Impact of Industrial Tuna Fisheries on Fish Stocks and the Ecosystem of the Pacific Ocean www.soest.hawaii.edu/pfrp/large_pelagics/large_pelagic_predators John Sibert John Hampton Pelagic Fisheries Research Program Oceanic Fisheries Programme University Hawaii Secretariat of the Pacific Community
Thanks to the folks who actually do the work: Adam Langley Pierre Kleiber Mark Maunder Shelton Harley Yukio Takeuchi Momoko Ichinokawa Tom Polacheck Alain Fonteneau Oceanic Fisheries Programme, SPC, Noumea NOAA Pacific Island Fisheries Science Center, Honolulu Inter-American Tropical Tuna Commission, La Jolla National Research Institute of Far Seas Fisheries, Shimizu CSIRO, Hobart IRD, Sete
Outline Preliminary results from an analysis synthesis exercise Based on stock assessment results using all available data Biomass trends Changes in size structure Changes in trophic structure within guild of top predators Regime shifts? Fishery management options Compare with results of simple CPUE analysis
Availability of stock assessments Current Assessments Needed Assessments Stock Status Stock Status WCPO Yellowfin 3 Ono 0 EPO Yellowfin 3 Mahi mahi 0 Southern Albacore 3 Oceanic Whitetip Shark 0 Northern Albacore 2 Pacific Bigeye 3 WCPO Bigeye 3 WCPO Skipjack 2 Pacific Swordfish 1 Pacific Blue Marlin 1 Pacific Blue Shark 1 3: current & definitive; 2: current, but needs work; 1: in progress or needs updating; 0: probably insufficient data Used in this presentation
Biomass Trends WCPO Yellowfin South Pacific Albacore Pacific Bigeye 0 500000 1500000 2500000 0e+00 1e+06 2e+06 3e+06 4e+06 0 1000000 2000000 3000000 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 1950 1960 1970 1980 1990 2000 EPO Yellowfin North Pacific Albacore WCPO Skipjack 0 500000 1500000 1950 1960 1970 1980 1990 2000 0 200000 600000 1000000 1950 1960 1970 1980 1990 2000 0.0e+00 4.0e+06 8.0e+06 1.2e+07 1950 1960 1970 1980 1990 2000
Impact of Fishery on Total Biomass Exploited/Unexploited 0.0 0.2 0.4 0.6 0.8 1.0 WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack 1960 1970 1980 1990 2000 Year
Changes in Size Spectra 0 500000 1500000 2500000 1950's 0 200000 600000 1000000 0 500000 1500000 2500000 1960's 0 200000 600000 1000000 0 500000 1500000 2500000 1970's 0 200000 600000 1000000 0 500000 1500000 2500000 1980's 0 200000 600000 1000000 0 500000 1500000 2500000 1990's 0 200000 600000 1000000 0 500000 1500000 2500000 2000's 0 200000 600000 1000000
Impact of Fishery on Size Proportional Biomass Reduction 0.0 0.2 0.4 0.6 0.8 1.0 Decade 1950s 1960s 1970s 1980s 1990s 2000s
Impact of Fishery on Spawning Biomass Exploited/Unexploited 0.0 0.2 0.4 0.6 0.8 1.0 WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack 1960 1970 1980 1990 2000 Year
Ecopath Calculations Central Pacific Eastern Tropical Pacific Cox et al., 2002 Olson & Watters, 2003 Species Small Weight (kg) Large Small Large Bigeye 3.82 39.0 123 4.06 4.53 80 5.17 Yellowfin 3.91 14.8 94 4.12 4.57 90 4.66 Albacore 3.96 13.3 87 4.10 4.60 Blue Shark 3.99 4.05 Blue Marlin 44.0 4.61 Swordfish 10.0 4.32 4.42 150 4.96 Skipjack 3.85 13.4 91 4.57 Marlins 5.22 150 5.32 Sharks 5.23 150 4.93 Bluefin 4.37 Sailfish 4.63 150 4.89 Average 3.91 4.21 4.77 4.83 Cox, S., S. Martell, C. Walters, T. Essington, J. Kitchell, C. Boggs, and I. Kaplan. 2002. Reconstructing ecosystem dynamics in the central Pacific Ocean, 1952-1998. I. Estimating population biomass and recruitment of tunas and billfishes. Can. J. Fish, Aquat. Sci. 59:1724-1735. Cox, S., T. Essington, J. Kitchell, S. Martell, C. Walters, C. Boggs, and I. Kaplan. 2002. Reconstructing ecosystem dynamics in the central Pacific Ocean, 1952-1998. II. A preliminary assessment of the trophic impacts of fishing and effects on tuna dynamics. Can. J. Fish, Aquat. Sci. 59:1736-1747. Olson, R. and G. Watters. 2003. A model of the pelagic ecosystem in the eastern tropical Pacific Ocean. IATTC Bulletin 22:135-218.
