Fish decline linked to weather cycle in Atlantic

By Lucy Brake - 26 Jan 2011 10:7:0 GMT
Fish decline linked to weather cycle in Atlantic

The striped bass was once one of the success stories of conservation. Previously overfished, then serious catch limits were put in place and the population of striped bass was able to recover: fishermen where then once again able to fish for these large, trophy fish along the East Coast of America.

The problem right now is that catches of fish are down and the scientists are pointing to the weather as the primary culprit. Bob Wood, biologist with the National Oceanic and Atmospheric Administration (NOAA) says the weather, in particular the Atlantic Multidecadal Oscillation (or AMO), is actually having a major impact on the striped bass stocks.

The AMO is a cyclical weather pattern in the North Atlantic made up of ocean and wind currents that swap over about every 30 years. Wood and his fellow researcher, Ed Martino, believe the AMO weather pattern is responsible for the cycles in fish populations: "Circulation changes in a way that warms the entire basin and you can imagine if you warm the entire North Atlantic basin, you're changing the weather because the air and circulation patterns above the ocean are affected".

Martino is a fisheries scientist and he is of the opinion that when the AMO shift takes place then it has a major impact on the localised weather patterns all along the Atlantic coast of America: "You are talking about differences in temperature and precipitation, and therefore river flow or salinity, ultimately all affecting the base of the food chain”.  This is really all about the way that the localised climate has an impact on the microscopic plankton. Plankton refers to all the tiny animals and plants in the water that the juvenile striped bass feed on.

The research being undertaken by Wood and Martino and their team indicates that in the years following a warm phase of the cycle where there is more rain and more food, fish numbers increase. But as the AMO changes to the dryer cycle, less rain and less food, then in the years following the striped bass numbers will start to decline. Wood points to over 100 years of records that support this trend. "It hasn't been so good in say the last five years," Wood says. "And it just so happens this is also the time when the Atlantic Multidecadal Oscillation seems to be switching phase”.

The U.S. Environmental Protection Agency views this research as being really useful for fisheries management. So when they know the AMO is in a warm cycle the managers of striped bass fisheries will be able to increase catch limits and when the AMO is in a dry cycle, the catch limit would be decreased. However, if this latest research is correct then in the very near future tougher limits on catches of striped bass will be needed to help keep the population at a sustainable level.

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