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Cait Nelson & Stephanie Avery-Gomm Oct 22 2010 Introduction Technological Advances of Fishing Fleets No Refugia = Can’t Run, Can’t Hide Resource Depletion Catch per Unit Effort Maintained Models are based on data that is imprecise and error prone Fishing Down; Removal of large long lived fish Food webs are altered, lack buffering capacity Reverse Trends; Reduction of Fleet, Increased Regs Solutions…Reduce Pressure on Fisheries Maximum Sustainable Yield management of single species stocks The largest yield (or catch) over an indefinite period At intermediate population densities individuals are able to breed to their maximum rate Surplus of individuals that can be harvested Growth rate of the population is at max due to the large number reproducing individuals Figure 1. Maximum sustainable yield occurs not at the maximum population level, but rather at a lower, optimal population level. Maximum Sustainable Yield Approach has been criticized as ignoring several key factors involved in fisheries management What might some of these key factors be? Fishing Down Marine Food Webs Mean TL of fished species declined from 1950- 1994 Gradual transition in landings from long-lived, high trophic level, piscivorous bottom fish toward short-lived, low trophic level invertebrates and planktivorous pelagic fish. Fishing down food webs leads at first to increasing catches, then to a phase transition associated with stagnating or declining catches. Fishing Down Marine Food Webs Fishing Down Marine Food Webs Discussion What effects might overexploitation of top trophic levels have on species and ecosystems? What other effects may FDMFW have? Other effects of FDMFW Trophic cascade examples What are the solutions to achieve sustainable fisheries? Solutions to achieve sustainable fisheries? Aquaculture Bridge the gap between supply and demand Reduce pressure on wild populations Aquaculture Discussion Why might aquaculture not help to reduce fishing pressure? Solutions to achieve sustainable fisheries? No take zones NTZ protect populations by creating reserves for sedentary species What other solutions exist? What other solutions exist? Marine Protected Areas Have been shown to have positive effects in rebuild depleted stocks of sedentary species. NTZ What other solutions exist? Consumer driven choices Consumer driven choices to avoid unsustainably fished stocks and endangered species Eg. Eco-labeling What other solutions exist? Consumer driven choices Ocean Wise simplifies eating seafood sustainably Towards Sustainability or Rebuilding Fisheries?