Eastern and Western Food Webs Hinke, J, I. Kaplan, K. Aydin, G. Watters, R. Olson and J. Kitchell. 2004. Visualizing the food-web effects of fishing for tunas in the Pacific Ocean. Ecology and Society 9:1-10. http://www.ecologyandsociety.org/vol9/iss1/art10
Eating your way to the top 3.0 3.5 4.0 4.5 5.0 + 3.0 3.5 4.0 4.5 5.0 + http://www.flmnh.ufl.edu/fish/gallery/descript/yellowfintuna/yellowfintuna.html
Trophic Transitions Ecopath Switch + Stock WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack + Stock WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack Ontogenetic + Stock WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack + Stock WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack Central Pacific Eastern Tropical Pacific
Impact of Fishery on (1) 0e+00 2e+07 4e+07 1950's 0.0e+00 6.0e+06 1.2e+07 0e+00 2e+07 4e+07 1980's 0.0e+00 6.0e+06 1.2e+07 0e+00 2e+07 4e+07 1960's 0.0e+00 6.0e+06 1.2e+07 0e+00 2e+07 4e+07 1990's 0.0e+00 6.0e+06 1.2e+07 0e+00 2e+07 4e+07 1970's 0.0e+00 6.0e+06 1.2e+07 0e+00 2e+07 4e+07 2000's 0.0e+00 6.0e+06 1.2e+07 WCPO Ontogentic
Impact of Fishery on (2) 0.0e+00 6.0e+07 1.2e+08 1950's 0.0e+00 1.5e+07 0.0e+00 6.0e+07 1.2e+08 1980's 0.0e+00 1.5e+07 0.0e+00 6.0e+07 1.2e+08 1960's 0.0e+00 1.5e+07 0.0e+00 6.0e+07 1.2e+08 1990's 0.0e+00 1.5e+07 0.0e+00 6.0e+07 1.2e+08 1970's 0.0e+00 1.5e+07 0.0e+00 6.0e+07 1.2e+08 2000's 0.0e+00 1.5e+07 EPO Switch
Impact of Ecosystem on Fishery Recruitment Anomaly Darwin Tahiti SOI 2 1 0 1 2 2 1 0 1 2 WCPO Yellowfin EPO Yellowfin South Pacific Albacore North Pacific Albacore Pacific Bigeye WCPO Skipjack 5 year centered average 59 month leading average 1950 1960 1970 1980 1990 2000 Year
Conclusions Impact of fisheries on biomass is variable Expansion of the purse seine fishery has extended fishing mortality to all age classes of some species Some stocks have declined to a point where management intervention is required Some stocks appear to have increased in abundance Fish larger than 150cm have declined to about 20% of their predicted abundance in the absence of fishing Impact on trophic structure within the guild of top predators is not detectable Fishery-independent trends in recruitment and biomass are apparent Estimated increase in skipjack biomass consistent with predictions from food web models Future work Increase number of stocks in analysis Extend skipjack stock assessment to include 1952-1974 Examine possibilities for assessments of mahi mahi, ono, and small tunas
Fishery Management Options United States Domestic: For yellowfin and bigeye F > M MSY (overfishing is occurring), but B > B MSY (stocks are not overfished) US catch comprises approximately 0.5% longline and 5% purse seine yellowfin catch US longline bigeye catch comprises approximately 1% total longline bigeye catch Unilateral measures by US would be futile International IATTC - measures to reduce mortality on bigeye ineffective to date WCPFC - identified potentially effective management options Reduce fishing effort by all fleets by 15% Shift purse seine effort away from FAD sets to school sets May implement measures at second meeting in December 2005
The Claims... large predatory fish biomass today is only about 10% of preindustrial levels. Ransom A. Myers and Boris Worm. 2002. Rapid worldwide depletion of predatory fish communities Nature 423:280-283. I know that the human being and the fish can coexist. George W. Bush CPUE is not a reliable index of abundance Community CPUE a bogus concept Omits of most of data
Interpretation of Catch per Unit Effort (1) Albacore South of the Equator CPUE (Fish/100 Hooks) 0 1 2 3 4 Japan Taiwan 1950 1960 1970 1980 1990 2000 Year Hampton, J, J. Sibert, P. Kleiber, M. Maunder, S. Harley. 2005. Decline of Pacific tuna populations exaggerated? Nature 434:E1-E2.
Interpretation of Catch per Unit Effort (2) _ Yellowfin South of 10 South CPUE (Fish/100 Hooks) 0 1 2 3 4 5 6 35% Decline by 2900 tonne removal 60% Decline by 8900 tonne removal 0 5000 10000 Total 1950 1960 1970 1980 1990 2000 Year Yellowfin Between 10 South and 10 North CPUE (Fish/100 Hooks) 0.0 1.0 2.0 1950 1960 1970 1980 1990 2000 Year 0e+00 2e+05 4e+05 Total
Selective use of data (1)
Selective use of data (2)