Growth rate fluctuations of herring in the Celtic Sea: a history of life on the edge

Abstract

The most south-western herring populations in Europe occur in the Celtic Sea, south of Ireland. Biological sampling has been conducted since the 1920s and routinely since 1958. This study collated and analysed these long term data for the first time. Overall results were examined in the context of time series of environmental data and population scale indices of population status. Size at age was low in the 1920s and 1950s, but increased to a peak in the 1970s before declining strongly until recently. Condition factor over time declined, whilst growth rates were greater in the 1960s and 1970s than in the 1980s and 1990s. Further analyses suggest that the changes are influenced by environmental factors, especially the North Atlantic Oscillation sea surface temperature, and the abundance of Calanus copepods. The implications of this work, for the rational management of this stock, are discussed.