1. Artificial Population Regulation n For regulation of populations n For commercial harvest n Maximum Sustained Yield (MSY) – Based on the logistic equation: n dN/dt = rN((K-N)/K) – Generally found at 1/2 the carrying capacity (K) – Formula for MSY n H = (Kr)/4

2. Frequency of Harvest The most frequent harvests can be taken at intermediate population sizes.

3. Maximum sustainable yield (MSY) Anchovy MSY Krebs: Fig. 17.3

4. Anchovy Harvest Record

5. Optimum yield Below MSY because of other interests n Defined in the U.S. Fishery Conservation and Management Act of 1976 – “the quantity... (1) that will provide the greatest overall benefit to the nation, with reference to food production and recreation and – (2) that is prescribed as such on the basis of maximum sustained yield as modified by any relevant economic, social, or ecological factors.

6. Fixed Quota Harvesting

7. Reproduction curves & replacement K type populations r populations 45 o line is density independent replacement level

8. Whale harvests Note the lack of whaling during WWII

9. Efficiency of whale harvest after WWII

10. Haddock & Cod fisheries

11. Predictions n Garrod & Jones (1974) n Cod fishery n Ignored by fisheries managers

12. Fixed effort harvesting

13. Multiple equilibria in harvesting E o would harvest to extinction U= unstable equilibrium Declining harvest efficiency with increased density

14. IFQ’s n Individual fishing quota – Allowable catch divided into %’s awarded to or purchased by fisherman and companies n Avoids “fishing derby” n Can be sold or traded n High cost excludes many fishermen – Can be overcome if community quotas are allowed

15. Dynamic pool

16. Dynamic pool example n Plaice (Krebs, Fig. 17.5) n Best harvest rate would have been about 1/2 of actual level

17. Interface with economics ? + - + + + + - - + + + + - - + + - - + + + +

18. Cycle Catch Effort Price Includes political pressure to increase effort

19. Biological Conservation n Population viability analysis (PVA) – How vulnerable to extinction? Includes minimum viable population (MVP) n Three general methods – Long term studies - biogeographical patterns – Subjective expert assessment – General mathematical model n Simulation models seem to hold the most promise n Problems with the analysis: – Changing conditions – Stochastic forces

20. Causes of rarity n Habitable areas are: – Short-lived – Small – Isolated n Resources sparse n Predators n Genetic variation lacking

22. Florida panther Input demographic patternsSimulation results Initiation Probability of extinction (years) Age of reproduction Adult mortality Litter size NK 2550100200 Mean time to extinction 3253.045 0.240.771.00 39 3252.545 0.380.941.00 30 3203.045 0.040.280.95 77 3202.545 0.110.571.00 51 2253.045 0.040.450.77 96 2252.545 0.110.910.99 56 2203.045 0.000.040.11 114 2202.545 0.010.270.56 107

23. Management decisions Sumatran Rhino