5. Results of fishing experiments.

The bottom trawl survey forms part of a programme for “swept area” biomass estimation, and for this purpose the trawl stations are positioned in advance more or less randomly and with no intention of obtaining high catch rates. The catch rates thus do not simulate those of a commercial fishery and they are presented here merely to give a rough impression of the general occurrence, composition and abundance of fish on the shelf. The data from the prepositioned trawl hauls will later be used for estimates of biomass of demersal species.

The bottom trawl used is a shrimp-cum-fish trawl (see Annex 1) and it may not be as efficient for shrimp as specially designed shrimp-trawls.

Oriente.

The fish on the shelf between Bocas de Dragon and Cabo Codera is grouped as in the previous cruise report: an assemblage of the inner pan of the shelf, inside the Testigos Archipelago and the Margarita Island and on the coastal side of the Cariaco Trench in which cattish and croakers are the most common groups of the demersals; and one assemblage found over the outer parts of the shelf outside the Testigos and Margarita Island and westwards past the Tortuga Island where the demersal fish is dominated by snappers. This grouping is used in the following description of the composition and catch rates of the fishing experiments. The complete record of all hauls made are shown in Annex II. Stations 455 to 508 and the position of the stations can be seen in Figure 1.

Table 1 shows an analysis of catch rates (standardized to kg per hours towing) for all successfull bottom trawl hauls by broad groups of fish and for the inner and outer shelf separately. “Pelagic” comprises Clupeidae(sardines), Engraulidae(anchovies), Carangidae, Scombridae, Sphyraenidae(barracuda) and Trichiuridae(hairtails). “Demersal” includes the families Sciaenidae(croakers), Lutjanidae(snappers), Pomadasidae(grunts), Serranidae(groupers), Ariidae(catfish) and Priacanthidae(glasseyes). Catch rates of demersal fish are high, averaging 361 kg/hour on the inner shelf and 180 kg/hour on the outer shelf, compared to the respective 200 kg/hour and 110 kg/hour obtained in the previous bottom trawl survey of these areas in February-March. Squids are present in nearly all catches at about the same rates as in the previous survey and shrimps are scarce. Table 2 shows the catch rates by families for the demersal fish by inner and outer shelf parts. As in previous survey catfish and croakers dominate the inner part and snappers the outer part of the shelf.

Table 1. ORIENTE. Catch rates for main groups in bottom trawl stations standardized to kg/hour.

INNER

ST. NO.	DEP.	Pelagic	Demersal	Shark	Squid	Shrimp	Other
455	61	105.90	4.80	15.60	14.10		106.20
456	65	2.40	284.80		8.00		129.60
462	33	18.30	12.30		17.00		1.60
463	37	5.43	37.29		31.43		11.28
464	35	252.10	19.00		40.00	3.00	65.50
466	43	107.40	213.00	16.00	40.00	4.00	169.60
467	33	8.00	107.60	10.00	84.00	6.20	114.00
484	65	171.60	511.00	80.60		5.60	171.60
485	20	858.00	2220.00				1059.60
486	71	368.00	911.20	36.80	12.00	3.30	252.30
488	49	11.88	398.16		10.80	1.08	12.72
490	149	108.80	456.00		65.60	49.60	179.20
491	111	144.40	800.90	5.00	60.80	1.80	87.70
492	81	22.34	87.90	40.00	13.50		60.78
493	41	5126.07	16.80
494	43	25.94	28.34		9.60	1.20	21.00
495	78	17.70	39.00	11.40	12.00		83.22
MEAN		432.60	361.65	12.67	24.64	4.46	148.58

OUTER

ST. NO.	DEP.	Pelagic	Demersal	Shark	Squid	Shrimp	Other
458	71	201.60	115.40		24.60		42.20
460	61	15.00	157.00	7.40	11.00	1.00	139.00
461	35	82.00	19.60	22.00	27.20	0.20	43.00
468	44	35.80	28.00	0.70	12.50	0.30	32.30
469	65	1417.30	374.50	0.80	62.10		8.10
470	44	1501.70	3.10		28.60		17.10
471	73	717.50	832.40		17.20		85.90
472	28	15.90	2.70		15.30		20.70
473	49	315.00	171.00		61.80	1.20	74.00
474	26	67.20	56.40		81.60		69.60
477	148	6.00	44.40				50.16
478	59		46.92		1.20		145.92
479	77	140.80	351.50		9.90		235.40
480	69	371.40	421.40		98.00		134.40
481	50	175.20	221.80		157.20	1.60	182.40
482	91	10.50	372.15	42.00	10.50		225.75
483	96	105.60	317.60		2.40		43.40
496	81	80.00	166.50			0.40	54.50
499	97	193.90	188.20		11.20		42.50
500	99		74.28		3.36		13.20
501	128	274.80	100.98		0.90		21.00
502	78	99.25	14.66		6.68		31.88
503	92	0.60	1.50		7.80		13.00
504	33	0.80	457.90	12.40			351.90
505	71	102.40	344.40		2.40		15.40
506	75		1.00		0.80		7.36
507	77		136.61		2.31		3.46
508	72		25.00		2.80		10.20
MEAN		211.79	180.25	3.05	23.55	0.17	75.49

