5. Results of the fishing experiments

Some of the results of the fishing experiments are commented on below. One should note, however, that most of the fishing 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 offish on the shelf. The results may thus not be directly comparable to catch rates from previous fishing surveys.

The bottom trawl used is a shrimp-cum-fish trawl (see Annex 1). It is uncertain how the efficiency of this trawl with respect to shrimp compares with the special gear used by the commercial shrimp fleet.

Suriname.

The catch records of all trawls stations are shown in Annex II, nos. 609 - 635. Table 1 shows an analysis of catch rates (standardized to kg per hours towing) for all successful bottom trawl hauls by broad groups of fish and for the inner and outer shelf separately. “Demersal” comprises the families Sciaenidae, Ariidae, Pomadasiydae, Serranidae and Lutjanidae and “Pelagic”: Engraulidae, Clupeidae, Carangidae, Scombridae. Sphyraenidae and Trichiuridae. Catch rates for pelagic fish in a bottom trawl is not very meaningful, but as during the previous surveys the indication is a higher availability on the inner shelf. The catch rates for squid were less than in the previous survey, with only one catch exceeding 20 kg/hour.

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

INNER SHELF

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
620	40	3.80			2.80	12.00	6.20
621	36	4.90	11.60		6.80	2.40	35.60
622	35	14.40			7.00	8.00	35.80
623	30	548.20	19.40		36.00	10.40	138.00
624	22	60.80		9.60	764.80		54.40
625	19	277.80	9.40	7.20	85.20		9.60
626	27	1944.00	32.00	7.30	124.00		1049.40
627	32	32.40		3.00	7.20		82.00
628	40	40.80			48.60		105.30
629	42	180.80			8.20		60.00
630	29	1.80			3.10	7.20	115.80
631	27	99.00	4.00		67.00	58.00	147.80
632	25	39.40	1.40		522.00	14.40	1.80
634	30	12.80		4.40	86.50	3.50	222.50
635	23	35.10	105.00		346.60		58.40
MEAN		219.73	12.19	2.10	141.05	7.73	141.51

OUTER SHELF

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
612	769			56.00			45.40
613	714			67.40			54.35
614	56	30.60	71.00	1.00	73.80	2.60	26.80
616	760			209.60	3.00	40.20	176.10
617	84	344.60	9.60	1.80	53.40		49.80
618	71	200.22		4.80	11.66		165.94
619	63	25.20		6.60	10.40		52.00
MEAN		85.80	11.51	49.60	21.75	6.11	81.48

Table 2 presents an analysis of catch rates by families of demersal fish for the two parts of the shelf. The inner shelf fish community is composed of a multitude of species groups, of which croakers (Orthopristis ruber, Cynoscion jamaicensis) and snappers (Lutjanus synagris, L. purpureus) were dominating. The same species of snappers were also found at the outer shelf, but at bigger sizes, and were dominating in the catches.

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

INNER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
620	40				1.40	2.40	21.00
621	36				1.30	3.60	56.40
622	35			1.00	0.80	12.60	50.80
623	30			120.00		428.20	203.80
624	22	6.40	60.80				822.40
625	19	6.00	259.20	18.60			105.40
626	27		428.00	1476.00	32.00	8.00	1212.70
627	32		2.00	10.00	4.00	16.40	92.20
628	40			33.90	3.00	3.90	153.90
629	42			88.80		92.00	68.20
630	29					1.80	126.10
631	27				3.00	96.00	276.80
632	25		14.40			25.00	539.60
634	30			4.00	5.30	3.50	316.90
635	23		4.10			31.00	510.00
MEAN		0.83	51.23	116.82	3.39	48.29	303.75

OUTER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
612	769						101.40
613	714						121.75
614	56					30.60	175.20
616	760						428.90
617	84		3.60		4.20	336.80	114.60
618	71		4.11		4.11	192.00	182.40
619	63			3.20	0.80	21.20	69.00
MEAN			1.10	0.46	1.30	82.94	170.46

Table 3 shows the standardized catch rates for the different types of pelagic fish in trawl stations from the inner and outer shelf including also hauls with pelagic trawl. Especially the bottom trawl is selective for different types of pelagic fish and Clupeids and Engraulids will be underrepresented compared with the other groups.

