This document presents the results of a study undertaken under contract to FAO by Professor Leonid B. Klyashtorin of the Federal Institute for Fisheries and Oceanography, Moscow, Russian Federation (e-mail: [email protected]) . The study was inspired by discussions with FAO staff following a seminar given by Professor Klyashtorin in Rome in which he presented the results of previous work. Several people contributed to improvement of the document in various ways, including Dr Gary D. Sharp of the Center for Climate/Ocean Resources Study, Monterey, California, USA and Dr Paul Medley and Dr Gudrun Gaudian of Alne, Yorkshire, UK.
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The main objective of the 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.
Populations of the most commercially important Atlantic and Pacific fish species - Atlantic and Pacific herring, Atlantic cod, European, South African, Peruvian, Japanese and Californian sardine, South African and Peruvian anchovy, Pacific salmon, Alaska pollock, Chilean jack mackerel and some others - undergo long-term simultaneous oscillations. Total catch of these species accounts for about 50% of total fish harvest over Atlantic and Pacific.
It was found that the dynamics of global air surface temperature anomaly (dT), although in correlation with the long-term dynamics of marine fish production, is of poor predictive significance because of high inter-annual variability and a long-term trend. The Atmospheric Circulation Index (ACI), characterizing the dominant direction of air mass transport, is less variable and in closer correlation with the long-term fluctuations of the main commercial stocks (r = 0.70-0.90).
Spectral analysis of the time series of dT, ACI and Length Of Day (LOD) estimated from direct observations (110-150 years) showed a clear 55-65 year periodicity. Spectral analysis of the reconstructed time series of the air surface temperatures for the last 1500 years suggested the similar (55-60 year) periodicity. Analysis of 1600 years long reconstructed time series of sardine and anchovy biomass in Californian upwelling also revealed a regular 50-70 years fluctuation. Spectral analysis of the catch statistics of main commercial species for the last 50-100 years also showed cyclical fluctuations of about 55-years.
These relationships were 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 ahead. According to model calculations, the 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 then decrease. During the same period, the total catch of Japanese, Peruvian, Californian and European sardine, Pacific salmon, Alaska pollock and Chilean jack mackerel is predicted to decrease by about four million tons, and then increase. In the next 15 years, total catch of main commercial species in the North Pacific is predicted to decline by 1.5 -2 million tons, while in the North Atlantic it is predicted to increase by about 1.7 -2 million tons. The probable scenario of climate and biota changes for next 50-60 years is considered.
Key words: Global climate change, Stock fluctuations, Climate-production cycles, Pacific, Atlantic.