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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
Reports (PDF): FY
2007 (final rpt), FY
2006, FY 2005
The first intention of this project is to conduct data quality control studies with fishery observer and commercial logbook catch records for those pelagic management unit (PMU) species listed on the federal logbook form and taken by the Hawaii-based longline fishery but that have not yet been so evaluated. The underlying premise is that catch trends for all PMU species, not only those targeted or taken incidentally in substantial numbers, require consideration in the context of ecosystem-based fishery management. This premise is consistent with the interests in community dynamics, trophic relationships, or interactions among related taxa that were identified by Link et al. (2002) as suitable metrics for ecosystem status.
PMU species taken by the Hawai'i-based commercial longline fishery that have not yet been evaluated in terms of fishery observer and logbook data quality include skipjack tuna (Katsuwonus pelamis); bluefin tuna (Thunnus thynnus or T. maccoyii), sailfish (Istiophorus platypterus), black marlin (Makaira indica), oilfish (Lepidocybium flavobrunneum or Ruvettus pretiosus), mako sharks (Isurus spp.), thresher sharks (Alopias spp.), and oceanic white-tip shark (Carcharhinus longimanus). Silky shark (C. falciformis), though not listed on the logbook form, will be estimated from "Other sharks" by comparison to observer data.
The second intention of this project is to conduct exploratory analyses of catch data collected in the post-World- War-II era by U.S. Bureau of Commercial Fisheries (BCF) observers aboard Japanese commercial longline vessels. Catch records for 17 species (plus unidentified fishes) taken on 6355 longline sets from 1950 to 1951 and on 880 additional sets from 1952 to 1961 have been entered into the HL electronic data archive, with the associated positions and effort measurements including total hooks fished, total baskets fished, and hooks per basket. It is expected that exploratory analyses of these catch rates will prove comprehensible in light of a relatively small but relevant body of literature. For example, fishing operations aboard Japanese motherships in the post-World-War-II period were described by Shimada (1951a), Ego and Otsu (1952), and Van Campen (1952); longline catches by the expeditions during this period were summarized by Murphy and Otsu (1954); and biological observations including morphometrics and distributions of early life stages of tunas were summarized by Shimada (1951b). An additional historical review of Japanese fisheries in the Pacific Ocean and southeast Asian seas from the mid-19th century into the 1980s, with information on catches, effort, and legal, political, and economic factors that influenced fisheries development, was provided by Matsuda and Ouchi (1984).
The work to be conducted within this project, as with the current and preceding related activities, will contribute to increased accuracy in the observer and logbook catch data from the Hawaii-based longline fishery. As such, it should prove useful in fishery management for at least three specific reasons. First and probably foremost, it should prove beneficial for stock assessments by reducing the effects of errors and outliers in the catch data. A second potential benefit associated with enhanced data quality would be more meaningful evaluations of one or more of the ecosystem metrics recommended by Link (2002). For example, understanding of community dynamics should be enhanced by improved data quality in investigations of catch patterns relative to various types of fishing effort (i.e., tuna-directed, swordfish-directed) that exploit the water column differently and harvest distinct faunal assemblages . Also, improved data quality may prove particularly relevant in the case of "minor" species such as oilfish that at times comprise a substantial fraction (numerically) of the longline catch but tend not to be accurately reported in the logbooks. The third reason this project should prove valuable is that it should improve understanding of fishery monitoring per se because the Hawaii-based longline fishery operates under virtually ideal circumstances for such efforts, including substantial observer coverage (ca. 20%), a single sales outlet for the preponderance of all landings (the public auction conducted by the United Fishing Agency, Ltd., Honolulu, HI), and daily checks on vessel activity that have contributed to nearly full (ca. 99%) compliance with logbook reporting requirements. By completing evaluations of the accuracy, and by describing and estimating biases in catch data for all of the PMU species, this project should help to elucidate the species-specific accuracy that would represent "optimal" reporting, which is likely to vary in relation to monetary value, typical catch sizes, resemblance to other species, and perhaps other factors.
The exploratory analyses to be undertaken with data from the BCF in the post-World-War-II era, before the development of large-scale pelagic Pacific fisheries, should prove useful to fishery management by contributing to the development of meaningful retrospective comparison standards for more recent catch trends. Specifically, and in contrast to Myers and Worm (2003) who employed "community biomass" (i.e., pooled catch tabulations) as the response variable of interest, the intention is to generate species-specific descriptive and inferential statistical summaries. It is expected this may yield insight not only into catch rates, but also into operational techniques or other extrinsic factors that may have changed over time and led to changes in Pacific fisheries but which might not have become apparent in pooled analyses.
Year 1 funding for this 2-year project to be awarded in mid 2004.
Dr. William A. Walsh
National Marine Fisheries Service
PIFSC - Honolulu Laboratory
2570 Dole Street
Honolulu, Hawaii 96822 USA
Phone (808) 983-5346
FAX (808) 983-2902
This page updated January 8, 2008