A recent synthesis and development of the literature by Smith (1969) has greatly increased the power and generality of the economic theory of commercial fishing. In contrasting his own analysis with previous work, Smith suggests that the most serious deficiency in the received doctrine is that it "is not able to handle the situation in which a species may be exploited to the point of extinction. The theory implies that short of zero unit costs the equilibrium yield to competitive exploitation is never zero with an extinct population." As Smith observes, evaluation of this implication depends on whether one believes that commercial fishing has ever, or could ever, cause the extinction of a fishery a matter over which there is some controversy.' The theoretical question is one of importance from both positive and normative points of view. On the one hand, it would appear that, if convincing evidence of commercial extinction were discovered, then the received theory of fishing would be decisively refuted. On the other hand, policy makers cannot wait indefinitely for the results of future research, especially when concerned with irreversible changes such as the extinction of species. Their attitudes toward proposals for the regulation of fishing are bound to be colored by untested conclusions of current theory. For these reasons, it would seem important to reexamine the inference which Smith draws from the received theory, particularly because Smith does not explain which features of the theory are responsible for his conclusion.