Analysing the Effect of Age Structure on Stock–Recruitment Relationships in Herring (Clupea harengus)

Abstract

A Leslie matrix model, fit by multivariate time series analysis methods, of the southwest Nova Scotia herring (Clupea harengus) stock indicates that there is feedback from mature stock abundance to recruitment. Median smoothing suggests dome-shaped nonlinearity in this stock–recruitment relationship. Evidence for compensatory density dependence appears most strongly in the relationships of abundances of individual mature age groups and total recruitment. We suggest that this arises from the separation in space and time of spawners based on their size or age. This results in the production of distinct larval cohorts. These cohorts and the spawners which produce them are the units relevant for the examination of density-dependent processes, rather than the total numbers of spawners and recruits.