Uncertainty is of paramount importance in fisheries (Smith 1994). Virtually everything about a specific marine population is poorly known; some aspects may be almost completely unknown, even for important species with long histories of fishing. Past and present stock abundance, and biological characteristics such as growth, natural mortality and reproductive rates, though important to management decisions, are usually highly uncertain. Likewise, many details of ecosystem structure and the potential consequences of severely reducing target species, are largely unknown—some would say unknowable.

It is surprising, therefore, that until quite recently uncertainty and risk have been all but neglected in formulating scientific advice for management. The traditional paradigm, Maximum Sustained Yield (MSY), which dominated science-based management for many decades, was eventually modified marginally (for example, to the F0.1 criterion commonly used in the 1970s–80s) to allow for unspecified uncertainty. But how to deal explicitly with uncertainty remained itself uncertain. Fishery managers often seemed to be interested only in the scientists' “best estimates” of the current Total Allowable Catch (TAC), and this was sometimes over ruled on political or economic grounds, namely because the proposed TAC was too small to satisfy the needs of the existing fleet.

By the early 1990s several major fisheries that had been under intensive management suffered severe stock collapses. These failures prompted many scientists to re-examine the whole question of risk and uncertainty in fisheries management.