3.2 GUYANA

3.2.1 Small pelagic fish
3.2.2 Demersal resources
3.2.3 Overview and discussion of survey results

Figure 3.1.1 shows the course tracks and fishing stations in the area.

Introduction

Reference is made to the general description of the Guiana shelf, its hydrography and fish assemblages under chapter 2 above. In the south-east the Guyana shelf represents an extention of the 80-90 nm broad and gently sloping Suriname shelf. However, from the Essequibo River westwards, the Guyana shelf narrows to some 40 nm and the even slope is in some parts disrupted by offshore shallow banks. This bottom configuration affects the hydrographic conditions by preventing the intermediate upwelled water from reaching inshore. These inshore parts may thus be less productive than in Suriname. The fish fauna in the south-east may most appropriately be considered part of joint Suriname-Guyana stocks, while that of the north-western shelf represents a Guyana proper fauna or a transitions to the Orinoco system.

3.2.1 Small pelagic fish

Fish distribution

The extention of the dense inshore aggregations from Suriname into the south-east Guyana shelf is clearly demonstrated in the distribution charts from surveys 1, 2, and 4, Figure 3.1.2. Dense aggregations were scarce west of the Essequibo River except in November when a concentration of juvenile anchovies and sardines were located here.

The acoustic distribution charts thus show a main pattern of distribution of pelagic fish similar to that found in Suriname, but clearly more restricted and with less overall abundance.

Catch compositions

The mean catch rates by groups and surveys, see Tables 3.2.1 and 3.2.2 are as expected roughly similar to those from Suriname. The mean rates for the main groups are, however, lower and the drops in the August survey rates are less pronounced. The carangids show relatively high abundance on the outer shelf and the large sized predators on the inner shelf.

Table 3.2.3 shows the composition by main species within families using the mean proportion by weight of all catches compiled for each survey. The Anchoa genus dominate the engraulids with Anchoviella about half as abundant. More than half the clupeid catches were sardinella and thread herring with scaled herring and pellona accounting for 1/3. Bumper and bluntose jacks were the most abundant carangids with round scad and lookdowns next. This species composition differs somewhat from that off Suriname with less lookdowns and rough scad.

Table 3.2.1 Guyana. Pelagic fish. Inner shelf. Catch rates in kg/hour by main groups by surveys. Mean rate, three highest rates and rate of occurrence.

Survey	Mean rate	Highest rates			Rate of occurrence
ENGRAULIDS
1 Jan.-Febr.	46	440,	308,	134	20/31
2 May	41	684,	154,	116	15/33
3 August	28	172,	120,	103	13/27
4 November	30	225,	202,	182	18/32
CLUPEIDS
1 Jan.-Febr.	48	529,	253,	172	26/31
2 May	45	540,	247,	65	24/33
3 August	31	221,	123,	106	23/27
4 November	44	457,	152,	137	26/32
CARANGIDS
1 Jan.-Febr.	30	416,	84,	70	23/31
2 May	34	168,	146,	128	31/33
3 August	38	382,	173,	86	24/27
4 November	28	175,	106,	95	30/32
SCOMBRIDS
1 Jan.-Febr.	9	69,	32,	20	16/31
2 May	17	312,	37,	27	19/33
3 August	12	81,	50,	48	14/27
4 November	21	225,	70,	54	25/32
BARRACUDAS
1 Jan.-Febr.	6	66,	31,	21	11/31
2 May	3	27,	18,	14	13/33
3 August	10	106,	62,	43	12/27
4 November	16	144,	104,	90	15/32
HAIRTAILS
1 Jan.-Febr.	12	222,	28,	26	14/31
2 May	14	147,	64,	63	14/33
3 August	16	112,	62,	60	13/27
4 November	16	140,	80,	64	14/32

Table 3.2.2 Guyana. Pelagic fish. Outer shelf. Catch rates in kg/hour by main groups by surveys. Mean rate, three highest rates and rate of occurrence.

