5. RESULTS OF FISHING EXPERIMENTS

Suriname
Guyana
Venezuela and the Joint Fishing Area south of Trinidad

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 of fish 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) and it may not be as efficient for shrimp as specially designed shrimp-trawls.

The fish fauna of the Guianas shelf region has been described as assemblages of “brown and golden” euryhaline fish on onshore mud bottoms down to abt. 25 fathoms represented mainly by the families Ariidae, Sciaenidae and Dasyatidae followed by “red” fish on sandy and relic coral bottom further offshore represented by Lutjanidae, Serranidae and Pomadasyidae. Predominantly pelagic fish described as “silver” fish and represented by Carangids and Scombrids are considered as migrants and inhabit mainly the “red” fish zone. The findings of the present survey confirm the main features of this picture relating to the demersal fish with some modifications. For the area to the west of the narrow part of the shelf at abt 59° W off Guyana the “inner shelf” fauna with a predominance of croakers was found to extend down to a depth of about 60 m. As regards the pelagic fish to which should be added Engraulidae and Clupeidae they were found in highest density in the depth zone 10 - 20 fathoms, although they also, with the exception of Engraulids, inhabit the outer shelf.

In the following analyses the “inner shelf” refers to the depth zone 10-40m for Suriname and eastern Guyana, and 10-60m further west. The “outer shelf” then forms the remaining part down to abt. 100m.

Suriname

The catch records of all trawls stations are shown in Annex II, nos. 1-44. 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 and Lutjanidae and “Pelagic”: Engraulidae, Clupeidae, Carangidae and Scombridae. Mean catch rates are highest on the inner shelf for both demersal and sharks. Catch rates for pelagic fish in a bottom trawl is not very meaningful, but the indication is a higher availability on the inner shelf. Table 2 presents an analysis of catch rates by families of demersal fish and of squid for the two parts of the shelf. The predominance of catfish and croakers on the inner shelf and of snappers and grunts on the outer is evident. Stations 27 and 40 from the inner shelf with relatively high rates of snappers and grunts were taken in abt. 30m of depth.

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

INNER SHELF

STA. NO.	Demersal	Sharks	Shrimp	Pelagic	Other
1	459.4	87.4	100.8	174.4	605.4
2	14.4	6.0	1.2	13.7	86.6
3	9.8			203.3	60.7
15	24.9	24.6	5.8	39.4	94.2
16	0.2		0.9	25.0	4.2
25	320.8	17.0	2.2	96.2	232.4
26		5.0		22.0	9.0
27	338.6	68.2		1022.2	54.0
28	0.4			17.6	47.0
38	296.7	22.0	4.8	312.4	195.3
39	1085.6	1.1	2.0	496.0	380.6
40	194.5			15.5	133.6
41	9.0			149.7	17.4
42			0.2	59.0	6.0
43	9.8	12.0		254.8	73.4
MEAN	184.2	16.2	7.8	193.4	133.3

OUTER SHELF

STA. NO.	Demersal	Sharks	Shrimp	Pelagic	Other
5	6.0		4.0	6.8	6.2
8	148.8			46.8	22.9
9	95.0	2.0	0.3	39.8	35.6
10	176.8			158.8	111.8
12	51.6	6.4	0.2	229.2	66.2
13	152.4	6.4		72.6	41.0
17	143.0	2.2		7.2	19.8
18	44.5	8.4		29.4	16.9
20	43.4	24.2		47.2	12.4
21	103.0	2.2		138.8	5.8
22	1.1			32.4	6.2
31	235.6	20.0		12.2	16.4
32	235.2			106.0	25.4
33	164.0			46.8	2.0
34	174.4			327.2	3.2
35	24.0			201.6	43.4
36	2.1	5.0		25.0	7.1
MEAN	105.9	4.52	0.2	89.8	26.0

The dominant species among the croakers were the green - and acoupa weakfishes Cynoscion virescens and C. acoupa and the king weakfish Macrodon ancylodon. The Corocoro grunt, Orthopristis ruber was the most common species of this family. Among the large snappers southern red snapper Lutjanus purpureus dominated together with lane snapper L. synagris while vermillion snapper Rhomboplites aurorubens was the most common of the smaller Lutjanids. Pooled samples of size compositions of these species are shown in Annex III.

