1 / 23

Artificial Population Regulation

This overview discusses artificial population regulation, highlighting its importance for managing fisheries and ensuring the sustainability of species. It emphasizes the concept of Maximum Sustained Yield (MSY), expressed through the logistic equation, and its role in defining optimal harvest levels. The definition of MSY as per the U.S. Fishery Conservation and Management Act considers ecological, social, and economic factors. Additionally, it explores fixed quota harvesting, population viability analysis, and the challenges related to changing environmental conditions.

paki-beasley
Télécharger la présentation

Artificial Population Regulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Artificial Population Regulation • For regulation of populations • For commercial harvest • Maximum Sustained Yield (MSY) • Based on the logistic equation: • dN/dt = rN((K-N)/K) • Generally found at 1/2 the carrying capacity (K) • Formula for MSY • 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 • 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 45o line is density independent replacement level r populations K type populations

  8. Whale harvests Note the lack of whaling during WWII

  9. Efficiency of whale harvest after WWII

  10. Haddock & Cod fisheries

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

  12. Fixed effort harvesting

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

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

  15. Dynamic pool

  16. Dynamic pool example • Plaice (Krebs, Fig. 17.5) • 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 • Population viability analysis (PVA) • How vulnerable to extinction? Includes minimum viable population (MVP) • Three general methods • Long term studies - biogeographical patterns • Subjective expert assessment • General mathematical model • Simulation models seem to hold the most promise • Problems with the analysis: • Changing conditions • Stochastic forces

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

  21. Florida panther

  22. Management decisions Sumatran Rhino

More Related