Comparisons of Catch Rates for Target and Incidentally Taken Fishes in Widely Separated Areas of the Pacific Ocean

Progress Reports (PDF): FY 2005, FY 2004, FY 2003

Project Overview
Project investigators will conduct statistical research to elucidate variation across very broad spatial scales in catch per unit effort (CPUE) for several widely distributed Pacific fishes as a contribution to the development of ecosystem-based fishery management. Ecosytem-based fishery management refers to practices that incorporate the best available information concerning the biology of the species of interest, including physiological capacities, predator-prey relationships, population genetics and distributions, the physicochemical characteristics of the environment at scales up to and including Pacific basin-wide, and the effects of human intervention on both the species of interest and the environment itself.

While extensive research has been done on the variation in marine fish catch rates across very broad spatial scales, those studies did not present a statistical model that might have permitted assessment of the effects of individual operational or environmental factors on CPUE. Recent studies have begun to evaluate the relationships between global climatic factors and production of several major fish taxa in widely separated locales. The development and advances in remote sensing methodologies have also engendered the capability to relate oceanographic processes to more localized biological phenomena. Project researchers hope to incorporate ecologically and oceanographically meaningful variables into statistical models of catch rates. The intent of this research is to determine whether, and to what extent, intra- and interspecific CPUE for several species are correlated throughout the Pacific Ocean. This will entail analyses and comparisons of fish catch and operational data from Pacific-region longline logbook records and fishery records, as well as incorporation into the statistical analyses of a suite of remotely sensed oceanographic variables. It is anticipated that the development and application of improved statistical models of catch rates, with the planned incorporation of remotely sensed oceanographic data, should represent a useful conceptual contribution to ecosystem-based fishery management, while careful evaluation of data obtained from the various sources should prove useful from a practical perspective.

The main objectives of this project are as follows:

1. To contribute to improved management of the species of interest by developing statistical models to characterize the effects of oceanographic and operational factors on catch rates. To fit generalized additive models (GAMs) to updated data from the Hawai'i Longline Observer Program including incorporation and interpretation of remotely sensed oceanographic variables.
2. To apply these statistical models to data from the Hawai'i-based longline and other Pacific-region fisheries in the expectation that catch rates may exhibit different patterns of variation in response to the different levels of the predictor variables likely to be associated with widely dispersed fisheries.
3. To contribute to improved management of these species in American Samoa and other U.S.-controlled fisheries by facilitating the organization and implementation of a longline logbook program.
4. To investigate the use of statistical models as sources of reference points for assessment of CPUE trends. The intention is to determine whether output from the GAMs, including both the corrected CPUE trends and the partial residuals and smoother plots from the predictors, can serve as useful 'early warning' indicators that fishery managers could employ to gauge the need for intervention.
5. To perform exploratory analyses of trolling data from the U.S.-controlled western Pacific fisheries, as presented by the NMFS Western Pacific Fishery Information Network (WPACFIN), by the same statistical procedures as will be used with the longline fisheries data.

The fishes of interest to this project include both target and incidentally caught species that are individually important ecologically and/or economically, as recreational fishes, or for some combination of these reasons. The candidate species include three tunas (albacore, Thunnus alalunga, bigeye, Thunnus obesus, and yellowfin tuna, Thunnus albacares), dolphin (known in Hawaii as mahimahi), Coryphaena hippurus, wahoo, Acanthocybium solandri, blue marlin, striped marlin and shortbill spearfish, Tetrapturus istiophorus. Swordfish data will be analyzed in case technical or legal developments permit the resumption of a targeted fishery in the future. Because fishery statistics may be unavailable or limited in scope, comparisons will be limited to those sources that can provide sufficient data.

Year 1 funding for this 2-year project to be awarded in November 2002.