both countries, initial fisheries management plans were simply a continuation of a course that had been set by ICNAF. Even today the United States and Canada use the same statistical areas and definitions that were defined in the early 1950s. Except for refinements in statistical procedures, longer data series, the attention to some new species, and much more complete recording of fishing mortality, essentially the same methodology—certainly the same fundamental theory—is still used to assess the status of each stock and reach recommendations about acceptable levels of catch.

The most significant inheritance from the international era, however, was and is the scientific approach that simplifies the reality of complex ocean systems by treating each individual species as if it were an independent or isolated entity. The core of single-species theory is the belief that the future size of individual stocks is strongly related to spawning stock biomass, which, in turn, is strongly determined by how much fishing occurs. The relationship between fishing and spawning stock size is clear and easy to measure. But the theorized relationship between the spawning stock and recruitment is generally unknown and only claimed to exist for a few stocks, and then only at very low population sizes (Hall, 1988; Myers et al., 1995).4 In spite of the absence of confirming evidence, fisheries scientists are firmly convinced that the sustainability of each population depends on the maintenance of an adequate spawning stock biomass.

Consequently, in the day-to-day management of fisheries, there is no attempt to predict recruitment. It is simply hoped, or assumed, that recruitment will proceed at a rate that is close to the average for some recent time period—one or two decades. Fisheries scientists advise managers about desirable catch rates, or amounts, in terms of what they estimate will produce the best yield from the year classes already in the water while maintaining a reasonable level of spawning stock biomass. There is an implicit but strong assumption that ecological interactions are minimal and not disturbed in any fundamental way by simultaneously fishing all or many species at moderate or even high rates. In addition, there are very difficult measurement and estimation problems. Errors of measurement on the order of 30 to 50 percent are common (Hilborn and Walters, 1992; Walters, 1998). As William Fox, science director of the National Marine Fisheries Service (NMFS), puts it, “there’s a bit of experience involved, not something that can be repeated by another scientist. It’s not really science; it’s like an artist doing it—so a large part of your scientific advice comes from art” (Appell, 2001). Most fisheries scientists are reasonably well aware of the shortcomings of the theory and uncertainties regarding measurements and estimates of population size.


When these uncertainties became apparent in the early years of extended jurisdiction, they were met by a few interested parties in the fishing industry with honest expressions of skepticism and, more commonly, with gaming strategies

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement