1 / 24

Food and Agriculture Organization of the United Nations

Food and Agriculture Organization of the United Nations. Stock Assessment & the Long-term Sustainability of Fishery Resources Yimin Ye Senior Fishery Resources Officer. www.fao.org. Outline. Fish population dynamics Stock assessment and its role in fishery management

alexia
Download Presentation

Food and Agriculture Organization of the United Nations

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. Food and Agriculture Organization of the United Nations Stock Assessment & the Long-term Sustainability of Fishery Resources Yimin Ye Senior Fishery Resources Officer www.fao.org

  2. Outline • Fish population dynamics • Stock assessment and its role in fishery management • Assessment models and data requirements • Sustainability of fish stocks • An example of regional fisheries in developing countries www.fao.org

  3. Recruitment Natural death Fish stock Individual growth Fishing removal Fish Stock and Its Variation in Abundance www.fao.org

  4. WhatIs Stock Assessment? ΔB-variation in biomass R-recruitment G-growth M-natural death F-fishing removal • Fish stock Stock assessment is to evaluate the various components of the stock equation www.fao.org

  5. What Can Stock Assessment Tell Us? • What is in the resource envelope? • how much fish is available, • what is the potential productivity • distribution • population structure • How much is being harvested using which type of gears • To predict consequences of different harvest strategies • To provide advice on policy formulation and management plans for the long-term sustainability of the fishery www.fao.org

  6. Basic Elements of a Fishery • The standing stock (biomass) • The input (fishing effort) • The output (catch) • The processes that link input and output • Biological processes • Fishing operations www.fao.org

  7. Control Measures and Fishing Capacity Input Standing Stock & Processes Output No. of vessels Vessel size Fishing time Minimum size Meash size Gear type TAC Bag limit Bycatch limit Fishing Capacity Overcapacity vs Over-exploitation FAO (1999), Arrizabalaga et al. (2009) www.fao.org

  8. Management of Fishing Capacity • Code of Conduct (7.1.8): “States should take measures to prevent or eliminate excessfishing capacity and should ensure that levels of fishing effort are commensurate with the sustainable use of fishery resources” • International Plan of Action for the Management of Fishing Capacity (FAO 1999) • “States and RFOs confronted with an overcapacity problem, where capacity is undermining achievement of long-term sustainability outcomes, should endeavour initially to limit at present level and progressively reduce the fishing capacity applied to affected fisheries. • Three phases of implementations: assessment and diagnosis, adoption of management measures, and periodic adjustment of such assessment and measures”. www.fao.org

  9. Assessment of Fishing Fleet Capacity • Peak to peak method (Kirkly & Squires 1999) • Stochastic frontier (Battese & Coelli 1993) • Data envelopment analysis (DEA, Reid & Squires 2007) Assessment of fishing capacity is difficult & data-demanding, eg. DEA requires trip-by-trip info on catches, fishing effort and vessel characteristics. www.fao.org

  10. The Role of Stock Assessment in Fishery Management Fishing activity Data collection Stock Assess. Advice (SAG) Regulations Policy Formulation (SAC) Fish stock www.fao.org

  11. Yield/recruit analysis Biomass-based models Low Simple Age-structured models Length-based models Ecosystem models High Complex Data Requirements of Various Models Model Formulation Data Requirements www.fao.org

  12. Types of Data Used in Stock Assessment Vessel Stock assessment Gear Scientific survey data Catch Life history parameters Fishery dependent data Soci-economic data www.fao.org

  13. What Models to Use? • Data availability e.g. age composition data • Characteristics of the fishery e.g. spawner-recruit relationship may not be clear for short-lived species • What you want to know e.g. the consequence of capturing juveniles www.fao.org

  14. Fishery Management Objectives • Over-arching objective • Maintain stocks at the level capable of producing MSY • Modified by other factors, eg economic, employment, conservation • Precautionary approach (uncertainties in data, models and implementation) • Objective varies with users/countries www.fao.org

  15. Examples: Different Management Objectives MEY MSY Jobs Ecosystem preservation www.fao.org

  16. Sustainability of Fish Stocks • The meaning of sustainability varies with management objectives (BMSY, BMEY, etc) • Maintain stocks at the level capable of producing MSY (UNCLOS 1982, UN Code of Conduct 1995, UN Fish Stock Agreement 1995, UNEP & WWF 2007) www.fao.org

  17. Natural ecosystem Target species Fish community Habitat Manag. system Policy Harvest strategy Research Controller Foundation Human system Fishers & vessels Comsumers Technology Soci-economic environ. Drive Three Pillars of a Fishery System www.fao.org

  18. Sustainability Criteria Foundation Controller Natural ecosystem Target species Fish community Habitat Manag. system Policy Harvest strategy Research 3. ? 1.Stock>BMSY Human system Fishers & vessels Comsumers Technology Soci-economic environ. Drive 2.Capacity output<MSY (FAO 1998, Arrizabalaga et al. 2009) www.fao.org

  19. Data Availability in Developing Countries Yield per recruit analysis Vessel Length-converted catch curve models Gear Scientific survey data Catch Life history parameters Fishery dependent data Soci-economic data www.fao.org

  20. An Example: Kingfish in the Arabian Sea, Oman Sea & Arabian Gulf Grandcourt et al 2005 FACTS • Largest fishery in the GCC • Migratory shared stock • No info on distr. & migr. route • Only catch data available • No info on fishers, vessels & fishing effort • No regulations in place Max Y/R • Catch dropped to 1/3 • 65% of caught fish immature • A minimum size of 84 CM increasing catch by 7000 t • Closure of Aug-Sept • A minimum legal size of 65 CM www.fao.org

  21. Sustainability Criteria for Data Poor Fisheries Controller Foundation Natural ecosystem Target species Fish community Habitat Manag. system Policy Harvest strategy Research 3.? 1.Indicators? Human system Fishers & vessels Comsumers Technology Soci-economic environ. 2.Fishing capacity? Indicators (vessel tonnage & engine power) Drive www.fao.org

  22. Indicators of Stock Abundance for Fishery Management Purposes • Landings < 50% of the peak-5 years’ average without a clear cut in effort • Abundance indices < 50% of the initial values (catch rates of commercial or research vessels) • Fishing mortality >natural mortality (length-based methods) • The use of indicators involves a great uncertainty • Such uncertainties can be dealt with by adaptive approaches for management purposes, but using indicators to determine sustainability is much more difficult as it requires a clear Reference Value www.fao.org

  23. FAO’s Technical Assistance to Developing Countries • Technical Guidelines • Stock assessment software • Workshops at national and regional levels • Technical cooperation projects • Direct contact with FAO staff www.fao.org

  24. Thanks www.fao.org

More Related