Table 3 shows the catch rates for the different types of pelagic fish. Catch rates of pelagic fish in bottom hauls are not very meaningful and as the Table shows the rates and composition of species vary considerably by stations. One large catch of anchovies was taken on the inner coast of the Cariaco trench (Annex II, St. No. 493) and one good sardine catch was obtained north of the Margarita Island (St. No. 470). Most of the pelagic catches were dominated by carangids with some good catches of hairtails, scombrids and barracudas. Present catch rates are higher but species composition of pelagic fish are mostly the same as observed in February-March.

Table 2. ORIENTE. Catch rates by families for demersal fish, kg/hour.

INNER

ST. NO.	DEP.	Croakers	Catfish	Grunts	Groupers	Glasseyes	Other
455	61	4.80					241.80
456	65			6.40	1.60	1.60	415.20
462	33			1.40	0.50		47.30
463	37			0.29	3.57	5.71	75.86
464	35	13.00	2.00	2.50	1.00	0.50	360.60
466	43	110.60	35.20	6.40	26.40	24.00	347.40
467	33	3.60		52.00	18.00	4.00	252.20
484	65	340.60		117.00	19.60		463.20
485	20	100.80	1690.00	191.80	159.40	78.00	1917.60
486	71	883.20		16.00	7.20	1.60	675.60
488	49	347.40	40.68	6.84	3.24		36.48
490	149	412.80					446.40
491	111	729.90			5.70	52.00	313.00
492	81			2.10		37.80	184.62
493	41	8.23	4.46			4.11	5126.07
494	43				1.04	2.10	82.94
495	78					9.00	154.32
MEAN		173.82	104.26	23.69	14.54	12.97	655.33

OUTER

ST. NO.	DEP.	Croakers	Snappers	Grunts	Groupers	Glasseyes	Other
458	71		101.60	3.60		10.20	268.40
460	61		139.00		1.50	16.50	173.40
461	35		19.60				174.40
468	44		26.20		1.80		81.60
469	65		165.00		34.00	175.50	1488.30
470	44				2.00	1.10	1547.40
471	73		724.40	25.80	56.40	25.80	820.60
472	28				2.70		51.90
473	49		136.80		30.60	3.60	452.00
474	26		2.40	17.20	32.40	4.40	218.40
477	148		3.36		41.04		56.16
478	59		1.92	10.80	0.60	33.60	147.12
479	77		185.40	99.40	66.70		386.10
480	69		403.20			18.20	603.80
481	50		178.00		40.80	3.00	516.40
482	91		342.30		29.85		288.75
483	96	19.20	265.60	25.60		7.20	151.40
496	81		131.00		0.50	35.00	134.90
499	97		145.20	4.20	36.40	2.40	247.60
500	99		9.36	52.44	12.48		16.56
501	128		97.50		0.48	3.00	296.70
502	78		11.57			3.09	137.81
503	92		0.50		1.00		21.40
504	33		373.90	4.40	5.00	74.60	365.10
505	71		149.20	195.20			120.20
506	75				1.00		8.16
507	77			135.23	1.38		5.77
508	72		21.20	3.80			13.00
MEAN		0.69	129.79	20.63	14.24	14.90	314.05

Western part, from Cabo Codera to Peninsula de Guajira.

Results of the bottom hauls between Cabo Codera and Cabo San Roman are summarized in Table 4. Mean catch rate of demersal is 90 kg/hour or about half the rate obtained on the outer Oriente coast. This catch rate is however more then twise that of the demersal fish catch obtained in the bottom trawl survey of the area in February-March. The record catch of 546 kg/hour (St. No. 517) was obtained at night on the small bank north of La Guaira, consisting of good zised snappers mainly. The poorest catches were encountered on the Cabo Codera coast (St. Nos. 513-515). 4 hauls were made on the slope from 200-300 m. to test the availability of deep sea shrimps, and the rates obtained are around 6 kg/hour. The pelagic species are also less abundant in the trawl catches then further to the east, and confirmes the results of the acoustic stock measurements. The family composition of the pelagic and demersal species is shown in Tables 5 and 6 respectively. The latter is dominated by snappers whereas the pelagics consist of carangids, hairtails and sardines mainly.

