Evaluating the science behind the management advice for North Sea cod

Since 1974, annual assessments have constituted the core of the scientific advice underpinning management of the North Sea cod stock. Here, we base our evaluation of the assessments' performance on the quality of the advice and on the wider issue of how science is used to produce management advice. At the same time, we consider catch-at-age analyses and catch forecasts in the context of the amount of person-time and expertise available at the relevant working group meetings. The results indicate that, generally, the catch forecasts have been positively biased and that the bias has been driven by three main factors: (i) substantial overestimates of terminal stock size since the late 1990s, (ii) overestimates of incoming recruitment, and (iii) overestimates of growth. Information for other North Sea stocks (haddock, plaice, and sole) suggests that bias is a problem generally, not one unique to cod. Our results include a discussion of ways to use science more effectively in supplying management advice.