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

INNER SHELF

STA. NO.	Catfish	Croakers	Grunts	Snappers	Squid	Other
1	100.8	358.6				968.0
2	5.0	9.4				107.5
3		9.8				264.0
15	5.0	19.9			1.2	162.8
16		0.2				30.1
25	30.6	263.0	13.6	13.6		347.8
26						36.0
27			56.2	282.4		1144.4
28				0.4	44.4	20.2
38	22.6	274.1			3.3	531.2
39		1057.8	8.2	19.6		879.7
40			17.3	177.2		149.1
41		9.0			10.8	156.3
42					3.4	61.8
43	1.6	8.2				340.2
MEAN	11.0	134.0	6.3	32.8	4.2	346.6

OUTER SHELF

STA. NO.	Catfish	Croakers	Grunts	Snappers	Squid	Other
5		5.6	0.4			17.0
8			12.0	136.8	2.6	67.1
9		0.8	3.4	90.8	3.6	74.1
10				176.8	2.6	268.0
12		1.2	1.8	48.6	14.4	287.6
13		10.0	129.4	13.0	2.8	117.2
17				143.0	5.4	23.8
18				44.5	1.6	53.1
20				43.4	2.4	81.4
21				103.0		146.8
22				1.1	0.4	38.2
31				235.6	2.4	46.2
32			3.0	232.2		131.4
33			0.4	163.6	2.0	46.8
34			3.2	171.2	1.6	328.8
35				24.0	14.4	230.6
36				2.1	3.6	33.5
MEAN		1.0	9.0	95.8	3.5	117.1

Table 3 shows the catch rates for the different types of pelagic fish in trawl stations from the inner and outer shelf including also hauls with pelagic trawl. There is a complete absence of anchovies on the outer shelf and also sardines are scarce here. Barracudas appear to be more abundant inshore and scombrids and carangids are more or less evenly distributed.

Atlantic sardinella, Sardinella aurita and thread herring, Opisthonema oglinum were the most common clupeids with American pellona, Pellone harroweri found less frequent. The sardinella was the only of these species found in any quantity on the outer shelf where it was caught together with scads and snapper in the bottom trawl.

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

INNER SHELF

STA. NO.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
1	36.8	89.6	32.0	16.0		1253.0
2	3.4	3.0	2.3	5.0		108.2
3	89.3	66.5	47.5			70.5
15	15.6	9.0	5.8	9.0	2.4	147.1
16	1.6	19.6	3.0	0.8		5.3
23	1320.0		6.6			67.4
24	0.9			9.0
25	15.6	10.2	67.0	3.4	1.8	570.6
26			14.0	8.0		14.0
27	253.8	761.2	1.8	5.4	47.6	413.2
28	0.6		16.2	0.8		47.4
29	496.8	1764.0	86.4	20.4	112.8	25.2
30	63.2	448.0	1057.0		136.8	1.2
37	283.0	8.0	5.0	1.2		33.0
38	38.4	230.4		43.6	4.8	514.0
39	232.0	208.0	56.0		147.2	1322.1
40			13.0	2.5	1.8	326.3
41	1.2	0.3	148.2		3.6	22.8
42	39.8	5.2	9.4	4.6		6.2
43	244.8	9.6	0.4			95.2
44	63.6	58.8		16.2		91.4
MEAN	152.4	175.7	74.84	6.9	21.8	244.4

OUTER SHELF

STA. NO.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
5	2.0		3.4	1.4		16.2
8	0.3		46.5		15.0	156.7
9			30.6	9.2	21.0	111.9
10			158.8			288.6
12	4.2		225.0		9.6	114.8
13	0.4		60.8	11.4	13.2	186.6
17			7.2			165.0
18			25.8	3.5	2.7	67.2
20			37.0	10.2	3.8	76.2
21	1.6		77.8	59.4		111.0
22	21.6		10.6	0.2	0.4	6.9
31	1.6		7.8	2.8		272.0
32	80.0		26.0		7.0	253.6
33	11.2		35.6			166.0
34	92.8		234.4			177.6
35	2.4		199.2			67.4
36	0.2		24.8			14.2
MEAN	12.8		71.2	5.7	4.2	132.4

Species of the genus Anchoa were by far the most common of the Engraulids, but also silver anchovy, Engraulis eurystole was caught in some quantities.