Table 3. ORIENTE. Catch rates by families of pelagic fish in bottom trawl hauls, kg/hour.

INNER

ST. NO.	DEP.	Sardines	Hairtails	Carangids	Scombrids	Barracuda	Other
455	61	0.90	0.60	90.00	1.50	12.90	140.70
456	65			2.40			422.40
462	33	1.70		1.20		15.40	30.90
463	37			0.43	0.14	4.86	80.00
464	35	154.50		27.50	28.60	41.50	127.50
466	43	23.20	40.00	44.20			442.60
467	33	8.00					321.80
484	65	13.00	15.60	143.00			768.80
485	20			185.20	308.80	364.00	3279.60
486	71	5.60	260.80	54.40		47.20	1215.60
488	49	1.44	2.52	7.92			422.76
490	149		80.00	28.80			750.40
491	111		95.00	49.40			956.20
492	81		9.60	5.24		7.50	202.18
493	41		6.86	27.78		9.60	5098.63
494	43	7.80		1.64			76.64
495	78			13.50		4.20	145.62
MEAN		12.71	30.06	40.15	19.94	29.83	851.90

OUTER

ST. NO.	DEP.	Sardines	Hairtails	Carangids	Scombrids	Barracuda	Other
458	71	3.60		198.00			182.20
460	61			15.00			315.40
461	35	32.40		32.20	8.20	9.20	112.00
468	44			0.80	25.60	9.40	73.80
469	65	251.10		845.20	321.00		445.50
470	44	1471.80		29.90			48.80
471	73			717.50			935.50
472	28	3.90		4.50	7.50		38.70
473	49	291.60		9.00		14.40	308.00
474	26	29.60		23.20	8.00	6.40	207.60
477	148			6.00			94.56
478	59						194.04
479	77			140.80			596.80
480	69	4.20		347.20	20.00		653.80
481	50	7.20		129.60	38.40		563.00
482	91			8.40	2.10		650.40
483	96			104.00	1.60		363.40
496	81			35.00		45.00	221.40
499	97		8.40	185.50			241.90
500	99						90.84
501	128			274.80			122.88
502	78	0.51		83.31	15.43		53.22
503	92			0.60			22.30
504	33	0.10		0.70			822.20
505	71			102.40			362.20
506	75						9.16
507	77						142.38
508	72						38.00
MEAN		74.86	0.30	117.63	15.99	3.01	282.50

Table 4. VENEZUELA, WESTERN PART. Catch rates for main groups in bottom trawl stations standardized to kg/hour.

ST. NO.	DEP.	Pelagic	Demersal	Shark	Squid	Shrimp	Other
509	63		110.30	14.80	5.00		18.60
510	183	10.00	138.00		2.00		39.60
511	153	427.20	121.20	8.00	2.40		52.60
512	66	6.25	144.63		3.75		13.13
513	65	27.60	14.50		1.80		8.20
514	93	36.20	4.60		4.40		22.60
515	67	0.84	12.96		2.40		38.04
516	215	16.80	61.40		3.60	6.60	57.00
517	101	81.60	546.00				270.80
518	77	8.30	37.60		7.00		55.70
519	73	6.40	55.40	7.00	5.00		57.40
520	45	60.60	133.60				3.60
521	66	109.20	72.60		6.00		17.20
522	60	36.48	65.04		1.68		17.28
523	106	72.43	156.63		7.71		195.00
524	252	0.60			8.70	5.85	75.10
525	233		11.05		5.21	4.89	68.07
526	264	0.15			8.85	5.55	26.69
527	59	289.60	106.60		4.80		25.60
528	79	49.60	22.80		1.50		19. 10
529	60	8.40	97.00		4.20		13.80
530	69	55.60	43.10		18.00		6.60
531	22	20.00	50.40		3.20		55.80
532	49	3.20	89.40		3.40		6.20
533	37	43.00	161.60		2.20		6.80
MEAN		54.80	90.26	1.19	4.51	0.92	46.82

Table 5. VENEZUELA, WESTERN PART. Catch rates by families for pelagic fish in bottom trawl hauls, kg/hour.