Survey	Mean rate	Highest rates			Rate of occurrence
CLUPEIDS
1 Jan.-Febr.	20	144,	62,	34	8/13
2 May	1	2,	1,	0	3/12
3 August	93	894,	128,	2	5/11
4 November	35	410,	3,	1	5/12
CARANGIDS
1 Jan.-Febr	122	880,	315,	127	11/13
2 May	8	50,	12,	8	10/12
3 August	30	269,	48,	4	10/11
4 November	20	103,	51,	35	9/12
SCOMBRIDS
1 Jan.-Febr.	3	14,	13,	5	7/13
2 May	1	2,	1,	0	2/12
3 August	2	10,	7,	5	4/11
4 November	2	17,	6,	3	3/12
BARRACUDAS
1 Jan.-Febr.	8	39,	32,	14	9/13
2 May	1	2,	1,	1	3/12
3 August	1	6,	6,	0	2/11
4 November	1	10,	3,	0	2/12

Table 3.2.3 Guyana. Species distribution by families of small pelagic fish. Catch by weight of species by surveys as per cent of total catch of family.

Survey:	1	2	3	4	Mean
ENGRAULIDS
Mean catch, kg/hour	46	41	28	30
Anchoa spp.	95	15	99	25	59
Anchoviella spp.		59		61	30
Engraulis spp.	4			12	4
CLUPEIDS
Mean catch, kg/hour	41	32	44	43
Opisthonema oglinum	10	11	14	12	12
Sardinella aurita	26	38	53	51	42
Pellona harroweri	26	21	7	12	17
Chirocentrodon bleekerianus	12	6	10	6	9
Harengula jaguana	24	21	14	5	16
Odontognathus spp.				11	3
CARANGIDS
Mean catch, kg/hour	60	28	36	26
Chloroscombrus chrysurus	23	38	45	44	38
Selene spp.	3	9	13	13	10
Trachurus lathami	9	2	1	5	4
Hemicaranx amblyrhyncus	14	31	8	21	19
Selar crumenophthalmus	9	11	14	3	9
Decapterus punctatus	39	3	9		13
Trachinotus spp.				5	1
Oligoplites spp.			4	5	2
Caranx spp.		4	5		2

Biomass estimates

The estimates of biomass based on the acoustic observations are shown in Table 3.2.4. They are fairly consistent at about 300 000 tonnes for survey 1, 2 and 4, but only about 1/3 of that for the August survey. As for Suriname we propose to disregard this season of low availability in the calculation of standing biomass which then gives a total of 300 000 tonnes of which 160 000 tonnes engraulids and clupeids and 140 000 tonnes carangids etc.

Table 3.2.4 Guyana. Estimates of standing biomass of pelagic fish by surveys and groups. 1 000 tonnes.

Survey	Pelagic 1	Pelagic 2	Total
1 Jan.-Febr.	140	150	290
2 May	150	170	320
3 August	80	30	110
4 November	190	110	300

A further rough breakdown of these group estimates may be obtained also here by use of the proportions of the total catches between families and for the surveys 1, 2 and 4. The results of such calculations are as follows:

Engraulids	55 000	tonnes
Clupeids	105 000	tonnes
Carangids	80 000	tonnes
Scombrids	25 000	tonnes
Barracudas	15 000	tonnes
Hairtails	20 000	tonnes

The proportion between engraulids and clupeids is similar to that found in Suriname, but the carangids and scombrids are relatively more abundant in Guyana.

If as discussed above the more solitary scombrids and barracudas have a higher catch-ability than the true schooling pelagic forms their biomass is overestimated here. Swept area estimates of their biomass give 5 000 tonnes and 3 000 tonnes respectively for these two groups and 5 000 tonnes for hairtails. The somewhat arbitrary approach of using the means of the two sets of estimates gives stock biomasses of 15 000 tonnes of Spanish mackerels and 9 000 tonnes of barracudas and 12 000 tonnes of hairtails.

3.2.2 Demersal resources

The data for the swept area analysis and catch composition of demersal fish comprise 38, 38, 29 and 45 trawl hauls from the respective four surveys. In the analysis the data-sets from the shelf have been analysed by two depth strata: 0-50 m and 50-120 m, termed the inner and outer shelf. The deep slope off Guiana is narrow and with few locations suitable for bottom trawling. Only one haul was carried out on the slope. Below, only the highlights from the analysis with the main species or species groups will be commented upon in the text. The complete results from the analysis are included in Annex 7 of the DATA FILES.