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

INNER SHELF

ST. NO.	DEP.	Sardines	Achovies	Carangids	Scombrids	Barracudas	Other
609	32	2.20		2.40	7.80	0.60	75.60
620	40	0.40		0.40	2.00		22.00
621	36			6.20	0.60		54.50
622	35	0.40		5.00	1.60		58.20
623	30			19.80		16.20	716.00
624	22	313.60	204.80	153.60		19.20	198.40
625	19	18.00	3.60	39.60			328.00
626	27			116.00			3040.70
627	32	2.00		2.00		3.20	117.40
628	40			48.60			146.10
629	42			4.00	4.20		240.80
630	29			3.10			124.80
631	27	1.50		30.50	35.00		308.80
632	25	219.60	273.60	2.20	26.00	0.60	57.00
633		155.20	60.80	6.80	7.40	33.60	303.20
634	30	5.00		81.50			243.20
635	23	169.40	145.60	12.60	6.40	11.20	199.90
MEAN		52.19	40.49	31.43	5.35	4.98	366.74

OUTER SHELF

ST. NO.	DEP.	Sardines	Achovies	Carangids	Scombrids	Barracudas	Other
611	94	0.80		7.40			126.30
612	769						101.40
613	714						121.75
614	56	1.00		39.20	28.60	5.00	132.00
616	760						428.90
617	84	4.20		43.20	6.00		405.80
618	71	2.06		9.60			370.96
619	63	6.80		3.60			83.80
MEAN		1.86		12.88	4.33	0.63	221.36

The catches of small pelagics on the outer shelf are generally low. On the inner shelf the average catch of clupeids, anchovies and carangids are around 50, 40 and 30 kg/hour respectively.

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

Guyana.

For records of the fishing stations reference is made to Annex II from st. 636 to 678. Table 4 shows the standardized catch rates for the broad groups and for the inner and outer shelf (shallower resp. deeper than 50 m). The mean catches by groups in the tables are in close agreement with the previous survey, except for the pelagics at the outer shelf which is considerably higher due to two relatively big catches of round sardinella.

Table 4. Guyana. Catch rates for main groups in bottom trawl stations standardized to kg/hour.

INNER SHELF

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
637	13	5.00			61.00		57.80
639	14	79.10		72.80	218.40		19.60
640	15	155.20		48.00	265.60		50.40
641	19	105.60		28.00	129.60		19.00
643	25	18.40		2.40	12.80	0.80	137.00
644	25	6.80		1.80	5.00		16.30
645	41	1.80			0.60	4.20	3.40
650	41	202.00			27.00		69.60
651	35	242.00		0.60	9.40		95.00
65n2	31	9.10		5.60	15.60	0.60	37.20
653	22	7.40		8.60	19.20		36.70
654	17	92.80	24.40	3.84	85.50		55.50
655	23	254.80	55.80		442.60		27.20
656	25	2.20			103.60	6.40	3.40
657	18	6.00			411.40		7.80
658	41	39.60			465.60		18.90
663	45	82.00		1.00	17.60		58.50
664	38	42.00	2.00	4.20	31.40		27.92
665	21	555.80			49.50		34.10
666	20	59.40	12.00		269.20		81.00
667	34	5.40	2.40		77.20	0.60	8.00
668	17	36.60		0.80	222.80		17.60
669	33	11.80	1.60	0.20	50.00		29.20
670	32	74.00	5.60		84.40		217.40
676	37	265.60	6.00		73.92		19.00
MEAN		94.42	4.39	7.11	125.96	0.50	45.90

OUTER SHELF

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
646	59	96.60			942.20		55.80
647	81	16.00			396.80	1.60	113.60
648	61	41.44		0.30	16.20	0.90	15.70
649	50	17.60			7.80		69.40
660	62				0.20	3.80	1.10
661	76	0.20			0.50	4.80	9.00
662	56	3.42		4.60	2.56		23.04
672	77	70.60		1.40	10.80		40.60
673	56	45.70	4.80	6.00	3.30		115.50
677	69	25.36	2.40	2.20	0.40		56.56
678	65	17.85		0.15	18.15	3.90	13.50
MEAN		30.43	0.65	1.33	127.17	1.36	46.71

Table 5 presents the catch rates by families for demersal fish on the inner and outer parts of the shelf. The mean catch of snappers are less than half of the previous survey for the inner shelf, while the mean rate of the grunts have increased manyfold.

