(6.7.1)
The following table presents the annual total catch Y, (t) and
mean biomass 
, (t) for the
fishery of the Iberic stock (Div. VIIIc and IXa) of sardine, Sardina
pilchardus, between 1977 and 1996, used by the Working Group of ICES (ICES,
1998a).
|
Year |
Y (t) |
|
|
1977 |
125750 |
750289 |
|
1978 |
139990 |
759192 |
|
1979 |
153441 |
763313 |
|
1980 |
191682 |
804765 |
|
1981 |
214133 |
842091 |
|
1982 |
204504 |
802573 |
|
1983 |
181139 |
713376 |
|
1984 |
202686 |
794856 |
|
1985 |
204107 |
810539 |
|
1986 |
180606 |
679808 |
|
1987 |
168825 |
547179 |
|
1988 |
158540 |
481295 |
|
1989 |
137126 |
431719 |
|
1990 |
139157 |
368099 |
|
1991 |
127756 |
316365 |
|
1992 |
126054 |
453161 |
|
1993 |
138795 |
539096 |
|
1994 |
132800 |
416842 |
|
1995 |
121384 |
368158 |
|
1996 |
111431 |
246037 |
GROUP I
1. Calculate Fi corresponding to each year i.
2. Calculate the biomasses, Bi, at the beginning of each year. (Use the procedure proposed by Schaefer, that is, the biomass at the beginning of a year is approximated by the arithmetic mean of the mean biomasses of the previous and the following year).
3. Calculate the equilibrium catches, YE, which would correspond to the observed values of F.
4. Calculate the equilibrium mean biomasses,
E, which would correspond to
the observed values of F.
5. Draw the graph of
E against
Fi.
GROUP II
The Schaefer model was adjusted and the following parameters were estimated:
k = 1562851 t
r = 0.426 year-1
1. Calculate the equilibrium biomasses and the equilibrium catches corresponding to the fishing levels observed in each year, using the Schaefer model.
2. Draw, in the graph of Group I point 5, the equilibrium biomasses calculated with the Schaefer model.
3. Calculate FMSY, BMSY and YMSY
4. Calculate F0.1, B0.1 and Y0.1.
