L11. Marine Resources - MarineResources n Current Problems...

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Marine Resources n Current Problems in Marine Fisheries q Overfishing – substantially diminished stocks q Overcapitalization in fishing fleets q Water pollution q Transboundary conflicts in fishing rights n This class will deal with overfishing and overcapitalization q Both largely the result of open-access
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Myers and Worm – Analysis of Fishing  Data (from CBC.CA, May 15th 2003) n Big fish disappearing from oceans: The world's oceans have lost 90 per cent of prized tuna, swordfish and marlin since industrialized fishing began q Analysis of nearly 50 years of data on predatory fish catches worldwide. n Found that it generally takes less than 15 years for commercial fishing operations to reduce the resource base to less than 10 per cent. n To measure the decline in open oceans, the researchers used data from Japanese longline catches, massive nets with thousands of hooks stretched across the ocean to catch everything in their path. q After the Second World War, longlines used to catch 10 fish per 100 hooks. Now they're lucky to catch one. n Daniel Pauly of the University of British Columbia: when fishing went bad in one area, vessels simply moved on to scour another n Similar to a 1994 estimate by the UN Food and Agriculture Organization: almost 70 per cent of marines stocks were overfished or fully exploited n Ransom Myers & Boris Worm are Fisheries Biologists at Dalhousie
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Modeling a Fishery n Simple Bio-economic Model q Biology of fishery growth combined with economic consequences q Biomass: total size of fish stock n Depends on q Predator and prey, fecundity, water currents, food supply etc. n Growth comprises of q Increase in number of fish q Increase in size of individual fish n Food supply can usually support a fixed biomass size – carrying capacity q Logistic Growth Curve – also a sustained yield curve Stock Growth Increment y* s*
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The Logistic Growth Curve n Inverted U shaped n Annual increment with small population is small n Reaches max at 1400 n Drops to zero at 2600 n 1400 is stock that gives Maximum Sustainable Yield n 2600 is ?? n Logistic Model first proposed by P. F Verhulst (1938) Number of Pheasants 1400 2600 Annual Increment in Number of Pheasants Logistic Growth Curve
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n Look at growth increment function q What is carrying capacity? q
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This note was uploaded on 11/18/2011 for the course ECON 374 taught by Professor Sumeetgulati during the Winter '11 term at The University of British Columbia.

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L11. Marine Resources - MarineResources n Current Problems...

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