Table 6 presents the catch rates analysed by families of pelagic fish. The mean rates for the various groups are approximately as in the previous surveys, but with a higher rate of sardines at outer shelf. This was due to two catches of round sardinella S. aurita within a small area.

Annex IV shows pooled length distributions of the most common species.

Venezuela.

Fishing covered the inshore fish assemblage, shrimp at intermediate depths at night and some trials for deep water shrimp in the slope down to 800 m. Record of the fishing stations are shown in Annex II from st. 679 to 695. Table 7 shows the standardized catch rates by the broad groups for all hauls including the deep water slope. Catch rates for all groups have dropped considerably since the previous survey. The decline might be caused by fish migration due to a heavy outflow of freshwater on the inner shelf.

Table 5. Guyana. Catch rates by families for demersal fish, kg/hour.

INNER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other.
637	13	4.60	5.00				114.20
639	14	16.80	79.10				294.00
640	15	36.80	155.20				327.20
641	19	15.00	105.60				161.60
643	25			1.20	13.60	3.60	153.00
644	25		3.40		3.40		23.10
645	41				0.40	1.40	8.20
646	59					96.60	998.00
650	41			127.00	3.00	72.00	96.60
651	35			188.40		53.60	105.00
652	31		5.40	0.60	2.10	1.00	59.00
653	22		2.80	3.80	0.80		64.50
654	17	7.00	92.80				162.24
655	23	9.20	254.80				516.40
656	25		1.00		1.20		113.40
657	18		6.00				419.20
663	45			16.50	7.00	58.50	77.10
664	38		42.00				65.52
665	21	7.70	213.20	332.20	4.40	6.00	75.90
666	20		55.80	3.60			362.20
667	34		5.40				88.20
66S	17	2.40	36.60				238.80
669	33		5.00			6.80	81.00
670	32					74.00	307.40
676	37	2.40	262.00	3.60			96.52
MEAN		4.08	53.24	27.08	1.44	14.94	200.33

OUTER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
646	59					96.60	998.00
647	81					16.00	512.00
648	61				0.24	41.20	33.10
649	50				1.60	16.00	77.20
660	62						5.10
661	76					0.20	14.30
662	56		0.90	0.52		2.00	30.20
672	77		3.20	4.00	2.40	61.00	52.80
673	56		27.60	1.20	6.00	10.90	129.60
677	69		12.80	0.40	8.16	4.00	61.56
678	65		1.50			16.35	35.70
MEAN			4.18	0.56	1.67	24.02	177.23

Four deep water hauls were carried out to further test the catch rates for deep water shrimp. Maximum catch was 18 kg/hour.

At intermediate depths on the shelf shrimp catches at night ranged from 3 to 8 kg/hour as also found during the previous survey.

Table 8 shows the catch rates for demersal fish in the shelf hauls and Table 9 shows the catch rates for pelagic fish by families. For all groups the catch rates are considerably lower than in the previous surveys.

Annex V shows the length distributions of some of the most common species.

Table 6. Guyana. Catch rates by families of pelagic fish in pelagic and bottom trawl hauls, kg/hour.