ST. NO.	DEP.	Sardines	Hairtails	Carangids	Scombrids	Barracudab	Other
509	63						148.70
510	183			10.00			179.60
511	153		426.00	1.20			184.20
512	66			6.25			161.51
513	65	1.00		26.60			24.50
514	93			35.80	0.40		31.60
515	67			0.84			53.40
516	215			16.80			128.60
517	101			81.60			816.80
518	77			8.30			100.30
519	73			6.40			124.80
520	45			6.60	9.00	45.00	137.20
521	66	65.60		43.60			95.80
522	60	3.12		32.64			84.72
523	106			60.86	11.57		359.34
524	252		0.60				89.65
525	233						89.22
526	264		0.15				41.09
527	59	157.20	3.20	72.40	55.60	1.20	137.00
528	79		2.60	32.10	14.90		43.40
529	60			7.40		1.00	115.00
530	69			55.40	0.20		67.70
531	22			17.60	2.40		109.40
532	49	0.80		1.00	0.40	1.00	99.00
533	37			32.60	10.40		170.60
MEAN		9.11	17.30	22.24	4. 19	1.93	143.73

Table 6. VENEZUELA, WESTERN PART. Catch rates by families for demersal fish, kg./hour.

ST. NO.	DEP.	Croakers	Snappers	Grunts	Groupers	Glasseyes	Other
509	63		102.70				46.00
510	183		138.00				51.60
511	153		87.60		33.60		490.20
512	66		137.25			7.38	23.13
513	65		6.10			8.40	37.60
514	93		4.40			0.20	63.20
515	67		4.08			6.48	43.68
516	215	1.80	59.40		0.20		84.00
517	101		459.00		59.00	28.00	352.40
518	77	1.80	25.80			1.00	80.00
519	73		29.60			8.00	93.60
520	45		104.60			5.00	88.20
521	66		70.60			2.00	132.40
522	60		63.12		0.24		57.12
523	106		156.63				275.14
524	252						90.25
525	233		11.05				78.17
526	264						41.24
527	59		100.20			6.40	320.00
528	79		22.00			0.80	70.20
529	60		94.80				28.60
530	69		40.70			0.20	82.40
531	22		29.20			5.60	94.60
532	49		70.80	0.40		2.20	28.80
533	37		135.20			1.00	77.40
MEAN		0.14	78.11	0.02	3.72	3.31	113.20

In the Gulf of Venezuela the catch data have been grouped in an inner and outer part as in the previus survey in February-March, with a north/south dividing line from Punto Fijo and westward. The catch rate by broad groups are shown in Table 7. The average catch of demersals in the inner pan is 52 kg/hour compared to 61 kg/hour obtained in the previous coverage. For the outer part of the gulf, the respective catch figures are 54 kg/hour and 24 kg/hour. The best catches of squids and shrimps were obtained in the innerpart of the gulf, on the eastern and western side respectively. The record catch of squids is 54 kg/hour, and for shrimps the record is 57 kg/hour. Catch rate by family groups are shown in Tables 8 and 9 for pelagics and demersals respectively. The pelagics are dominated by carangids, the demersals by snappers(outer-) and croakers (inner part).

Pooled samples of the length compositions of the most common species are shown in Annex III.

Table 7. GULF OF VENEZUELA. Catch rates for main groups in bottom trawlstations standardized to kg/hour.

INNER PART

ST. NO.	DEP.	Pelagic	Demersal	Shark	Squid	Shrimp	Other
538	19	264.20	76.80		15.60	1.60	40.80
539	15	36.10	30.20	0.40	1.00	8.60	7.80
540	23	518.00	85.20	3.60		2.80	28.00
541	20	597.62	50.47	9. 18		0.71	41.29
542	21	372.00	13.80		4.80		10.80
543	15	216.00	81.60	21.00	6.00	57.00	31.40
544	13	96.80	78.60	8.80		11.20	25.80
545	15	152.60	111.30		1.00	29.00	7.60
546	14	156.00	64.20		6.00	6.00	55.80
547	24	120.69	74.07			1.03	28.81
548	32	45.20	83.60		13.60	3.40	76.00
549	28	233.20	20.50		54.00		16.50
550	40	298.20	2.50		6.00		1.50
551	40	283.90	2.20		22.40		79.10
552	36	406.00	4.60		24.00		28.80
MEAN		253.10	51.98	2.87	10.29	8.09	32.00

