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Appendix 4: A REVIEW OF THE STATISTICAL DATA, (LANDINGS AND FISHING EFFORT) FROM THE PORTUGUESE TRAWL FISHERY IN THE CECAF AREA, WITH SPECIAL REFERENCE TO THE HAKE FISHERY (1964-1976) by M. Lima Dias/ETUDE DES DONNES STATISTIQUES (MISES A TERRE ET EFFORT DE PECHE) DE L’EXPLOITATION DE LA ZONE COPACE PAR LES CHALUTIERS PORTUGAIS

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 tons
(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.
3. FISHING EFFORT

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).

Monteiro’s (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

CATCH PER UNIT EFFORT (kg/h)

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 = 1.07
Table 2: PORTUGUESE FISHERY IN THE CECAF AREA

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


Table 4: LENGTH COMPOSITION OF PORTUGUESE HAKE LANDINGS (No. OF FISHES × 103)

Table 5: PORTUGUESE FISHERY IN THE CECAF AREA HAKE LENGTH COMPOSITION FROM THE LANDINGS BY QUARTER TOTAL FOR 1969-1976 (Sampled vessels only)

Figure 1: PORTUGUESE LANDINGS FROM THE CECAF AREA (NORTH) - SPECIAL REFERENCE TO THE HAKE (MERLUCCIUS spp.)

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)


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