The demersal fish fauna off Guyana has a high similarity to that off Suriname, but with a shift in the relative importance of the various groups. The outer shelf is still dominated by snappers, but in lower densities compared to Suriname. The division between an inner and outer shelf is less apparent as the snappers seem to have migrated closer to shore during the third survey. This species group has its main distribution on the eastern part of the Guiana shelf. The croakers are the dominating group in the nearshore areas, and even extended their distribution beyond 50 m bottom depth during the first survey (February). The scope of this report does not permit a detailed analysis of the distribution on the level of the species. The national research laboratories in the region should be encouraged to undertake such studies on basis of the material collected. The studies should incorporate the whole region as several stocks are common between neighbouring countries.

Demersal fish

The main species on the inner shelf are king weakfish (Macrodon ancylodon), southern red snapper (Lutjanus purpureus), green weakfish (Cynoscion virescens) and shortfin corvina (Isopisthus parvipinnis) in order of importance in the data from all surveys pooled. The material show considerable seasonal fluctuations in species composition. Common but at low densities are lane snapper (L. synagris), American harvestfish (Peprilus paru) and silver mojarra (Eucinostomus argenteus). On the outer shelf the dominating species are vermillion snapper (Rhomboplites aurorubens), cardinal snapper (Pristipomoides macrophthalmus) and acoupa weakfish (Cynoscion acoupa). Bigeye (Priacanthus arenatus) was common in the catches, but with lower catch rates. As mentioned under Suriname above these stocks must according to their distributional pattern to some extent be considered as joint resources with Suriname.

Catch composition

As most of the bottom trawl hauls are randomly localized for purpose of swept area estimates, they will not be representative for an aimed fishery at targeted species and locations. The highest catches, however, might be representative for a fishery, and the mean catch might serve as indicators of minimum catch rates in a wide scale multi-species fishery.

Table 3.2.5 shows the mean catch rates in kg/hour and the catch distribution by size classes for the main species of demersal fish off Guyana for all surveys pooled. For the inner shelf the mean catch for the dominating species fall within the 10 to 30 kg/hour range, while in the outer shelf they are within the 7 to 12 kg/hour range. Table 3.2.6 shows the catch rates summed by species groups. For the inner shelf the dominating group is the croakers with a mean rate of 74 kg/hour, followed by snappers (33 kg/hour) and grunts (12 kg/hour). For the outer shelf the dominating group is the snappers with a mean rate of 33 kg/hour succeeded by croakers (20 kg/hour). The snappers, groupers croakers and grunts sum to a mean rate of 120 kg/hour for the inner shelf and 60 kg/hour for the outer. Other demersal fish, mainly non-commercial, amount to about 40 and 30 kg/hour for the inner and outer shelf respectively.

Table 3.2.5 Guyana. Mean catch rates and catch distribution by size classes for all swept-area hauls on the shelf.

Species		Mean rate	Number of hauls in catch groups						Rate of occurrence*
		kg/hour	1-30 kg	30-100 kg	0.1-03 t	0.3-1 t	1-3 t	>3 t
INNER SHELF
	King weakfish	27	27	16	7	2			52/153
	Vermillion snapper	18	38	7	2		1		48/153
	Southern red snapper	10	51	4	1	1			57/153
	Green weakfish	10	20	7	2	1			30/153
	Shortfin corvina	9	25	3	1	1			30/153
OUTER SHELF
	Vermillion snapper	12
	Southern red snapper	9
	Cardinal snapper	8	32	3					35/153
	Acoupa weakfish	7	14	1	1				16/153

* calculated on basis all hauls total shelf.

Family	INNER SHELF	OUTER SHELF
Snappers	33	33
Groupers	2	2
Croakers	74	20
Grunts	12	4

Biomass estimates

Estimates offish density by depth strata are given in Annex 7. By multiplying these densities with the area of the shelf, given in Table 2.3.1 estimates of standing biomass are obtained by surveys and species or species groups. Such estimates are presented in Table 3.2.7, summarized by the main species groups.

Table 3.2.7 Guyana. Estimates of biomass of demersal fish on the shelf by main group and surveys.

