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
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.

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 × L^2.886 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

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

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)