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Analyses of Catch Data for Mahimahi (Coryphaena hippurus) and Wahoo (Acanthocybium solandri) from the Hawaii-Based Longline Fishery and Other Pacific Fisheries

Progress Reports (PDF):
FY2010, FY 2009

Project Overview
This proposal describes biometrical research with two species of mid-sized, epipelagic predatory fishes of substantial economic importance and considerable ecological interest to the Hawaiibased longline fishery. Although taken primarily as incidental catch, dolphinfish, Coryphaena hippurus, known in Hawaii and other Pacific locales as mahimahi, and wahoo, Acanthocybium solandri, accounted for at least 3.8% and 1.7%, respectively, of the total value of longline-caught fishes in Hawaii in 2007 (Hawaii Division of Aquatic Resources 2008). In the context of ecosystem-based management, these are fast growing, very widely distributed species that may serve as indicators of the status and sustainability of certain pelagic fisheries. If, for example, large predatory fishes (e.g., adult tunas, marlins, swordfish, sharks) were overfished or subject to overfishing, a proliferation of mid-sized predators with an associated increase in catch rates might be expected. This project should yield the sort of basic, background information about these mid-sized species that will permit fishery managers and scientists to identify any such trend(s). This project will entail investigation of catch rates (catch-per-unit of effort; CPUE), landings, and sizes of mahimahi and wahoo from several fisheries and locales, drawing upon data of several types from several sources. The null hypotheses of primary interest are that these response variables have not changed significantly over time within fisheries and regions, do not differ significantly between locales within types of fisheries, and do not differ significantly between types of fisheries within locales. As such, this project will not be purely longline-oriented, as has been the case previously (see Linkage to Other PFRP Projects, below), but should be of more general interest

There are four objectives for this project. Two will involve detailed analyses of catch data from the Hawaii-based pelagic longline fishery. The others will involve comparisons of catch data from the troll fishery in Hawaii, and from the Hawaii-based longline fishery and those in other Pacific locales. Primary data sources will be the NOAA Fisheries logbooks and observer data, the Hawaii Division of Aquatic Resources (HDAR), and the Western Pacific Fisheries Information Network (WPACFIN). Available time series include 2007.

The first objective will be to develop statistical models of catch rates for mahimahi and wahoo from the Pacific Islands Regional Observer Program catch data and then apply the model coefficients to the logbook data from the Hawaii-based longline fishery in order to identify outliers associated with reporting biases. This will increase the number and types of species with corrected, well-documented catch histories in the data archives of the Pacific Islands Fisheries Science Center.

The second objective is to determine whether, and if so, to what extent, intraspecific CPUEs for these species are correlated in various regions of the Pacific Ocean. This will entail comparisons of mahimahi and wahoo catch rates from several fisheries by use of appropriate correlation and time series techniques. Likely data sources, in addition to the Hawaii-based longline fishery, include troll data from the Hawaii Division of Aquatic Resources, offshore creel survey records from the Guam Division of Aquatic and Wildlife Resources, observer and longline logbook records from American Samoa, and offshore creel records from American Samoa.

The third objective will be to use the corrected CPUE trends from the Hawaii-based longline fishery to test predictions from ecosystem models (ECOSIM, ECOSPACE) for the North Pacific Ocean. These models suggest that fishes at lower trophic levels (e.g., mahimahi, wahoo) would exhibit compensatory responses to declines in higher trophic level predators (e.g. blue marlin, yellowfin tuna, blue shark). In this context, it is considered appropriate to use a one-sided alternative of significant increase relative to the null hypothesis of no significant temporal changes in CPUE.

The fourth objective will be to identify and estimate patterns in the sizes of these fishes. In the case of the Hawaii-based longline and commercial troll fisheries, individual weights of each fish sold at the United Fishing Agency public fish auction since January 1, 2000 will be available.

Linkages to Other PFRP Projects
This project represents an extension of “Investigation of Shark Bycatch in the Hawaii-based Longline Fishery, and an Extension of Analyses of Catch Data from Widely Separated Areas in the Pacific Ocean”, with William A Walsh and Keith A. Bigelow as principal investigators. Wahoo and mahimahi were among the species chosen for comparative purposes. Some work has been completed, with preliminary results presented at the 58th International Tuna Conference in Lake Arrowhead, CA, in May 2007 (“Exploratory Analyses of Mahimahi and Wahoo Catch Rates in the Hawaii-based Longline Fishery”, by William A. Walsh and Keith A. Bigelow). The detailed spatiotemporal comparisons called for have not yet been conducted.

This project is directly linked to four previous projects (listed below) that featured statistical analyses of catch data for several types of fishes. Results from these projects included evaluations of the accuracy of observer and commercial logbook data, identification and estimation of biases associated with self-reporting, and establishment of a research database with corrected estimates of catch totals and removals. This project will represent a meaningful enhancement to the earlier projects by providing thorough analyses of mid-sized predatory fishes and by identifying similarities or differences among fisheries and locales. By so doing, this should yield insight into spatiotemporal sources of variation in catch time series.

"Distributions, Histories, and Recent Catch Trends with Six Fish Taxa Taken as Incidental Catch by the Hawaii-based Commercial Longline Fishery.” PIs: William A. Walsh and Samuel G. Pooley. Project completed: FY 2002.

Comparisons of Catch Rates for Target and Incidentally Taken Fishes in Widely Separated Areas of the Pacific Ocean.” PIs: William A. Walsh and Keith A. Bigelow. Project completed FY 2004.

Evaluation of Data Quality for Catches of Several Pelagic Management Unit Species by Hawaii-based Longline Vessels and Exploratory Analyses of Historical Catch Records from Japanese Longline Vessels.” PIs: William A. Walsh and Keith A. Bigelow. Project completed FY 2006.

Investigation of Shark Bycatch in the Hawaii-based Longline Fishery, and an Extension of Analyses of Catch Data from Widely Separated Areas in the Pacific Ocean.” PIs: William A. Walsh and Keith A. Bigelow. Funding date: September 2006. In progress

Funding received November 2008.


Project Investigator:
Dr. William A. Walsh
National Marine Fisheries Service
Honolulu Laboratory
2570 Dole Street, Room 212
Honolulu, Hawaii 96822
Phone (808) 983-5346
FAX (808) 983-2902
email: William.Walsh@noaa.gov

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This page updated September 27, 2010