The rough scad, Trachurus lathami and the bigeye scad Selar crumenopthalmus were inhabitants of the outer shelf, while the bumper Chloroscombrus chrysurus occurred both inshore and offshore.

Of the two Spanish mackerels Scomberomorus maculatus was only caught on the inner shelf while S. regalis was found over the whole shelf.

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

Three hauls were made for deep sea shrimp at depths of 300-400m on the eastern Suriname slope, but with insignificant catches. Fishing conditions were, however, unfavourable with high currents and renewed attempts should be made under better conditions. Also shrimp catches on the outer shelf were low and few shrimp vessels were sighted.

Guyana

For records of fishing stations reference is made to Annex II from st. 45 on. For the purpose of the following faunistic analysis an overlap has been made and some stations made in Venezuelan waters have been included. Table 4 shows the standardized catch rates for the broad groups and for the inner and outer shelf. The higher catch rates for demersal fish and shrimp towards the northeast is evident. Table 5 present the catch rates by families of the demersal fish for the two parts of the shelf, and it is evident that croakers dominate the inner and snappers the outer shelf. The occurrence and mean catch rates of the main species were as follows:

Cynoscion virescens	found on 11 stations, mean:					70 kgs/hr
Cynoscion acoupa	“	“	10	“	“	36	“
Isopisthus parvipinnis	“	“	9	“	“	105	“
Macrodon ancylodon	“	“	18	“	“	101	“

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

INNER SHELF

STA. NO.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
46	69.6		25.6	100.0	3.2	105.8
47	81.4	4.8	0.8	1143.4		442.4
48	2.4	14.6		27.2
49	8.2	1.8		10.6	1.6	2.0
50				30.3	2.5	16.0
51	94.5	0.2	3.6	40.6		42.2
52	82.1	5.5	1.8	129.8	4.0	114.9
59	41.2	51.0	0.4	187.4	1.4	126.6
60	26.0			227.4		30.3
61	17.2	7.0	1.2	72.6	0.6	22.3
62	61.2		31.8	57.6		21.2
64	2.2		3.2	49.4	0.6	30.2
67	1.4			60.8	0.2
68	60.6	23.2	1.2	42.6	1.6	42.8
69	5.9		2.2	11.9		14.7
70	77.2		12.3	39.0	0.4	7.2
74	188.4	3.0		7.5		60.1
75	62.0		6.5	12.0		123.6
76	172.6	6.8	2.4	2.5		20.3
78	278.0	76.6	11.4	694.4		37.4
79	258.4	16.4	13.8
82	30.0		0.7			20.9
83	292.8	10.4	24.3	33.9		14.2
84	504.2	13.3	67.2			11.8
85	1503.8		462.0	385.0		35.2
86	929.8	18.2	348.0	48.0		170.6
87	406.0	9.2	3.4	52.8		257.7
88	60.8	4.8	0.7	17.4		34.5
MEAN	189.9	9.5	36.5	124.4	0.5	64.4

OUTER SHELF

STA. NO.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
53	22.6	10.6		19.6	7.8	9.4
54	86.1			1.4	2.3	3.1
55
56	67.6	2.6		459.0	5.4	69.8
57	124.2			132.2	3.0	46.0
58	1688.2			904.4	14.0	156.7
65				0.4	2.6	2.6
66	193.1	3.2		89.2		31.6
72	2.6			192.0	1.0	23.0
73	0.2			47.7		12.6
77	0.6	17.5		45.6	4.2	39.6
80	11.8			6.6	0.1	0.3
81	2.2	2.0	0.5		0.7	5.8
MEAN	169.1	2.7	0.0	146.0	3.1	30.8

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

INNER SHELF

STA. NO.	Catfish	Croakers	Snappers	Grunts	Groupers	Other
46	14.4	55.2				234.6
47	3.4	66.0	12.0	13.2		1578.2
48			2.4			41.8
49			8.2			16.0
50						48.8
51	0.2	94.0	0.2	1.6		85.1
52		41.5	40.6	40.5		215.5
59		41.2		10.8		356.1
60		19.6	6.4	12.5		245.2
61	3.90	13.3				103.7
62	7.80	53.4				110.6
64		1.8	0.4		0.4	83.0
67			1.4			61.0
68	2.0	57.0	1.6	8.2		103.2
69	1.1	4.8				28.8
70	1.6	75.6				58.9
74	65.6	122.8		8.5		62.1
75	31.8	30.2				142.1
76	35.0	137.6		1.0		31.0
78		278.0				819.8
79	20.6	237.8				30.2
82		20.5	9.5			21.6
83		292.8				82.8
84	21.4	482.8		4.0		88.3
85	25.6	1478.2		22.0		860.2
86	15.6	914.2				584.8
87	43.2	352.6	10.2	17.4		305.7
88	9.4	50.8	0.6	0.8		56.6
MEAN	10.8	175.7	3.3	5.0	0.0	230.57

