WITH SPECIAL REFERENCE TO THE HAKE FISHERY
(1964-1976)
by
M. Lima Dias
Instituto Nacional Investigação das
Pescas
Lisboa, Portugal
1. INTRODUCTION
During the Third Session of the CECAF Working Party on Resource Evaluation (Rome 1976), it was realized that the only reliable effort and corresponding catch data on hakes available were the Portuguese data. The Working Party recommended that Portuguese scientists fully process and analyse all such data in the Lisbon Fisheries Laboratory and report such data to the CECAF Secretariat.
The present paper describes the results obtained after a complete revision of the total landings and fishing effort of the Portuguese trawl fleet. Some discrepancies were detected between the reviewed data and those submitted to the CECAF working party. This can be interpreted as a result of the Portuguese statistical system as well as unavailability of log books at the time from trawlers. In spite of these difficulties it has been possible to update landings and fishing effort from 1964 to 1976.
Fishing effort for the years 1964-1967 has been estimated for some of the trawlers using data of sister vessels fishing in the same area and time.
It has been difficult to separate the landings of the Portuguese fleet by species and CECAF statistical divisions. However it can be said that more than 90 percent of the hake landed are Merluccius senegalensis. It should be noted that Portuguese trawlers fish mainly in CECAF divisions 34.1.3, 34.3.1 and 34.1.1.
2. LANDINGS STATISTICS
The present review of the landing statistics is independent of any data already submitted to FAO. Data have been collected from log books of captains, fishing companies, the statistics branch of the Instituto Nacional Investigação das Pescas, as well as miscellaneous information obtained from the fishing port.
Total landings as well as those of hakes for the Portuguese fleet fishing in the northern zone of the CECAF area for the period 1964-1976 are presented in Table 1 and Fig. 1. Table 1 also contains live weight of hakes. The raising factor used for converting gutted fish to live weight equivalent is f = 1.07.
Table 2 contains total landings of Portuguese trawlers as well as those of hakes for 1964-1976 by vessel categories.
Four categories of trawlers (side and bottom) were considered, namely:
(a) vessels with GRT below 299 tons3. FISHING EFFORT
(b) vessels with GRT between 300 and 399 tons
(c) vessels with GRT between 399 and 499 tons
(d) vessels with GRT higher than 500 tons.
Fishing effort data for the Portuguese fleet have been presented in Table 1. These are: number of fishing vessels, number of hauls and number of hours fishing. At the bottom of the table are presented figures of catch per unit effort (c.p.u.e) (kg/h). These data are accurate enough to be used in future studies.
The fishing effort data have also been broken down by vessel categories. These are presented in Table 3 and Figures 2, 3 and 4. Trawlers with GRT below 299 tons were not operating after 1975. It should be noted that main vessels operating after 1975 are between 300 and 500 tons GRT.
It has not been possible to estimate fishing effort for hakes only.
4. BIOLOGICAL DATA
Between 1967 and 1976 sampling for length composition of hake landings were carried out. The samples were obtained on board commercial trawlers (during 1969) and at the main fishing harbour, in Lisbon. The samples, in this last case, were stratified according to three, size categories of hake landed. However for the final treatment of the data (length compositions for the total landings) it was not possible to extend the figures to the fleet, because the final statistics give only the total weight of the landings and not by size categories.
Total length composition of hake landed from 1969 to 1976 are presented in Table 4 and Fig. 5 by 2 cm groups.
In order to obtain the live weight of the fish in the catch, a raising factor of 1.07 was applied to the gutted weight (in Table 4 these values are referred to as T × 1.07).
Monteiros (1969) length/weight relationship W = .0111 × L2.886 was applied to numbers of fish to obtain the theoretical live weight as a check on the live weight.
In Table 5 and Fig. 6 are presented length composition data by quarter. (Summary of 1969-1976). In Fig. 6 one can follow quarterly variations in the length distribution.
Unfortunately it was completely impossible to carry out any studies on hake life cycle, in order to understand the evaluation of the stock(s).
