Climate change and long-term fluctuations of commercial catches: the possibility of forecasting.

The main objective of this study was to develop a predictive model based on the observable correlation between well-known climate indices and fish production, and forecast the dynamics of the main commercial fish stocks for 5–15 years ahead. Spectral analysis of the time series of the global air surface temperature anomaly (dT), the Atmospheric Circulation Index (ACI), and Length Of Day (LOD) estimated from direct observations (110-150 years) showed a clear 55-65 year periodicity. Spectral an alysis also showed similar periodicity for a reconstructed time series of the air surface temperatures for the last 1500 years, a 1600 years long reconstructed time series of sardine and anchovy biomass in Californian upwelling areas, and catch statistics for the main commercial species during the last 50-100 years. These relationships are used as a basis for a stochastic model intended to forecast the long-term fluctuations of catches of the 12 major commercial species for up to 30 years ahea d. According to model calculations, total catch of Atlantic and Pacific herring, Atlantic cod, South African sardine, and Peruvian and Japanese anchovy for the period 2000–2015 will increase by approximately two million tons, and will then decrease. During the same period, total catch of Japanese, Peruvian, Californian and European sardine, Pacific salmon, Alaska pollock and Chilean jack mackerel is predicted to decrease by about 4 million tons, and then increase. The probable scenario of climat e and biota changes for next 50-60 years is considered.