Mechanisms governing fluctuations in pelagic fish populations

Abstract

A comprehensive and systematic review of 10 years' study on global fluctuations of clupeoid populations is presented and earlier ideas further developed. Historically, sardine and herring have undergone fluctuations of very large amplitude over long periods in a cyclic manner. Such a fluctuation, called Subtype IB, could not have evolved in any other than a marine environment. Sardine and herring have shown concomitant cycles of variation in biomass, but the two cycles are completely out of phase with each other. Sardine dominate the temperate pelagic fish community and changes in its abundance are responsible for structural changes of the community.