Transcript Fisheries I
Fisheries Fish as Food Commercial Fisheries Trends in World Fisheries Solutions? Commercial Fisheries • • • • • • Traps Trawls Purse seines Gillnets Longlines etc… Purse seining Trawling Fish size-selective grid Cod Fishery - Norway Gillnetting Longlining Technological Improvement in Fisheries Tuna catches under floating objects World Fishing Fleet Capacity 40 30 Non corrected 20 10 2000 1990 1980 1970 0 1960 Gross Registered Tonnage (106 tons) Corrected Production of Marine Fisheries 100 Capture Million tonnes 80 60 40 20 mariculture 0 1950 1960 1970 1980 1990 2000 EEZs Claims Production ( million tonnes) Global Trend in Landings 100 50 1800 1840 1880 Year 1920 1960 2000 Catches per 100 hooks (Japanese fleet) 1952 1964 1958 1980 Myers & Worm, 2003 Development Phases of World Fisheries Phase IV Senescent 90% 80% 70% Phase III Mature 60% 50% 40% Phase II Developing 30% 20% Phase I Undeveloped 10% 1993 1991 1989 1987 1985 1983 1981 1979 1977 1975 1973 1971 1969 1967 1965 1963 1961 1959 1957 1955 1953 0% 1951 Percentage of resources 100% State of Fish Stocks 1999 Recovering Depleted Overexploited Fully exploited Moderately exploited Undeveloped 0% 10% 20% 30% 40% 50% Trends in States of Fish Stocks 60% Fully Fished 50% 40% Moderately fished: U+M 30% 20% Overfished: O+D+R 10% 0% 1970 1975 1980 1985 1990 1995 2000 2005 Ratio between Present & Historical Landings 1. Antarctic 2. Atlantic, Southeast 3. Pacific, Southeast 4. Atlantic, Northwest 5. Atlantic, Western Central 6. Pacific, Eastern Central 7. Medit . & Black Sea 8. Pacific, Northeast 9. Atlantic Southwest 10. Atlantic Eastern Central 11. Atlantic Northeast 12. Indian Western 13. Pacific Central Western 14. Pacific Southwest 15. Pacific Northwest 16. Indian Eastern 0.14 ANT 0.39 ASE 0.43 PSE 0.44 ANW 0.71 ACW 0.73 PEC 0.81 MBS 0.83 PNE ASW 0.86 AEC 0.87 ANE 0.92 0.94 IW PCW 1.00 PSW 1.00 PNW 1.00 IE 1.00 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Population Size (N) Maximum Sustainable Yield = Growth = Maximum Sustainable Yield Time (t) Growth / Yield Maximum Sustainable Yield Fishing effort Simple Abundance Model Single Species Models • Assessment models are biased because they do not incorporate the predation by other species. • Assessment models are limited because of their emphasis on equilibrium solutions, such as MSY. • Assessment models do not usually account for environmental changes, whether interannual or interdecadal. • A correct assessment approach requires that a multi-species framework be used. • Harvest recommendations from single-species assessment do not consider the needs of other species. • Harvest recommendations from single-species assessment involve the deliberate fishing down of a population and therefore adversely change the ecosystem. • The single-species approach is invalidated, because overfishing has occurred for at least a majority of the world’s fisheries. • Single-species approaches do not account for the indirect effects of fishing (e.g. bottom fishing on habitat quality). Fishing at MSY level: is it good or bad? 0% 50% 100 PSE 50% PEC “BAD” AEC ANT ANT PCW ANE PNW ASW IE PNE ANW PNW ASW ACW MBS PEC ANE “GOOD” ASE ANW AEC PCW PSE IW IW PSW ACW A: if fishing at MSY is “good” “GOOD” PSW MBS IE 100 % “BAD” B: if fishing at MSY is “bad” Neoclassical Sustainability Modern Sustainability Fishery induced changes in world fish composition Fishing Down the Food Web Shark Populations NE Atlantic Baum et al. 2003 • Fisheries have significantly contributed to human development and can still do so • There are problem areas and avenues for positive change • Change will never be at no cost; but…. Solutions? Historical Succession of Coastal Ecosystems 1. Over-exploitation of large predators 2. Collapse “Ecosystem Engineering” species 3. Rise of Microbes Jackson et al. 2001 Historical fishing consequences Jackson et al. 2001 Historical fishing consequences Jackson et al. 2001 Historical fishing consequences Jackson et al. 2001 Jackson et al. 2001