OUTER PART

ST. NO.	DEP.	Pelagic	Demersal	Shark	Squids	Shrimp	Other
534	29		10.60			0.30	1.20
535	74	25.90	1.60		3.10		6.70
536	69	25.94	62:00		2.70		27:14
537	70	26.54	29.60		5.40		32.84
553	49	1163.70	4.50		23.60	0.20	237.40
554	50	699.40	100.40		11.70	0.30	39.40
555	43	400.40	9.60		42.00		12.60
656	45	26.72	2.73		10.36	0.09	11.19
557	56	96.60	81.20		2.40	0.60	57.40
558	17	15.60	27.40		3.60	13.60	68.40
559	12	62.90	23.00		1.00	4.80	19.60
560	54	49.30	2.10	3.80	4.60		3.50
561	59	77.70	2.40		3.80	0.60	11.30
562	60	174.00	95.00		4.00		63.70
563	61	28.24	44.40		5.00		79.00
564	52	472.64	235.09		4.36		89.45
565	29	2.80	38.00	2. 00			91.40
566	15	58.00	75.80	2.00	1.00	4.80	108.80
567	70	19.50	180.30		4.00	3.00	44.00
MEAN		180.31	53.99	0.41	6.98	1.49	52.90

Table 8. GULF OF VENEZUELA. Catch rates by families for pelagic fish in bottom trawl hauls, kg/hour.

INNER PART

ST. NO.	DEP.	Sardines	Anchovies	Carangids	Hairtails	Barracudas	Other
538	19	212.40		35.00	16.80		134.80
539	15	10.50	5.90	0.50	19.20		48.00
540	23	121.80		95.20	301.00		119.60
541	20	158.29		352.15	87.18		101.65
542	21	31.20	1.20	295.20		21.60	52.20
543	15	52.00	68.00	20.00	62.00		211.00
544	13	37.20	15.60	16.00	28.00		124.40
545	15	41.60	17.00	5.00	89.00		148.90
546	14	108.60		36.60	3.60		139.20
547	24	50.06	28.80	28.11	6.86	6.86	103.91
548	32	32.40		11.20			178.20
549	28	27.00	24.00	164.70		17.00	91.50
550	40	133.00		154.00			21.20
551	40			225.00	6.40	51.80	104.40
552	36			399.20		1.80	62.40
MEAN		67.74	10.70	122.52	41.34	6.60	109.42

OUTER PART

ST. NO.	DEP.	Sardines	Scombrids	Carangids	Barracuda	Hairtails	Other
534	29						11.80
535	74	0.50		1.20	23.80	0.40	11.70
536	69	2.10	0.74	6.30	16.80		91.84
537	70	0.44	9.90	7.80	8.40		67.84
553	49	25.00	0.20	127.50	23.60	987.40	265.70
554	50	176.80	23.40	148.20	286.00	65.00	151.80
555	43	128.80	42.00	201.60	26.60		65.60
556	45	0.27	0.91	2.18	2. 73		45.00
557	56		4.20	13.20	78.80	0.40	141.60
558	17	8.40	1.20	2.40			116.60
559	12	29.60	6.60	3.10		19.60	52.40
560	54	1.20	36.00	1.40	0.80	6.80	17.10
561	59	0.40	1.80	40.50	3.00	32.00	18.10
562	60	1.00	1.00	102.00	70.00		162.70
563	61	1.74	1.00	21.50	3.50		128.90
564	52	34.91	10.09	384.00	43.64		328.90
565	29	0.40		1.60	0.80		131.40
566	15	9.00	4.60	17.40	2.00	25.00	192.40
567	70	1.50	1.00	17.00			231.30
MEAN		22.21	7.61	57.84	31.08	59.82	117.51

Table 9. GULF OF VENEZUELA. Catch rates by families for demersal fish, kg./hour.

INNER PART

ST. NO.	DEP.	Croakers	Snappers	Grunts	Groupers	Perilus	Other
538	19	72.40	4.40			2.80	319.40
539	15	30.20				3.00	50.90
540	23	71.60	13.60			18.20	534.20
541	20	50.47				34.41	614.39
542	21		13.80			10.80	376.80
543	15	81.60				9.00	322.40
544	13	78.60					142.60
545	15	109.70	1.60			3.00	187.20
546	14	64.20					223.80
547	24	46.29	3.43	24.35			150.53
548	32	4.80		58.40	14.00		144.60
549	28	15.00		3.00	2.50		303.70
550	40						308.20
551	40	2.20				77.00	308.40
552	36		3.60			28.80	431.00
MEAN		41.80	2.70	5.72	1.10	12.47	294.54

OUTER PART