Sustainable Fishery Management / Fishery Stock Assessment

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Catch trends sometimes disagree to the fish population trends because fishery is not scientific survey but economic activity.
Fish population is not obvious as the number of trees on a mountain, because fish under water can not be seen directly.
Scientific assessment is important to know the fish population

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Sustainable Fishery Management / Fishery Stock Assessment

  1. 1. Fishery Stock Assessment Takashi Matsuishi At SERD, AIT, Thailand 24Feb-14Mar, 2014 1
  2. 2. Russell's Equation    YDGRBB tt 1 Biomassatt+1 Recruitment Growth NaturalMortality Yield Biomassatt
  3. 3. 3 Monitoring of Fish Population  Catch trends sometimes disagree to the fish population trends because fishery is not scientific survey but economic activity.  Fish population is not obvious as the number of trees on a mountain, because fish under water can not be seen directly.  Scientific assessment is important to know the fish population
  4. 4. 4 Population Estimation Methods
  5. 5. 5 Population Estimation Method  Direct Method  Sighting Counting (Line transect Method)  Acoustic Method (Echo sounder)  ScientificTrawl Survey  Mark & Recapture Method  Indirect Method  Depletion Method (DeLury Method)  Virtual Population Analysis(VPA)
  6. 6. 6 Examples of direct methods
  7. 7. 7 Line Transect Method  Data: distance from vessel, angle from course, survey line length  Output: search width, population density θ ℓ w w freq W N = n * A/2Wℓ
  8. 8. 8 Population Estimation of Mink Whale in Antarctic Sea Minke Whale Balaenoptera acutorostrata 1991 IWC Total: over 760 thousand
  9. 9. 9 Acoustic Method by using echo sounder
  10. 10. 10 Length(cm) Target Strength (dB/kg) Target strength
  11. 11. 11 Direct methods  Scientific and precise  Cruse by the research vessel is must  Very expensive to get data  Can not estimate population before starting scientific cruses.
  12. 12. 12 Examples of indirect methods
  13. 13. 13 Catch per unit effort(CPUE) Notation: C: Catch in Number N: Population in Number E: Fishing Effort q:Vulnerability C ∝ N (Effort=const.) C ∝ E (Population=cont.) → C = q N E → C / E = q N CPUE ∝ N
  14. 14. 14 DeLury Method  Data: Catch, Fishing Effort  Estimators: Population,Vulnerability  Assumption: CPUE ∝ Population Cumulative Catch CPUE 500 10 20
  15. 15. 15 Abalone Diving Fishery in Goto islands Cumulative Catch(t) CPUE(kg/d) ■ “Black” Abalone + “Red” Abalone
  16. 16. 16 Virtual Population Analysis Takashi Matsuishi Hokkaido Univ.
  17. 17. 17 VPA (Corhort Analysis)  An population estimation method from catch at age  by stock by year class  no need to use fishing information  Internationally most standard population estimation method  in International committees  forTotal Allowable catch  Theoretical development going on  ADAPT  SVPA  Length / weight basedVPA
  18. 18. 18 Age based model in population estimation papers 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% <50's 60s 70s 80s Megrey(1989)
  19. 19. 19 Standard VPA
  20. 20. 20 Virtual Population Analysis (VPA) Fishing Fishing Fishing Death Death Death Population at the beginning of age 2 Population at the beginning of age 3 Population at the beginning of age 4 Population at the beginning of age 5 1991 1992 1993 1994 1995 資源管理のABCより
  21. 21. 21 Basic equations 2, , 1 M F YA YA e e C N A   yAyA FF ,1,  2 ,1,1, M ya M yaya eCeNN   N: Population at age F: Fishing Mortality C: Catch at age M: Natural Mortality M N N F ya ya ya   1,1 , , ln
  22. 22. 22 N Year Age 1994 1995 1996 1997 1998 1 2 3 4 5 6+ given
  23. 23. 23 For Recent Year  If fishery is stable, selectivity, will be stable.  In this situation, F would be assumed as recent average value  3,12,11,1,1 3 1   yayayaya FFFF
  24. 24. 24 N Year Age 1994 1995 1996 1997 1998 1 2 3 4 5 6+
  25. 25. 25 An Example of Application
  26. 26. 26 TAC controlled stocks in Japan Species Stock Stock Assessment sardine Pacific Stock VPA Tuned by 6 AIs Tsushima WC Stock Egg number jack mackerel Pacific Stock VPA Tsushima WC Stock VPA Tuned by 2 AIs chub mackerel Pacific Stock VPA Tuned by 5 AIs Tsushima WC Stock VPA Tuned by 2 AIs southern mackerel Pacific Stock VPA East China Sea VPA Tuned by 2 AIs Pacific saury NW Pacific Stock Trawling Walleye Pollock North sea of Japan stock VPA Tuned Nemuro St. CPUE etc Southern Okhotsuku CPUE etc Pacific VPA Tuned by 2 AIs
  27. 27. 27 Walleye Pollock Pacific Stock  Habitat: Pacific coast of Northern Japan  Spawning Ground: Funka Bay  Migration: younger age inTohoku area, matured fish migrate to Doto area and spawinig fish in Funakabay area  Fishery:Trawl net(younger), Gillnet(older)  Age at mature: 3 years
  28. 28. 28 SSB - Recruitment Relationship 0 10 20 30 40 50 60 70 0 5 10 15 20 25 30 35 40 45 50 Recruitment(Age0,100million) Spawing Stock Biomass(10,000t)
  29. 29. 29 VPA  ADAPTVPA  Tuned by Acoustic Survey and CPUE of trawl fishery           145lnln 7lnln 2 ,, 2 ,1,1     y yaya y yy bNX qNISSQ
  30. 30. 30 0 5 10 15 20 25 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 百 万 0歳 1歳 2歳 3歳 4歳 5歳 6歳 7歳 8+歳 Difference between Tuned or not Without Tuning Tuned 0 5 10 15 20 25 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 百 万 0歳 1歳 2歳 3歳 4歳 5歳 6歳 7歳 8+歳 millionmillion Age
  31. 31. 31 Limitation and Potentials
  32. 32. 32 Limitations of VPA  Low reliability from little information  Can not apply automatically  Natural mortality and catch at age are must  Difficult to use short lived sp.  Use only for separate stock
  33. 33. 33 Potentials of VPA  Most reliable now  Utilize maximum informations  Flexible (eq. age dependence of M)  Possibility for estimating M by using separableVPA  Flexibly incorporate other informations (IntegratedVPA)  Know limitation and Use widely
  34. 34. 34 Perspective for the Future Stock Assessment
  35. 35. 35 Perspective for the Future Stock Assessment  Direct method for estimating recent population and Indirect method for estimating productivity of the stock  Combination of various data available to use more information to the population estimation  Simulation study for examining the validation of the method  Age-based model for the precise assessment and length- or weight-based model for quick assessment, especially for tropical fish

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