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13. Nile Perch Population Dynamics in Lake Victoria :
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Ideal _hap_community- (hap_st and...
FIGURE 13.4
likely be close enough to shore to be threatened by them anyway . "Minimum size" determines the smallest size fish which may be caught by the gill
net and long line fisheries. This is equated to a change in minimum mesh
size. The reader is referred to (Schindler et al. 1998) for a discussion of the
effects of changing minimum legal size in this fishery.
The "ideal haplochromin e community" is a fraction (D- l) which determines the relative conservation focus of the management community. It
repr esents the percent dominance by haplochromines below which managers would consider raising the allowable total catch in order to reduce
predation pressures. A value of 1 will quickly eliminate perch from the fishery because managers will intensify fishing effort if the haplochromine
community consists of less then 100% of the prey base. A value of 0 will
eliminate fishing entirely.
The model calculates total biomass of Nile perch of legal size every day
(Figure 13.5). The percentage of that community that may be taken per day
by the fishery is then calculated in accordance to the difference between
the actual haplochromine community, and the ideal haplochromine commun ity. Thus, fishing intensity is regulated using haplochromines as indicator organisms.
13. Nile Perch Population Dynamics in Lake Victoria :
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Ideal _hap_community- (hap_st and...
FIGURE 13.4
likely be close enough to shore to be threatened by them anyway . "Minimum size" determines the smallest size fish which may be caught by the gill
net and long line fisheries. This is equated to a change in minimum mesh
size. The reader is referred to (Schindler et al. 1998) for a discussion of the
effects of changing minimum legal size in this fishery.
The "ideal haplochromin e community" is a fraction (D- l) which determines the relative conservation focus of the management community. It
repr esents the percent dominance by haplochromines below which managers would consider raising the allowable total catch in order to reduce
predation pressures. A value of 1 will quickly eliminate perch from the fishery because managers will intensify fishing effort if the haplochromine
community consists of less then 100% of the prey base. A value of 0 will
eliminate fishing entirely.
The model calculates total biomass of Nile perch of legal size every day
(Figure 13.5). The percentage of that community that may be taken per day
by the fishery is then calculated in accordance to the difference between
the actual haplochromine community, and the ideal haplochromine commun ity. Thus, fishing intensity is regulated using haplochromines as indicator organisms.