The relationship between spawning stock and recruitment for Atlantic cod stocks
Original version
This report is not to be cited without prior reference to the authorAbstract
The relationship between spawning stock biomass and recruitment in Atlantic cod stocks is
investigated by ranking the SSB values according to size and applying a moving average of
ten points. The resulting averages are plotted against the average recruitment produced by the
respective SSBs. The plot in most cases resembles a Beverton and Holt or Ricker type of
relationship, showing substantial reduction in mean recruitment at low levels of SSB even
though the relationship is not forced towards the origin. Applying a moving average of ten
years to the time series of data shows how SSB and recruitment relationships have developed.
For some stocks the apparent relationship might be explained by medium- or long-term
variation in the recruitment caused by environmental conditions. Considering all the available
data, there is nevertheless substantial evidence of reduced recruitment at low levels of SSB for
the cod.