Georges Bank East Scotian Shelf Grand Banks Type of OrganismsExamples GroundfishCod, Haddock, Hake Pelagic FishSardine, Anchovy, Herring, Mackerel, Tuna CrustaceansCrab, Lobster, Shrimp, Krill MolluscsOysters, Mussels, Clams. Squid, Scallops Stern trawler fishing: After sonar on the trawler finds the fish, theyre captured by a trawl net more than 122 meters (400 feet) wide. The largest nets extend about 0.8 kilometer behind the towing vessel and are large enough to hold a dozen 747 jetliners. 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. Todays Fisheries Are Not Sustainable Maximum sustainable yield maximum amount of any species that can be harvested without affecting future yields Overfished status assigned to fish stocks that have been harvested so there is not enough breeding stock left for replenishment Commercial extinction depletion of a species to the point where it is no longer profitable to harvest By Catch animals unintentionally killed when other species are being harvested 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. Over - Whaling continues Much more complicated than reduction of one species Trophic interactions Examples: Salmon, killer whale, sea otter Change in ecosystem structure Loss of biodiversity By-catch is all non-target species caught with target species whether retained then sold or discarded Example: Dolphins caught in tuna nets. Often a problem with widespread use of unselective fishing gear Bottom trawling disturbs everything on the ocean floor! 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 (should err on side of caution Cautionary Principle) Doesnt always consider ecology Gulf of Maine fishermen face 6-month cod ban Regulation and laws control the total allowable catch (TAC) Effective regulation should be consistent with biology; scientist recommendations should be taken into account. International Compliance Conservation of marine fisheries impacts peoples livelihoods, survival, and recreation. Influences the marine and terrestrial environments. It is everyone's responsibility!!