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Oceans 11

Over Fishing. Oceans 11. What is “fishing”?. Exploitation of marine organisms for sustenance, profit, or fun. Examples: Fish- cod, halibut, salmon, redfish, stripped bass… Shellfish Mollusks- clams, scallops, oysters, abalone… Crustaceans- crabs, shrimp, lobster… Reptiles- turtles

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Oceans 11

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  1. Over Fishing Oceans 11

  2. What is “fishing”? • Exploitation of marine organisms for sustenance, profit, or fun. • Examples: • Fish- cod, halibut, salmon, redfish, stripped bass… • Shellfish • Mollusks- clams, scallops, oysters, abalone… • Crustaceans- crabs, shrimp, lobster… • Reptiles- turtles • Mammals- whales

  3. Why do we fish? • Survival- many costal communities, particularly in developing countries, fish as a primary food source. • Recreation- fishing for fun. • Profit- commercial exploitation as a means of earning a livelihood.

  4. What are some of the effects of fishing on humans? • Sociology- in some places people need to fish to survive, in many others they simply want to fish as a mode of recreation. • Economics- individuals and regions can be dependent on fishing as a source of income. • Ecology- natural systems are easily disrupted by fishing.

  5. What is “over fishing”? • Removal of organisms from the marine environment by humans at a rate which cannot be sustained by the local ecosystem and therefore significantly alters natural ecosystem. or • Fishing a population faster than it can replace itself; the population decreases in size as a result.

  6. How big is the problem? • The world marine catch is nearly 100 million tonnes per year. • 27 millon tonnes of by-catch (almost 1/3 of total catch) is thrown back dead into the ocean Larger shrimps fetch a higher price, there is an incentive for discarding smaller fish as shown left.

  7. What are some consequences of over fishing? • Much more complicated than reduction of one species • Trophic interactions • Examples: Salmon, killer whale, sea otter • Change in ecosystem structure • Loss of biodiversity

  8. Consequences…By - Catch! By-catch is all non-target species caught with target species whether retained then sold or discarded • One example of by-catch is dolphins caught in tuna nets. • Often a problem with widespread use of unselective fishing gear • Bottom trawling disturbs everything on the ocean floor

  9. Collapse of the North Atlantic Cod Fishery • Canadian cod stock severely depleted by local and distant water fleets • Canada declared Extended Fisheries Jurisdiction in 1979 to control and rebuild the fishery • Expected a rise in Total Allowable Catch (TAC) by 1985 • Instead the fishery continued to decline and effectively closed in 1992

  10. What Happen? • Mismanagement? • Fishing mortality exceeded sustainable level estimates • Stocks never achieved 50% of predicted total allowable catch • Canadian fleet over harvested cod

  11. How? • Upper limit was used to calculate harvest quota every year • When upper limit became insufficient to economically support fishery quota was increased • Short term economic gain won out over biology

  12. The Irony • Biologists could see the catastrophe happening and were powerless to stop it • Long term economic loss (closure of fishery) far outweighs short term benefit • Economy loses more

  13. Now what? • How can we fish only to an extent which does not significantly alter it and the natural system in which it occurs? • Widely varying degrees of opinion.

  14. Problems • Estimating populations • Estimating catch • Predicting population change based on… • catch. • environmental statistics • limited knowledge of life history. • Tends to err on the side of over harvest • Doesn’t always consider ecology

  15. Some Solutions: • Marine Protected Areas • Effective if: • Large enough • Protect source populations • Effectively enforced • Currently well below 1% of marine systems are protected by MPA’s

  16. Legislation • Through regulation and laws control the total allowable catch • Effective regulation should be consistent with biology • International Compliance

  17. Responsible Recreation • Increasing evidence suggests impacts of recreational fishing

  18. Conclusions • Conservation of marine fisheries impacts peoples livelihoods, survival, and recreation. • It influences the marine and terrestrial environments. • It is everyone's responsibility.

  19. Case Study: The Impact of Overfishing***Please put all answers on looseleaf! • Vocab: list the definition of the following fishstock, net growth rate, MSY, TAC, OSY • Do case study but omit “l” and “m” • Do only question #2 from Questions for Application and Further Research

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