Table 1: PORTUGUESE FISHERY IN THE CECAF AREA LANDING AND EFFORT STATISTICS
Years |
Landings (ton.) |
Fishing Effort |
|||||
Total fishery |
Hake |
No. of ships fishing |
No. of trips |
No. of hauls |
No. of fishing hours |
||
landed |
live weight |
||||||
1964 |
43 248 |
6 181 |
6 614 |
46 |
472 |
41 784 |
152 871 |
1965 |
43 061 |
12 220 |
13 075 |
47 |
467 |
40 542 |
150 824 |
1966 |
40 792 |
13 592 |
14 543 |
45 |
437 |
39 231 |
149 137 |
1967 |
39 024 |
13 487 |
14 431 |
45 |
375 |
32 841 |
132 380 |
1968 |
37 774 |
14 195 |
15 189 |
42 |
371 |
34 686 |
137 754 |
1969 |
37 072 |
12 964 |
13 871 |
43 |
359 |
33 832 |
137 567 |
1970 |
32 322 |
9 566 |
10 236 |
44 |
338 |
36 053 |
142 596 |
1971 |
27 123 |
7 298 |
7 809 |
40 |
271 |
31 279 |
113 896 |
1972 |
28 156 |
6 861 |
7 341 |
35 |
265 |
32 209 |
109 308 |
1973 |
31 405 |
9 281 |
9 931 |
35 |
267 |
32 855 |
106 504 |
1974 |
26 106 |
8 737 |
9 349 |
34 |
227 |
26 768 |
81 266 |
1975 |
20 572 |
3 982 |
4 261 |
35 |
193 |
25 663 |
78 247 |
1976 |
20 933 |
4 701 |
5 030 |
34 |
190 |
24 529 |
80 542 |
TOTAL |
427 588 |
123 065 |
131 680 |
|
4 232 |
432 272 |
1 572 892 |
1964 |
1965 |
1966 |
1967 |
1968 |
1969 |
1970 |
1971 |
1972 |
1973 |
1974 |
1975 |
1976 |
43.3 |
86.7 |
97.5 |
109.0 |
110.2 |
100.8 |
71.8 |
68.6 |
67.2 |
93.2 |
115.0 |
54.5 |
62.5 |
conversion factor f = 1.07Table 2: PORTUGUESE FISHERY IN THE CECAF AREA
TOTAL LANDINGS (tons) - CATCHES FOR ALL SPECIES (a), CATCHES OF HAKE (b), AND FISHING EFFORT HOURS FISHING (c), BY GRT VESSELS CATEGORIES
Table 3: PORTUGUESE TRAWL FISHERY IN THE CECAF AREA (NORTH) NUMBER OF TRIPS BY VESSEL CATEGORIES (GRT), AND CORRESPONDING FISHING HOURS × 103
(a): N° of trips |
(b): N° of fishing hours ×
103 |
Tonnage classe |
1964 |
1965 |
1966 |
1967 |
1968 |
1969 |
1970 |
1971 |
1972 |
1973 |
1974 |
1975 |
1976 |
TOTAL |
||||||||||||||
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
|
GRT £ 299 |
46 |
12 |
37 |
10 |
21 |
7 |
18 |
6 |
18 |
6 |
15 |
5 |
21 |
9 |
22 |
8 |
20 |
7 |
16 |
5 |
10 |
2 |
- |
- |
- |
- |
244 |
77 |
300 < GRT £ 399 |
201 |
60 |
194 |
57 |
189 |
58 |
153 |
49 |
139 |
51 |
147 |
54 |
139 |
56 |
95 |
38 |
88 |
34 |
71 |
24 |
66 |
23 |
49 |
17 |
61 |
24 |
1592 |
545 |
400 < GRT £ 499 |
178 |
64 |
186 |
65 |
181 |
67 |
157 |
60 |
169 |
63 |
166 |
64 |
150 |
60 |
123 |
49 |
132 |
55 |
151 |
63 |
126 |
47 |
114 |
47 |
111 |
48 |
1944 |
752 |
GRT > 500 |
47 |
17 |
50 |
18 |
46 |
17 |
47 |
18 |
45 |
13 |
31 |
14 |
28 |
18 |
31 |
18 |
25 |
13 |
29 |
14 |
25 |
10 |
30 |
15 |
18 |
9 |
452 |
199 |
TOTAL |
472 |
153 |
467 |
150 |
437 |
149 |
375 |
133 |
371 |
133 |
359 |
137 |
338 |
143 |
271 |
113 |
265 |
109 |
267 |
106 |
227 |
82 |
193 |
79 |
190 |
81 |
4232 |
1573 |
Figure 2: PORTUGUESE TRAWL FISHERY CECAF AREA (NORTH) NUMBER OF TRIPS BY VESSEL CATEGORY (GRT)
Figure 3: PORTUGUESE TRAWL FISHERY IN THE CECAF AREA (NORTH) FISHING EFFORT (ALL FLEET)
Figure 4: PORTUGUESE TRAWL FISHERY IN THE CECAF AREA (NORTH) FISHING EFFORT BY DIFFERENT GRT
Figure 5: PORTUGUESE TRAWL FISHERY IN THE CECAF AREA (NORTH) LENGTH COMPOSITION OF HAKE LANDINGS
Figure 6: PORTUGUESE HAKE FISHERY IN THE CECAF AREA (NORTH) TOTAL SAMPLING BY QUARTERS (1969-1976)