Tagged tuna graphic by Nancy Hulbirt, SOEST Illustration.

PFRP Statistics & Modeling Projects

Analyses of Catch Data for Blue and Striped Marlins (Istiophoridae)

Progress Reports: FY 2012, FY 2011

Project Background

Blue Marlin Stock Assessment Preparations
The RFP lists preparation for a blue marlin stock assessment as a priority item. This project, which is intended to contribute to such preparations, will entail collaborative research by a PFRP-affiliated researcher (WW) with extensive experience concerning this species in the Hawaii-based longline fishery and a senior NOAA Fisheries scientist (JB) who will work on the assessment.

Walsh et al. (2005) analyzed logbook accuracy and presented a corrected catch history for blue marlin from March 1994 through June 2002 in the Hawaii-based l ongline fishery, as well as an update through February 2004 (Walsh et al. 2007). All of this work was based upon integrated use of catch data from the Pacific Islands Regional Observer Program (PIROP), commercial longline logbooks submitted to the Pacific Islands Fisheries Science Center (PIFSC) and sales data from the Hawaii Division of Aquatic Resources (HDAR). As a result of these studies, reporting patterns and sources of bias in catch data for blue marlin have been described and the associated ramifications quantified.

The intentions at this time are to provide an updated corrected catch history and indices of relative abundance that correspond to the current management regime of the fishery (i.e., two sectors). Such indices should prove useful to the Stock Assessment Division at the PIFSC in preparation for the upcoming stock assessment planned for 2012 to be conducted under the aegis of the Interim Scientific Committee Billfishes Working Group (ISCBFWG). Whereas the published analyses (Walsh et al. 2005; 2007) relied upon use of generalized additive models (GAMs), this project will include methodological improvements because both GAM and generalized linear model (GLM) analyses will be conducted with a longer time series to provide the relative abundance indices. The collaborative nature of the project should also ensure that the applicability of the analyses to the preparation for the stock assessment is maximized. This work may also facilitate participation by other scientists supported by the PFRP. Problems with data access and quality may be minimized by the lead author's (WW) familiarity with blue marlin catch data from both the PIROP and the logbooks and ability to provide corrected data sets subject to NOAA Fisheries confidentiality requirements.

Striped Marlin as Incidental Catch and Stock Assessment Preparations
The RFP lists striped marlin as important incidental catch species in the Hawaii-based pelagic longline fishery. This species is of concern because its stock status may be seriously depleted. Although cited above in reference to blue marlin (Walsh et al. 2005; 2007), the PFRP-supported work described in these documents also contributed to improved understanding of the distribution, seasonality and relative abundance of striped marlin. The reason is that misidentifications of striped marlin as blue and vice versa have been a problem of longstanding in monitoring this fishery.

As with blue marlin, the intentions are to provide an updated corrected catch history and indices of relative abundance that correspond to the current management regime of the fishery (i.e., two sectors). The relative abundance indices and corrected data should prove useful to the Stock Assessment Division at the PIFSC in preparation for the next striped marlin assessment because both were used in the most recent assessment.

Description of Work

Analyses of catch data for both species will be predicated upon integrated use of fishery observer reports, longline logbooks and commercial sales data. The observer records represent the data source previously used to fit GAMs according to methods described in Walsh et al. (2005; 2007). The logbooks represent the data to which fitted model coefficients are applied and the sales records are used to verify inferences regarding apparent qualitative or quantitative discrepancies between predicted and observed catches.

The work will entail fitting a GAM and a GLM for each species. The indices of relative abundance computed with these models will be compared to each other and to the nominal CPUE trends from the two fishery sectors.

The corrections to the marlins catch data in the logbooks will be archived in a research database at the PIFSC. The earlier marlins work has been saved in this format.

Funding for this project to be available late 2010.

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References

International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean. 2007. Report of the Marlin and Swordfish Working Group Joint Workshop. March 19-26, 2007, Taipei, Taiwan.

Walsh, W.A., K.A. Bigelow and R.Y. Ito. 2007. Corrected catch histories and logbook accuracy for billfishes (Istiophoridae) in the Hawaii-based longline fishery. U.S. Department of Commerce. NOAA Technical Memorandum NMFS-PIFSC-13. 39 pp.

Walsh, W.A., R.Y. Ito, K.E. Kawamoto and M. McCracken. 2005. Analysis of logbook accuracy for blue marlin (Makaira nigricans) in the Hawaii-based longline fishery with a generalized additive model and commercial sales data. Fisheries Research 75:175-192.

Principal Investigators

Dr. William Walsh
National Marine Fisheries Service
Pacific Isles Fisheries Science Center
2570 Dole Street
Honolulu, Hawaii 96822 USA
Phone (808) 983-5346
FAX (808) 983-2902
email: William.Walsh@noaa.gov

Dr. Jon Brodziak
National Marine Fisheries Service
Pacific Isles Fisheries Science Center
2570 Dole Street
Honolulu, Hawaii 96822 USA
Phone (808) 983-2964
FAX (808) 983-2902
email: Jon.Brodziak@noaa.gov

 

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