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Fishing = Harvesting = Predation

Fishing = Harvesting = Predation. Predator-Prey Interaction +- with Humans as Predator Very high-tech hunting-gathering Fast boats Sonar, fish finders Factory on-board Midwater, bottom trawl Artisenal harvesting Coral reefs, intertidal. Exploited Populations.

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Fishing = Harvesting = Predation

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  1. Fishing = Harvesting = Predation • Predator-Prey Interaction +- with Humans as Predator • Very high-tech hunting-gathering • Fast boats • Sonar, fish finders • Factory on-board • Midwater, bottom trawl • Artisenal harvesting • Coral reefs, intertidal

  2. Exploited Populations • Sustainable or overexploited? • Small human populations: local depletion? • Deforestation of Med/Iceland • Oysters in Washington State • Now: • Larger human populations • Global markets and distribution • More people (# and %) in coastal zones

  3. Fishing MethodsCatch and Bycatch Fishing Effort: The total fishing gear in use for a specified period of time. Fishing Power: The catch which a particular gear or vessel takes from a given density of fish during a certain time interval. Bycatch: Unintended catch of organisms not part of the fishery being targeted.

  4. Peruvian Anchovy

  5. Peruvian Anchovy • Small fish, live 3yr, spawn 1yr, caught 5mo+ • School near surface • World’s largest fishery until 1972 • Major fishery started in 1955 • Catch doubled every year 1955-1961 • Peak 1971 @ 12.3mt, 18% total fish catch

  6. Peruvian Anchovy Cont’d • Maximum Sustainable Yield estimated at about 9 million tons/year • Assumes no change in environment • 1972 El Nino, no upwelling/nutrients • 1972 few young, lots of adults, huge catch • Crash of fishery, hasn’t recovered • Huge economic consequences

  7. Principles of Exploitation • Below certain levels, populations resilient – increase growth or survival to compensate for fishing losses (removal of indivs) • Above certain levels, local or global extinction of the resource ($ or actual) • Somewhere in middle, level of “maximum sustainable yield” – hard to apply in the real world • Social resilience and precautionary principle?

  8. Beyond Single-Species Approaches What about habitat, species interactions, climate change?

  9. A framework for fishing pressure

  10. Kinds of Bycatch • Fish of wrong (non-target) species • Fish that are of the wrong size • Fish that are of the wrong sex • Fish that are damaged (caused by gear or predation in the gear) • Excess fish discarded when quota reached • High-grading (low market value, damaged, or poor quality fish) • Prohibited species - any species which must by law be returned to the sea (i.e. marine mammals, turtles, birds, and other fish) • Population impacts vs economic benefit

  11. Some Solutions to Bycatch • Selective Fishing Gear • Turtle Excluder Devices (TEDs) • Deeper Longlines • Integrating Fisheries and Conservation • MPAs and BFFF • No take zones, goals? • Product certification

  12. Ecosystem Based Management • The effect of the environment on the resource (population biology and habitat!) • The effect of resource exploitation on the environment (food webs, energy) • Complex ecosystems, uncertainty, tipping points, and the precautionary principle • The human factor – fishing communities, cultures, practices, and economies

  13. Other Issues to Consider • Western Science vs Traditional Ecological Knowledge • Enforcement of Regulations and Rules • Markets and Externalities (ITQs) • Climate Change and Uncertainties of Oceans’ ability to produce fish • Social and ecological resilience, coupling!

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