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Fishing theory,Principle of Fishing

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PRINCIPLE 1: Sustainable fish stock A fishery must be conducted in a manner that does not lead to over-fishing or depletion of the exploited populations and, for those populations that are depleted, the fishery must be conducted in a manner that demonstrably leads to their recovery PRINCIPLE 2: Minimizing environmental effect Fishing operations should allow for the maintenance of the structure, productivity, function and diversity of the ecosystem (including habitat and associated dependent and ecologically related species) on which the fishery depends.

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Fishing Technology
Principle of fishing PRINCIPLE 1: Sustainable fish stock A fishery must be conducted in a manner that does not lead to over-fishing or depletion of the exploited populations and, for those populations that are depleted, the fishery must be conducted in a manner that demonstrably leads to their recovery PRINCIPLE 2: Minimizing environmental effect Fishing operations should allow for the maintenance of the structure, productivity, function and diversity of the ecosystem (including habitat and associated dependent and ecologically related species) on which the fishery depends.
PRINCIPLE 3: Effective management The fishery is subject to an effective management system that respects local, national and international laws and standards and incorporates institutional and operational frameworks that require use of the resource to be responsible and sustainable.
Criteria for fishing • it can be continued indefinitely at a reasonable level; • it maintains and seeks to maximize, ecological health and abundance, • it maintains the diversity, structure and function of the ecosystem on which it depends as well as the quality of its habitat, minimizing the adverse effects that it causes; • it is managed and operated in a responsible manner, in conformity with local, national and international laws and regulations; • it maintains present and future economic and social options and benefits; • it is conducted in a socially and economically fair and responsible manner.
Why this principle of fishing? • Appropriate fishing gear should be used • Fishing crafts should only be used when it is necessary • To maintain sustainable fish harvesting • To have a good catch avoiding over fishing • To maintain minimum effort and maximum catch • To select/find out new fishing ground • Fishing during a definite season and ban on spawning season • To maintain a balance between the number of fish caught and the number of young fish entering into the population • Less wastes during fishing
Fishing theory,Principle of Fishing
Shark fin
Theory of fishing • Fishing is a complex problem for the fishery scientist • A given population or community should be exploited and the fishing activity should be adjusted to obtain the best results • The best results point to the maximum sustainable yield • That is the way to consume fish year to year without depleting the fish stock The different methods to solve this problem are: 1. Empirical method 2. Analytical method
Empirical method • This method considers the maximum sustainable yield • This method takes in account by the yield and the fishing effort The fishing effort is measured by: -the number and size of fishing gears and crafts -the amount of time spent in fishing and yield Criticisms: -it provides no means of judging the condition of getting MSY -this condition may not give the best yield in future -in some cases the population couldn’t be exploited to give the better result
Analytical method: • This method investigate the cause of change in population size and yield • It also investigates the cause of fish mortality due to predation, diseases, salinity, etc. • The criticism of empirical method can be solved by this method
Theoretical model: The following parameters are need to be studied to obtain MSY: i) Recruitment (R): the number of a single year group entering the exploitable phase of a stock in a given period by growth of smaller individuals ii) Growth (G): increase in size (length and weight). Fish growth curve is S shaped. iii)Natural Mortality (M): mortality due to predation, diseases, salinity, etc iv)Fishing Mortality (F): mortality by fishing
Formula: For over fishing, R+G-M<F For under fishing, R+G-M>F For optimum fishing, R+G-M=F
Maximum Sustainable Yield (MSY) • MSY is such amount of fish stock which are caught from a certain area without causing any harm • MSY is such amount of fish stock which are captured from a certain water body without depleting or hampering the actual stock • By increasing fishing effort, total catch will be increased but at a position of increasing fishing effort, total catch will be maximum and after that total catch will be decreased by increasing fishing effort. In case of MSY, R+G=M+F

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Fishing theory,Principle of Fishing

  • 2. Principle of fishing PRINCIPLE 1: Sustainable fish stock A fishery must be conducted in a manner that does not lead to over-fishing or depletion of the exploited populations and, for those populations that are depleted, the fishery must be conducted in a manner that demonstrably leads to their recovery PRINCIPLE 2: Minimizing environmental effect Fishing operations should allow for the maintenance of the structure, productivity, function and diversity of the ecosystem (including habitat and associated dependent and ecologically related species) on which the fishery depends.
  • 3. PRINCIPLE 3: Effective management The fishery is subject to an effective management system that respects local, national and international laws and standards and incorporates institutional and operational frameworks that require use of the resource to be responsible and sustainable.
  • 4. Criteria for fishing • it can be continued indefinitely at a reasonable level; • it maintains and seeks to maximize, ecological health and abundance, • it maintains the diversity, structure and function of the ecosystem on which it depends as well as the quality of its habitat, minimizing the adverse effects that it causes; • it is managed and operated in a responsible manner, in conformity with local, national and international laws and regulations; • it maintains present and future economic and social options and benefits; • it is conducted in a socially and economically fair and responsible manner.
  • 5. Why this principle of fishing? • Appropriate fishing gear should be used • Fishing crafts should only be used when it is necessary • To maintain sustainable fish harvesting • To have a good catch avoiding over fishing • To maintain minimum effort and maximum catch • To select/find out new fishing ground • Fishing during a definite season and ban on spawning season • To maintain a balance between the number of fish caught and the number of young fish entering into the population • Less wastes during fishing
  • 8. Theory of fishing • Fishing is a complex problem for the fishery scientist • A given population or community should be exploited and the fishing activity should be adjusted to obtain the best results • The best results point to the maximum sustainable yield • That is the way to consume fish year to year without depleting the fish stock The different methods to solve this problem are: 1. Empirical method 2. Analytical method
  • 9. Empirical method • This method considers the maximum sustainable yield • This method takes in account by the yield and the fishing effort The fishing effort is measured by: -the number and size of fishing gears and crafts -the amount of time spent in fishing and yield Criticisms: -it provides no means of judging the condition of getting MSY -this condition may not give the best yield in future -in some cases the population couldn’t be exploited to give the better result
  • 10. Analytical method: • This method investigate the cause of change in population size and yield • It also investigates the cause of fish mortality due to predation, diseases, salinity, etc. • The criticism of empirical method can be solved by this method
  • 11. Theoretical model: The following parameters are need to be studied to obtain MSY: i) Recruitment (R): the number of a single year group entering the exploitable phase of a stock in a given period by growth of smaller individuals ii) Growth (G): increase in size (length and weight). Fish growth curve is S shaped. iii)Natural Mortality (M): mortality due to predation, diseases, salinity, etc iv)Fishing Mortality (F): mortality by fishing
  • 12. Formula: For over fishing, R+G-M<F For under fishing, R+G-M>F For optimum fishing, R+G-M=F
  • 13. Maximum Sustainable Yield (MSY) • MSY is such amount of fish stock which are caught from a certain area without causing any harm • MSY is such amount of fish stock which are captured from a certain water body without depleting or hampering the actual stock • By increasing fishing effort, total catch will be increased but at a position of increasing fishing effort, total catch will be maximum and after that total catch will be decreased by increasing fishing effort. In case of MSY, R+G=M+F