caught on a given day. I'm a fair weather fisher, so if the weather is bad, I stay at home! But, for those more dedicated fishermen and fisherwomen (sidenote: are women fisherMEN as well?) and for those who fish for a living, it turns out that the weather plays a pretty important role in a given fishing harvest.

According to an article in the New Scientist, individual storms or particularly cold winters can lead to bumper fish harvests years later:

In many cases [...] it comes down to the survival of the young. "It's all about making it through that first summer," says Nicholas Bond of the University of Washington in Seattle

Take the walleye pollock in the Bering Sea off Alaska, the basis of the largest single fishery in the world. [...] When Bond looked at the years in which high numbers of young pollocks survived, he found they were characterised by summer storms.

Storms matter because they bring up deep water rich in the nutrients essential for the growth of phytoplankton. "These events essentially fertilise the oceans," says Bond. During calm summers, phytoplankton growth slows early as the nutrients brought up by winter storms are used up. Summer storms refresh the surface waters, allowing phytoplankton to continue thriving - and young pollock to grow fat.

While predicting individual storms is not possible, says Bond, predicting their effects is. Three years after a stormy summer, when pollock that hatched in the good year become large enough to be caught, catches will rise. Recent falls in pollock numbers could be partly due to a series of calm, warm summers, he says, although 2006 was a good year for young pollock."

The case of the pollock mentioned above is just one example of harvest variability that is shown with changing weather conditions. Also mentioned in this article are salmon, crab, cod, tuna, and anchovies. Having climatic insight into a given fishing season's potential yield, 3 years in advance, could help to reverse the effects of the mismanagement of our fisheries here on the Pacific North Coast.

With many other fisheries teetering on the brink, these new insights could prove vital. If we can predict how fish numbers will vary naturally months or even years in advance, managers can reduce quotas before stocks are decimated, or increase them when conditions are favourable.

To read more about how different marine species are impacted by a change in climate, visit the full article in issue 2689 of the New Scientist.

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