. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. V â 'â â¢â¢.. / I I I I I I I I I I I I I I L 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 SEASON FIGURE 8. Growth of 1-year-old shrimp by month during the fishing seasons and the mean June weight by year. MANAGEMENT IMPLICATIONS It should be clear that if environmental conditions have a strong influ- ence on shrimp productivity, any density dependent relationships will be quite difficult to discover. Because the General
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. V â 'â â¢â¢.. / I I I I I I I I I I I I I I L 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 SEASON FIGURE 8. Growth of 1-year-old shrimp by month during the fishing seasons and the mean June weight by year. MANAGEMENT IMPLICATIONS It should be clear that if environmental conditions have a strong influ- ence on shrimp productivity, any density dependent relationships will be quite difficult to discover. Because the General Production model treats environmental conditions as constant, any relationship defined by this model will be of limited value in managing shrimp because the environ- mental effects will not be included. Thus, in periods of favorable environ- mental conditions, more biomass will be available than will be computed by the model. The converse will be true under poor environmental condi- tions. In this situation a constant quota based on the model will not pre- vent overfishing but will limit the fishery when a surplus is available. One consequence of not being able to define a relationship between production and population size is that we are left without a reliable method of establishing annual quotas. Hovv'ever, quotas were initially es- tablished for the shrimp areas to protect the resource from over harvest- ing and thus insure an adequate spawning stock. Later, when the Schaefer model was applied to the fishery and an equilibrium yield calculated, the quota was intended to insure annual yields approaching the theoretical maximum equilibrium yield. With the additional data now available, the use of the quota for the latter reason is unrealistic. Because age I females have been the major component of the spawning stock, we can insure an adequate spawning stock by providing protection to the age I shrimp. In recent years, a greater number of shrimp in every year class hav
Size: 1763px × 1417px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcaliforniadeptoffishandgame, bookauthorcaliforniafish