		Survey 1	Survey 2	Survey 3	Survey 4	All surveys
INNER SHELF
	Snappers	27 000	14 500	3 500	5 000	11 000
	Croakers	50 000	16 500	15 000	25 000	25 000
	Grunts	1 500	1 000	10 000	7 000	4 000
	Groupers	500	0	500	500	500
	Other demersal	24 000	20 000	15 000	14 500	18 000
OUTER SHELF
	Snappers	3 000	2 000	3 000	8 000	4 000
	Croakers	8 000	0	0		2 500
	Grunts	100	100	0	4 000	400
	Groupers	0	800	0	0	300
	Other demersal	3 000	2 000	4 500	5 000	3 500
	Total, main groups	90 000	35 000	32 000	49 000	47 000
	Total, other dem.	27 000	22 000	20 000	20 000	22 000

There is a considerable variation in the estimates between surveys for snappers, croakers and grunts. This is partly due to migration taking place between the surveys, but the main cause is probably sampling variance due to the patchy distribution of the species. The total estimates from all surveys are less influenced by sampling variance and are considered more reliable.

The snappers have an estimated total biomass of about 15 000 tonnes, with about 1/3 in the outer shelf waters. The croakers make up about 25 000 tonnes confined to the inner shelf during three surveys, with a few thousand tonnes more offshore during one survey only (February). The biomass of grunts is of the order 4 000 tonnes and groupers less than 1 000 tonnes, mostly confined to the inner shelf. Other demersal fish, mostly of minor or no economic importance, amounts to roughly 20 000 tonnes, with about 85% of it in the inner shelf waters.

Sharks

Table 3.2.8 shows the shark catch data by surveys. Both catch rates and incidence are somewhat lower than in Suriname demonstrating lower abundance of this group. Swept area estimates give a biomass of 3 000 tonnes, which must, however, be regarded as an underestimate.

As shown by Table 3.2.9 the Caribbean sharpnose was by far the most common of the shark species while the blacknose Carcharhinus acronotus dominated the requiem sharks and the bonnethead Sphyrna tiburo the hammerheads. The restricted availability is demonstrated by the low rates of incidence except for the Caribbean sharpnose shark with 26%. The sizes were also here generally small.

Table 3.2.8 Guyana. Sharks. Catch rates in kg/hour by main groups by surveys. Mean rate, three highest rates and rate of occurrence.

Survey	Mean rate	Highest rates			Rate of occurrence
1 Jan.-Febr.	7	77,	51,	23	21/41
2 May	4	34,	29,	28	14/44
3 August	3	56,	24,	12	10/36
4 November	8	99,	56,	44	16/40

Table 3.2.9 Guyana. Sharks. Proportion by weight in catch, range of sizes and percentage occurrence in all catches.

		Catch %	Range of size, kg.	Incidence %
Requiem sharks,	Carcharhinus spp.	11	3 - 6	1 - 3
Sharpnose sh.,	Rhizoprionodon spp.	71	0.3 - 3	1 - 26
Hammerheads,	Sphyrna spp.	15	1 - 5	3 - 7
Smooth-hounds,	Mustelus spp.	3		1 - 5

Squid

The distribution of squid on the Guyana shelf extended somewhat deeper than in Suriname, but the major part was found inside the 50 m depth line. Table 3.2.10 shows the catch data for the inner shelf. Rates are generally low with a few modest catches. The distribution was patchy and special “squid grounds” may exist.

Table 3.2.10 Guyana. Squid Inner shelf. Catch rates in kg/hour by main groups by surveys. Mean rate for all hauls and where present, three highest rates and rate of occurrence.

Survey	Mean rate		Highest rates			Rate of occurrence
	All	Where pres.
1 January	1	2	4,	3	2	8/28
2 May	6	13	46,	31,	26	15/32
3 August	1	5	6,	4,	1	5/25
4 Oct.-Nov.	8	14	97,	28,	26	16/28

The dominating species was Loligo plei. Sizes ranged up to 15 cm mantel length, but in August only to 10 cm. A swept area estimate give a mean standing biomass of 1 700 tonnes which is likely to be an underestimate of the stock size.

Shrimps

Suitable grounds for deep sea shrimp trawling seems limited off Guyana, but no great effort was spent in searching for trawl ground beyond 400 m depth. A single test at some 700 m confirmed the availability of the deep water scarlet shrimp Plesiopenaeus edwardsianus at this depth as in Suriname and Orinoco, but with low catch rate.

The data on shallow water shrimps are as discussed under Suriname above only of limited value. Table 3.2.11 shows the summarized catch data for the hauls where present. The brown shrimp was most common with highest rates in January-February and in August. The modal size was lowest in August and November. The red spotted and pink shrimps showed highest catch rates at night. Some of the data could serve as a basis for an analysis of fish by-catch in the shrimp fisheries.

