Fishing throws targeted species off balance, Scripps study shows

“In the extreme case, the danger of such unstable dynamics for certain populations for management is that harvest targets may lag the population, potentially making things worse,” said Sugihara. “A high harvest target may be set after an especially abundant period when the population may be poised to decline on it’s own. Likewise future abundant periods may represent missed opportunities, despite current low abundances. As senior officials of the Canadian Department of Fisheries and Oceans have said, ‘we are often a year behind in our stock projections.’”

Sugihara cautioned that nonlinearity is not unique to fished species. Nonequilibrium overshooting and undershooting occurs in unexploited stocks, but to a lower extent. Therefore, classical single-species population models that require equilibrium are unlikely to be very successful in stock forecasts, except perhaps in the very short term.

"Other methods that do not rely on these assumptions may be more promising," suggests Christian Anderson, paper co-author.

In addition to Sugihara and Anderson, the study included Scripps Oceanography alumnus Chih-hao Hsieh (now a professor at National Taiwan University); Stuart Sandin of Scripps; Roger Hewitt of the National Marine Fisheries Service, Southwest Fisheries Science Center; Anne Hollowed of the National Marine Fisheries Service, Alaska Fisheries Science Center; Sir John Beddington of Imperial College London (current Chief Science Advisor to the United Kingdom) and Lord Robert May of Oxford (a former Chief Scientific Advisor to the UK).

The research was supported by NOAA Fisheries and the Environment program, The MacQuown Chair of Natural History, The Deutsche Bank – Jameson Complexity Studies Fund, the Sugihara Family Trust and the Kyoto University grant for Biodiversity Research of the 21st Century.

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