1. 26-28 May 2009Dr. Mala Supongpan Unusable Stock Recruitment Growth Natural Deaths Disease Emigration Immigration Recruitment Usable Stock Growth Natural Deaths Disease Emigration Immigration Yields Dynamics of fish stock Fishing mortality=F

2. 26-28 May 2009Dr. Mala Supongpan R = Recruitment G = Growth M =Natural mortality F = Fishing mortality Can be controlled? HOW?

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5. 26-28 May 2009Dr. Mala Supongpan Yield against effort CPUE against effort Holistic methods Analytical methods

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7. 26-28 May 2009Dr. Mala Supongpan  Catches, Species and Sizes composition  Abundance  Biomass estimation  Analytical methods and Holistic methods  Parameter estimation (recruitment, growth, mortality-natural mortality, fishing mortality and total mortality)  Catch and effort data from statistic record (time series)  Population size and catchability  Using catch per unit effort to find original population size and catchability The fish stock assessment needs:

8. 26-28 May 2009 Dr. Mala Supongpan Parameters for fish stock assessment 1. Length-weight 2. Growth parameter 3. Mortality And data on production Catch and effort, production and biomass

9. 26-28 May 2009Dr. Mala Supongpan Modal Progression Analysis

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12. 26-28 May 2009Dr. Mala Supongpan 1. Estimation of initial population size and catchability coefficient from the fishing success to catch or effort Original population size catchability For virgin stock or limited data Leslie’s method DeLury’s method Cumulative catch+ Cumulative effort+ Z=M+F Z=M+qf F=qf (Roughly virgin stock size)

13. 26-28 May 2009Dr. Mala Supongpan 2. Estimation of Z using CPUE data 3. Natural mortality estimation When no fishing 4. Fishing mortality estimation F=Z-M

14. 26-28 May 2009Dr. Mala Supongpan Estimation of total mortality (Z) 1. CPUE data 2. Catch curve based on length composition data 3. Cumulative catch curve based on length composition data 4. Beverton and Holt’s Z equation 5. Plot Z on effort 1. Estimate Z from CPUE data From above equations, then gives: *

15. 26-28 May 2009Dr. Mala Supongpan Plot Z against effort to estimate F and M Z = M + q*fF = Z - M

16. 26-28 May 2009Dr. Mala Supongpan B = CPUE * A /a*X 1 B = Biomass (tons/ km 2 ) A = total area (km 2 ) (101,384 km 2) a = Swept Area = D*h*X 2 { D= (V*t) = 2.5*1} h ( head rope) (= 39 m) X 2 = 0.5 a = (2.5*1.852) * (0.039*0.5) = 0.090285 X 1 = 0.5 X 2 = 0.5 Biomass estimation

17. 26-28 May 2009Dr. Mala Supongpan Swept area to estimate biomass

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19. 26-28 May 2009Dr. Mala Supongpan Survey strata by depth

20. 26-28 May 2009Dr. Mala Supongpan Sustainable yield estimation Virgin biomass For conservation, a- should be=0.3 ZB = (F+M)B and the catch Y = FB

21. 26-28 May 2009Dr. Mala Supongpan Definition Catchability ( ): A fraction of a fish stock which is caught by a defined unit of the fishing effort. When the unit is small enough that it catches only a small part of the stock-0.01 or less-it can be used As an instantaneous rate in computating population change. Also called catchability coeffifient.

22. 26-28 May 2009Dr. Mala Supongpan Availability: The fraction of a fish population which lives in regions where it is susceptible to fishing during a given fishing season. This fraction receives recruits from or become mingled with the non-available part of the stock at other seasons, or in other years.

23. 26-28 May 2009Dr. Mala Supongpan Catch per unit of effort (CPUE): The catch of fish, in number or in weight, taken by a defined unit of fishing effort. Also called Catch per effort, fishing success, availability.

24. 26-28 May 2009Dr. Mala Supongpan Biomass: The weight of a fish stock, or of some defined portion of it. Fishing effort: The total fishing gear in use for a specified period of time. When two or more kinds of gear are used, they must be adjusted to some standard type.

25. 26-28 May 2009Dr. Mala Supongpan References Gulland, J.A. 1983. Fish stock assessment. (FAO/Wiley series on food and agriculture; v. 1), 223 pp. Ricker, W.E. 1975. Computation and interpretation of biological statistics of fish populations, pp.151-155.

26. 26-28 May 2009Dr. Mala Supongpan Exercises 1 and 2