( biological oceanographers on the natur...)Scripps scientists find potential for catastrophic shifts in Pacific ecosystems

"Classical fisheries management theory using fixed production functions (fixed growth rules) and fixed harvest targets is no longer supportable," says Sugihara. "The beguilingly simple statement that different sets of growth rules will apply in different physical environments, combined with a randomly fluctuating environment, gives support to a current trend in fisheries toward adaptive management strategies. Fisheries harvest targets need to be flexible and precautionary. This result strengthens the scientific basis for these polices."

The new study is believed to be the first direct test for nonlinearity in large-scale physical and biological data for the marine environment. The basic methods for testing for linear and nonlinear signatures were developed by Sugihara over years of studying a variety of complex systems (ecosystems, atmospheric systems, neurobiological systems, cardiac rhythms, market systems) and their dynamics and have been proven in small-scale ecological applications, medical applications, meteorological applications and in financial applications by investment banks.

"We have shown by analyzing this data with these methods that there is a limit as to what our understanding of the physical and biological interactions is going to be," say the researchers. "It appears we will never be able to explain these processes in a clean and simple way." Still, there is room for optimism. The authors believe that "with luck and work we may be able to make modestly accurate statistical forecasts over short time horizons as shown with certain reef fish (Science 1999)." The paper by the Scripps team helps to clarify the scientific basis of the next decade's challenge for fisheries and ecosystem management.