Demersal Fish Explorations in the Northeastern Pacific Ocean — An Evaluation of Exploratory Fishing Methods and Analytical Approaches to Stock Size and Yield Forecasts

Abstract

A series of demersal fish studies were conducted throughout the northeast Pacific Ocean. The aims of these exploratory fishing surveys were: (1) to describe the zoogeographic distribution patterns of the animals encountered and the relationship of such patterns to observed environmental features; (2) to determine their relative abundance in time and space and to each other and their vulnerability to sampling gears; and (3) where possible, to establish approximations of the magnitude of important or potentially important commercial species together with estimates of the physical yields that these resources might provide. A general review is given of U.S. demersal fish explorations in the northeast Pacific Ocean along with the methodology employed. Methods for estimating standing stocks based on fish densities determined from catch-per-unit-of-effort data are given. Using this procedure, estimates have been made for the more abundant demersal fish forms in the northeast Pacific. Means of determining yield possibilities are suggested, based on natural mortality rates and standing stock sizes. This method assumes that the maximum sustainable catch will range from.4 to.5 of the virgin stock size times the natural mortality. Finally the authors evaluate the reliability of exploratory fishing surveys based on subsequent development of commercial fisheries in the northeast Pacific. The data appear to have provided a good basis for describing the distribution and availability of important demersal fish elements in this area. Although estimates of yield potentials are still being studied, the history of fisheries development has, to date, followed quite well what might have been expected as a result of the preliminary yield forecasts.