OUTER SHELF

STA. NO.	Catfish	Croakers	Snappers	Grunts	Groupers	Other
53			22.6			47.4
54			86.1	1.10		5.7
55
56			67.6	10.80		526.0
57			124.2			181.2
58			1688.2		14.6	1060.5
65						5.6
66			193.1		20.4	103.6
72			2.6			216.0
73			0.2			60.3
77			0.6			106.9
80			11.8			7.0
81			2.2			9.0
MEAN			169.1	0.92	2.6	179.1

Red snapper followed by lane snapper was the most common of the large snappers, but the high catch rate of station 58 (1.6 t/hr) consisted of vermillion snapper, Rhomboplites aurorubens.

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

INNER SHELF

STA. NO.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
45	172.4	82.0	18.4	68.8	21.2	25.2
46	40.0	41.0		19.0		204.2
47	253.8	440.8	416.0	32.8	31.4	498.0
48			13.0	14.2		17.0
49	4.8	0.6	2.8	2.4		13.6
50	0.1		30.0	0.2	1.4	17.1
51	26.6		8.5	5.4	2.9	137.7
52	72.0	2.8	55.0		17.5	190.8
59	96.6	23.8	47.0	20.0	66.4	154.2
60	63.2	134.4.	26.2	3.6	8.0	48.3
61	25.0	39.6	5.2	2.8		48.3
62	9.6	48.0				114.2
63	3.4	102.6	2.4
64	1.8	0.0	47.6		5.2	31.0
67	18.6		34.6	7.6		1.6
68	6.0	28.8	1.6	6.2		129.4
69	3.9	7.0	1.0			22.8
70	22.8	14.0		2.2		97.1
71	21.3	124.0	32.3	14.2	6.6	61.1
74			7.5			251.5
75	2.4	9.6				192.1
76	0.4	2.0	0.1			202.1
78	529.2	8.0	83.6	73.6	10.6	392.8
79						288.6
82						51.6
83	31.2			2.7		341.7
84						596.5
85	6.6	308.0	70.4			2001.0
86	24.0	12.0	12.0			1466.6
87	35.4	8.0	9.4			676.3
88	15.2		2.2		3.0	97.8
MEAN	47.9	46.3	29.9	8.9	5.6	270.0

OUTER SHELF

STA. NO.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
53	0.7		4.9	14.0		50.4
54			1.4			91.5
55
56	144.0		315.0		32.4	113.0
57	11.4		119.2	1.6	6.2	167.0
58	11.8		879.6	13.0	13.8	1845.1
65			0.4		0.6	4.6
66	33.6		50.6	5.0		227.9
72	62.0		127.4	2.6	1.0	25.6
73	2.2		41.1	4.4	5.6	7.2
77			43.0	2.6	38.6	23.3
80	0.2		6.4		0.3	11.9
81					0.9	10.3
MEAN	20.4		122.2	3.3	7.6	198.3

The high catch rates for shrimp on stations 85 and 86 are partly due to the non-commercial species Nematopalaemon schmitti (176 and 312 kg/hr), partly to the seabob Xiphopenaeus kroyeri (286 and 36 kg/hr). In offshore waters pink - and brown shrimp Penaeus notialis and P. subtilis were caught and material was collected for studies of by catch both on inshore and offshore shrimp grounds.

Table 6 shows the catch rates for various types of pelagic fish inshore and offshore. Also here anchovies are absent offshore and sardines are scarce. The sardine species found in Suriname also occur in Guyana, but nowhere in high abundance. Anchoa spinifer dominated the anchovies and the scombrids included the king- and spotted Spanish mackerels. Among the Carangids the round scad Decapterus punctatus seemed to replace the rough scad in deeper waters and both bluntnose jack and bigeye scad were common. Two species of barracudas were caught, Sphyraena guachancho and S. picudilla.

