The influence of pre-recruitment growth on subsequent growth and age at first spawning in Atlantic herring (Clupea harengus L.)

Calculation of the spawning stock biomass for fisheries management requires information on the numbers or proportions of fish in each age- or length-group that are mature each year. This study was conducted to determine the relationship between growth and age of first reproduction in herring stocks around Ireland. Measurements of otolith size at the onset of the first annulus (O1) were used to compare growth during the first year of life between 1-, 2-, and 3-group spawning herring collected from spawning grounds in the Celtic Sea over a period of 3 years. The 1-group spawning fish had significantly greater mean O1 measurements, and hence showed faster growth on average during the first year of life than 2- or 3-group spawning fish. Fish that exhibited slow growth during the first year were absent from the adult spawning population at age 1, but occurred at similar levels in the samples of 2- and 3-group spawning fish. Regression of O1 radius on fish length at capture showed that growth during the first year of life had a small but significant effect on subsequent growth up to age 3. The relationship between pre-recruitment growth and subsequent growth and age at first spawning has implications for recruitment patterns of juveniles from different nursery areas and for the lifetime fecundity of population components with differential growth.