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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 – Mammals- whales 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. 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. 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. 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. 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 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 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 What Happen? • Mismanagement? – Fishing mortality exceeded sustainable level estimates – Stocks never achieved 50% of predicted total allowable catch – Canadian fleet over harvested cod 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 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 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. 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 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 Legislation • Through regulation and laws control the total allowable catch • Effective regulation should be consistent with biology • International Compliance Responsible Recreation • Increasing evidence suggests impacts of recreational fishing Conclusions • Conservation of marine fisheries impacts peoples livelihoods, survival, and recreation. • It influences the marine and terrestrial environments. • It is everyone's responsibility. 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