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Recent Progress in Analyses of Catch Data from Fishery Observers and In

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Recent Progress in Analyses of Catch Data from Fishery Observers and In Preliminary Results from Analyses of Shark Catches in the Hawaii-based Longline Fishery as Reported by Fishery Observers William A. Walsh University of Hawaii Joint Institute for Marine and Atmospheric Research Pelagic Fisheries Research Program Keith A. Bigelow NOAA Fisheries Pacific Islands Fisheries Science Center Background • Ms. Kitty Simonds (Chair, WPRFMC) wrote to Dr. Samuel G. Pooley (Science Director, PIFSC) in January 2006 concerning the need for sharks research in this longline fishery • Sharks comprised most of the officially reported bycatch (ca. 90%) and a substantial fraction of the total catch (ca. 15%) in 2004 • Complexities associated with management measures during study period Objectives • Describe and quantify species composition of the sharks catch of this fishery • Assess the accuracy of species identifications by observers • Model survivorship of sharks taken on longline gear • Estimate catches and catch rates for sharks reported in commercial logbooks • Identify and describe apparent effects (if any) of management measures on self-reporting practices Species of Major Interest: Blue Shark Blue shark (Prionace glauca) Species of Major Interest : Requiem Sharks Silky shark Oceanic whitetip shark (Carcharhinus falciformis) (Carcharhinus longimanus) Species of Major Interest: Thresher Sharks Bigeye thresher Pelagic thresher (Alopias superciliosus) (Alopias pelagicus) Species of Major Interest: Makos Shortfin mako Longfin mako (Isurus oxyrinchus)(Isurus paucus) Current Activities: Observer Catch Data • Definition of a corrected sharks species list • Characterization of the importance and relative abundance of shark species taken in this fishery • Determination of set type (i.e., deep vs. shallow) effects on catch patterns for sharks • Investigation of factors that may be related to survivorship of sharks on longline gear Species Identifications Shark Identifications and Observer Experience Shark Catch: Taxonomic Composition • Diversity: 3 orders, 8 families, 13 genera, 23 species • Carcharhiniformes: 2 families, 4 genera, 11 species • Lamniformes: 5 families, 7 genera, 10 species • Squaliformes: 1 family, 2 genera, 2 species Shark Catch: Major Species • Blue shark: 87.0%; 6.3/set; 3.6/1000 hooks • Bigeye thresher shark: 3.8%; 0.3/set; 0.2/1000 hooks • Oceanic whitetip shark: 3.1%; 0.2/ set; 0.1/1000 hooks • Shortfin mako: 2.6%; 0.2/set; 0.1/1000 hooks • Silky shark: 1.5%; 0.1/set; < 0.1/1000 hooks • Crocodile shark: 1.0%; < 0.1/set; < 0.1/1000 hooks Shark Catch: Set-type Effects Shallow Sets • Blue shark: 93.5%; 11.7/set; 14.2/1000 hooks • Shortfin mako: 3.6%; 0.5/set; 0.6/1000 hooks • Oceanic whitetip shark: 1.7%; 0.2/set; 0.3/1000 hooks Deep Sets • Blue shark: 84.0%; 5.1/set; 2.6/1000 hooks • Bigeye thresher shark: 5.5%; 0.3/set; 0.2/1000 hooks • Oceanic whitetip shark: 3.8%; 0.2/set; 0.1/1000 hooks Shark Survivorship: Set-type Effects Shallow Sets Deep Sets • Blue shark 95.0% 96.7% • Shortfin mako 75.8% 80.7% • Oceanic whitetip shark 92.3% 80.6% • Silky shark (N < 50) 74.8% • Bigeye thresher shark 70.0% 82.4% • Crocodile shark (N < 50) 96.7% Soak Time Effect on Survivorship Blue shark ps.out.000 SST Effect on Survivorship Blue shark Blue shark Soak Time Effect on Survivorship Bigeye thresher shark Bigeye thresher sharkBigeye thresher shark SST Effect on Survivorship Bigeye thresher shark Bigeye thresher sharkBigeye thresher shark Bigeye thresherBi shark Near-term Tasks • Complete checks on observer catch data • Complete fitting logistic regressions and check partial residuals • Tabulate biological information for major species (e.g., sizes, sex ratios, maturity) • Compute morphometric regressions for major species Acknowledgments • Christofer Boggs, Dean Grubbs, Kim Holland, Russell Ito, Kurt Kawamoto, Walter Machado, John Naughton and Michael Seki provided useful comments concerning sharks in this longline fishery. S. Joseph Arceneaux, Joseph O’Malley, Thomas Swenarton, and Jeremy Willson commented on the role of fishery observers. Shark photographs were provided by the Hawaii Longline Observer Program archive. Deborah H. Yamaguchi assisted with this PowerPoint presentation. • This work was supported by NOAA Cooperative Agreement No. NA17RJ1230..
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