Annex IV shows pooled size distributions of samples of the main species caught.

Venezuela and the Joint Fishing Area south of Trinidad

Time did not permit an adequate coverage and sampling of all of this area and more detailed work should be done in the coming surveys particularly in the area south of Trinidad and north of Venezuela. For purposes of analysis an overlap has been made with fishing stations outside the eastern part of the Orinoco Delta. All fishing on this lag was done on the inner shelf down to 65m of depth. Table 7 shows the standardized catch rates in bottom trawl by the broad groups. Some large catches were obtained and Table 8 shows that these were caused by high rates of croakers. The occurrence and mean catch rates for the various species of this group were:

Cynoscion virescens	found on 11 stations, mean:					81 kgs/hr
Cynoscion acoupa	“	“	8	“	“	13	“
Isopisthus parvipinnis	“	“	12	“	“	86	“
Macrodon ancylodon	“	“	13	“	“	123	“

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

STA. NO.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
83	292.8	10.4	24.3	31.2		16.9
84	504.2	13.3	67.2			11.8
85	1503.8		462.0	396.0		24.2
86	929.8	18.2	348.0	216.0		2.6
87	406.0	9.2	3.4	279.2		31.3
88	60.8	4.8	0.7	31.8		20.1
89	26.1	0.6	21.3	13.2		3.9
90	84.6		35.2	45.0		33.7
91	191.7	5.6	2.0	69.0		9.8
92	187.4	6.9	45.3	159.0		10.6
94	85.0	8.7	4.2	80.4	1.2	5.9
95	275.4	5.4	15.6	281.7		54.7
96	234.4	6.1.	19.8	133.4		90.6
98	109.4	17.2	2.8	261.8		32.0
MEAN	349.3	7.6	75.1	142.6	0.0	24.8

The main species of catfish caught were Arius grandicassus and Bagre bagre.

The high rates of shrimp on stations 85 and 86 are explained under Guyana above. The other shrimp catches were brown and pink shrimp from the offshore grounds fished by a shrimp fleet and seabob inshore. Data for by-catch assessments were obtained.

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

STA. NO.	Catfish	Croakers	Snappers	Grunts	Groupers	Other
83		292.8				82.8
84	21.4	482.8		4.0		88.3
85	25.6	1478.2		22.0		860.2
86	15.6	914.2				584.8
87	43.2	352.6	10.2	17.4		305.7
88	9.4	50.8	0.6	0.8		56.6
89		26.1			0.3	38.7
90		64.6	20.0			113.9
91	2.0	188.6	1.1			86.4
92	38.6	148.8				221.8
94	8.8	75.6	0.6			100.4
95	56.4	219.0		3.6		353.8
96	72.6	161.8			1.4	248.5
98	18.8	90.6				313.8
MEAN	22.3	324.7	2.3	3.4	0.1	246.8

Table 9 shows catch rates for pelagic fish by families in bottom and mid water hauls. The sardines were represented by thread herring, pellona and scaled herring, the anchovies mostly by Anchoa spinifer, A. hepsetus and Cetengraulis edentulus and the Carangids by bluntnose jack and lookdowns. Hairtails formed an important part of many catches.

The size composition of some of the common species are shown in Annex V.

Table 9. VENEZUELA. Catch rates by families for pelagic fish In pelagic and bottom trawl hauls, kg/hour.

STA. NO.	Sardines	Anchovies	Carangids	Scombrids	Hairtails	Other
83	31.2			2.7		341.7
84						596.5
85	6.6	308.0	70.4		11.0	1990.0
86	24.0	12.0	12.0		168.0	1298.6
87	35.4	8.0	9.4		226.4	449.9
88	15.2		2.2		14.4	86.4
89	3.0				10.2	51.9
90	36.8		0.8		7.4	153.5
91	22.4	6.6			40.0	209.1
92		2.2	60.8		96.0	250.2
94	36.0	8.4	1.2		34.8	105.0
95	57.6	180.0	8.1	11.6	36.0	339.5
96	16.8	24.0	18.2	9.2	74.4	341.7
98	78.4	95.2	9.2	10.2	79.0	151.2
100	4.0	37.5	2.2	1.7		3.5
102	114.0	212.0	0.4	1.6	8.0	8.8
MEAN	30.0	55.8	12.1	2.3	50.3	398.6