INNER SHELF

ST. NO.	DEP.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
637	13		23.80	8.00	29.20		62.80
639	14	36.40	120.40				233.10
640	15	105.60	100.80	8.00			304.80
641	19	10.00	6.00	1.60			264.60
642		37.04	102.86	1.37		3.09	63.60
643	25	2.60	6.60	2.00		1.60	158.60
644	25	3.00		2.00			24.90
645	41			0.60			9.40
650	41	1.00		26.00			271.60
651	35			3.00	6.40		337.60
652	31	3.00		12.00		0.60	52.50
653	22			7.40	3.80	8.00	52.70
654	17	0.56	70.34	4.20			186.94
655	23	220.60	72.00	60.00	30.00		397.80
656	25	5.00		85.80	9.60	3.20	12.00
657	18	83.20		172.80	49.80	105.60	13.80
658	41	2.80		382.20	80.60		58.50
663	45	1.00			16.60		141.50
664	38	23.40		6.40		1.60	76.12
665	21	7.70	4.40	26.40	4.40		596.50
666	20	89.40	34.20	36.00	48.00	61.60	152.40
667	34	1.20		26.80	6.00	42.80	16.80
668	17	122.80	49.60	10.40	5.60	18.40	71.00
669	33	2.40		23.60	8.40	12.00	46.40
670	32	0.40		47.40	25.00	10.40	298.20
675		37.80	172.20	74.20			1090.40
676	37	27.36	10.56				326.60
MEAN		30.53	28.66	38.08	11.98	9.96	197.08

OUTER SHELF

ST. NO.	DEP.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
646	59	894.40		47.80			152.40
647	81	128.00		268.80			131.20
648	61	0.80		4.40	5.00	6.00	58.34
649	50			3.60	4.20		87.00
660	62			0.20			4.90
661	76			0.50			14.00
662	56	1.80		0.76			31.06
672	77			0.40	10.40		112.60
673	56	0.90		1.20			173.20
677	69						86.32
678	65			3.75	6.90	6.00	36.90
MEAN		93.26		30.13	2.41	1.09	80.77

Table 7. Venezuela. Catch rates for main groups in bottom trawl stations standardized to kg/hour.

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Squid	Pelagic	Other
679	55	9.68	6.00	3.80	2.80	47.40	28.84
680	33					10.80
682	794		1.19	5.38			34.08
683	691		3.30	12.50	1.80	2.10	43.98
684	606		0.30	17.70	5.70	2.10	49.50
685	492		0.20	3.00	2.40	6.00	36.50
686	61	70.20	3.00	8.00		0.60	51.90
687	50	36.48	0.40	3.60		39.60	8.00
688	42	48.00	0.30			3.00	4.80
689	43	127.20		3.80			7.60
690	18	2.00	3.20		0.20	51.70	13.90
692	57	3.40	3.00	0.20	2.00	15.20	6.30
693	43	24.60				5.70	0.60
694	32	72.60	1.40			77.70	2.50
MEAN		29.85	1.59	4.16	1.06	21.05	21.16

Figure 1. Course tracks, fishing stations and hydrographic profiles.

Table 8. Venezuela. Catch rates by families for demersal fish, kg/hour.

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
679	55		4.40	0.08	0.40	4.80	88.84
680	33						10.80
686	61		5.40	4.20	6.00	54.60	63.50
687	50		38.36		0.12		51.60
688	42		48.00				8.10
689	43		127.20				11.40
690	18		2.00				69.00
692	57		1.20		0.40	1.80	26.70
693	43		24.60				6.30
694	32		69.60	3.00			81.60
MEAN		0.62	34.26	0.73	0.69	6.12	45.24

Table 9. Venezuela. Catch rates by families of pelagic fish in pelagic and bottom trawl hauls, kg/hour.

ST. NO.	DEP.	Anchovies	Sardines	Carangids	Scombrids	Hairtails	Other
679	55		13.80	14.80	2.80	10.80	56.32
680	33			10.80
606	61					0.60	133.10
687	50		10.80	0.40		26.00	52.88
688	42					3.00	53.10
689	43						138.60
690	18	3.20	5.30		11.00	32.20	19.30
692	57		0.80	2.60	3.20	1.80	21.70
693	43		0.90		1.80		28.20
694	32	2.80	34.50	24.40		16.00	76.50
MEAN		1.32	6.97	6.98	2.28	9.16	60.95

Figure 2. a) Hydrographic profiles. WEST OF MARONI RIVER 12.8 1988

Figure 2. b) Hydrographic profiles. EAST OF DEMARARA RIVER 17.8.1988

Figure 2. c) Hydrographic profiles. ORINOCO 20-21.8 1988

Figure 3. Distribution of pelagic fish from acoustic system.