Bergen extinction - Extinction of fish stocks Peter Berck...

Info iconThis preview shows pages 1–18. Sign up to view the full content.

View Full Document Right Arrow Icon
  Extinction of fish stocks  Peter Berck Professor University of California, Berkeley Visiting Professor, Umeå Universitet
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Marine Resource Destruction We take it as given that policy should avoid causing very low populations of marine organisms. The two major ways of reducing numbers of fish are Overfishing Habitat destruction
Background image of page 2
  Sturgeon
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Overfishing (NYT) WASHINGTON, Sept. 30 [2005]- The United States Fish and Wildlife Service will begin banning imports of beluga caviar and other beluga products from the Caspian Sea on Friday, after caviar-exporting countries in the region failed to provide details of their plans to conserve the fish, which is listed internationally as a species threatened with extinction.
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Atlantic Cod Catch (Metric Tons) 1950 24.5 1976 25 1982 52.8 2003 10.7
Background image of page 6
  Sebastes sp . caught north of Fanny Shoals, CA, 300 ft.  depth. Photo: R.D. Sage  
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Rockfish In September 2002, West Coast fisherman faced the new reality when they learned that severe restrictions would be placed on bottom fishing on much of the continental shelf from Canada to Mexico. The Pacific Fishery Management Council implemented the strictest regulations in the history of West Coast fishing in a final-hour attempt to save the rockfish. -Pew Ocean trust p. 36
Background image of page 8
  Rules to Manage and Protect  Biological Rules MSY Rules to regulate spawners/recruit and such Frank assessment of minimum viable stock size Economic rules Catch fish at the profit(or summed surplus) maximixing rate
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Why Don’t the Rules Protect
Background image of page 10
  Life Without Rules:  Open Access Model 0 500 1000 1500 2000 2500 3000 0 200000 400000 600000 800000 Harvest metric tons Stock (1000) metric tons North Sea Herring 1963-77; Bjorndal and Conrad
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  The Model dx/dt =f(x) – s q x is stock s is number of boats q is catch per boat f is growth function with usual logistic like shape
Background image of page 12
  entry ds/dt = pq – c(q,x) – fc p is price c is variable cost function given x fc is fixed costs per unit time
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Catch per boat p = dc/ dq Price equal marginal cost
Background image of page 14
  Specific cost function C(q,x) = T(x-x*) c(q) c(q) = q K T = (x-x*) -R Supply per boat p = T c’ = TKq K-1 q = (p/TK) (1/(K-1)) For the moment we assume that x*=0.
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
  Phase space We graph this system in the x-s phase space ds/dt = 0 is a vertical line because s appears nowhere on the right hand side of the ds/dt equation.
Background image of page 16
  Two possibilities for dx/dt = 0 s = f(x)/q on dx/dt = 0. When x is large enough f(x) is zero, call this x max. So x= x
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 18
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 70

Bergen extinction - Extinction of fish stocks Peter Berck...

This preview shows document pages 1 - 18. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online