(6.8)
The following table presents the annual total catches (in tons) and the corresponding catches by fishing unit effort (kg/fishing day of the fleet PESCRUL) of the stock of Deepwater rose shrimp, Parapenaeus longirostris, of the Algarve during the period 1983 to 1994 (Mattos Silva, 1995).
Year |
Y (t) |
cpue |
1983 |
538 |
235 |
1984 |
638 |
131 |
1985 |
431 |
63 |
1986 |
99 |
22 |
1987 |
37 |
8 |
1988 |
62 |
21 |
1989 |
437 |
77 |
1990 |
146 |
28 |
1991 |
126 |
26 |
1992 |
53 |
25 |
1993 |
91 |
41 |
1994 |
232 |
66 |
Using the following parameters of the integrated Fox model and Yoshimoto & Clarke (1993):
k = 1580 t, q = 0.39 thousand days^{-1} and r = 0.55 year^{-1}:
1. Project the cpue and the catch in weight for the year 1995, supposing that the fishing effort will be maintained equal to that of 1994 (situation status quo).
2. Determine the target reference points, Y_{MSY}, MSY and F_{MSY} and the indices MSY and f_{MSY}.
3. Determine the target reference points, Y_{0.1}, 0.1 and F_{0.1} and the indices ¯U_{0.1} and f_{0.1}.
4. Determine the percentages of the carrying capacity corresponding to the target points F_{MSY} and F_{0.1}
5. Based on the results obtained in the previous questions, make your comments on the state of the stock and of its exploitation.
6. Suppose that one intends to reduce the fishing effort in 1995 by about 20 percent relative to the effort of 1994. Project the catch in weight for 1995 and present the variations resulting from that effort reduction on the catch in weight and on the biomass.