10.1 M. merluccius
10.2 Merluccius spp.
10.3 Conclusions
The effect of fishing has been investigated by:
(a) constructing theoretical curves of the relationship between yield per recruit and the rate of mortality due to fishing. These curves have been used to determine the level of fishing mortality (Fmax) for which the yield per recruit is a maximum; andSince the exact values of the parameters are not known, different sets were used, covering the probable range. The results are given in Tables 8-11. The curves corresponding to the best estimates are given in Figures 6-9.(b) determining the current value of fishing mortality to see how this compares with Fmax.
Table 8 and Figure 6 show the theoretical relationship between yield per recruit and fishing mortality rate for this species at the current age of first capture. Fmax is about equal to 0.12, and is not much affected by differences in the parameters.
From an analysis of the length composition of the catch, the current value of fishing mortality is 0.5, a value considerably greater than Fmax.
Table 10 and Figure 8 show the theoretical relationship between yield per recruit and fishing mortality at the current age of first capture. For the best estimates of the parameters Fmax is about 0.6. The current value of F is about 0.7, a value somewhat greater than this estimate of Fmax.
For both species, the analysis shows that it should be possible to increase the sustainable yield per recruit by reducing fishing effort (and hence fishing mortality). Theoretically, the reduction in fishing mortality needed to maximize the yield per recruit is -76 percent for M. merluccius and -13 percent for Merluccius spp. For M. merluccius a reduction in effort should lead to relatively large gains in yield per recruit. For Merluccius spp. the theoretical gain from reducing fishing mortality to the optimum value should be relatively small.