Table 3.2.11 Guyana. Shallow water shrimps. Mean catch rates in hauls where present and highest rates by surveys, mean rates for all surveys and by day/night, kgs/hour. Total catch adjusted to a standard survey effort for all surveys.

	Brown	Red spotted	White	Pink
1 Jan.-Febr.	5 (20)	1 (2)	1	3 (4)
2 May	2 (4)	3 (3)	3 (6)	2 (4)
3 August	5 (13)	3 (5)		1 (3)
4 November	2 (3)	1 (1)		2 (3)
All surveys	4	2	1	1
All surveys day	3.7	0.4	1.2	0.9
All surveys night	2.9	1.9	0	1.5
Adjusted catch	104 kgs	76 kgs		61 kgs

3.2.3 Overview and discussion of survey results

The following groups of resources were identified and will be discussed:

Small pelagic fish was found mainly in dense inshore aggregations which extended from the Suriname into the south-east Guyana shelf, but with low densities west of the Essequibo River. The catch composition by groups were roughly as in Suriname, clupeids, anchovies, and carangids with some pelagic predators, but with lower mean catch rates.

Demersal fish was found in highest abundance on the inner shelf with a dominance of croakers, but also with some abundance of snappers and grunts.

Sharks appeared in the catches mainly on the inner shelf, but with low mean rates.

Shrimps. Only incidental observations are presented on the important resources of shallow water shrimps.

Squid was found in modest amounts in the mid shelf consisting mainly of small Loligo species, some times with a patchy distribution.

Table 3.2.12 shows a summary of the assessments of the standing stock of the various groups. Some of these are likely to be especially biased towards an underestimate such as those for sharks and perhaps the red snapper. With a total biomass of 370 000 tonnes and a shelf area of 13 900 nm² the mean density of biomass of the Guyana shelf is 27 t/nm² which indicates a moderate productivity. The total biomass may as discussed above be underestimated, but the density is markedly lower than that found in Suriname. A part of the difference could be caused by a higher rate of exploitation in Guyana.

Table 3.2.12 Guyana. Summary of estimates of standing stock biomass. Tonnes.

Pelagic fish
	Engraulids	55 000
	Clupeids	105 000
	Carangids	104 000
	Scombrids	15 000
	Barracudas	9 000
	Hairtails	12 000
	Total		300 000
Demersal fish
	Snappers	15 000
	Grunts	4 400
	Croakers	27 500
	Groupers	800
	Other demersal mostly non-com.	21 500	69 000
Sharks			3 000
Squid			2 000
Shallow water shrimp
Total			370 000

Some data are available on the findings from a previous trawl surveys of the Guyana shelf. In Table 3.2.13 the results for each survey have been converted to the use of the same catchability coefficient as that applied for the results from “DR. FRIDTJOF NANSEN” viz. q = 1. There is seen to be a considerable similarity between the standing stock estimates for the inner shelf.

Table 3.2.13 Guyana. Comparison of estimates of standing biomass from various surveys with calculations adjusted to a catchability coefficient q = 1, tonnes, and ratios fish density Suriname/Guyana. Sources: Klima (1976) and Fabres (1980).

Survey:	Inner shelf	Outer shelf	Total	Ratios
Calamar (1967-68)	84 000			1.74
La Salle (1969)	60 300			1.55
Oregon II (1972-77)		37 000		1.17
Dr Fridtjof Nansen	76 500	10 700	87 000	1.67	2.05

The ratios of mean fish density between the inner shelf hauls off Suriname and those off Guyana in the various surveys are also all showing a similar and significantly lower level in Guyana. The low standing stock found in our survey in the outer part of the Guyana shelf as compared to the “OREGON II” 1972-77 results may demonstrate a stock decline brought about by fishing. A comparison with the findings of a commercial survey with the GDR freezer trawler “ORKNEY” (Anon 1980) showed that the catch composition obtained in our survey was largely the same as that of the GDR operation and mean catch rates were roughly similar.

The fishery statistics of Guyana show that the total landing of finfish has increased from about 30 000 tonnes around 1980 to about 40 000 tonnes during 1984-87. Some 10% is landed from industrial vessels, the rest is fished by a large and mostly well equipped fleet of artisanal boats operating mostly in the inner shelf. The catch include croakers, catfishes, grunts, Spanish mackerels, carangids, sharks and snappers, source Chakalall and Dragovich 1983. When comparing this total catch with the level of standing biomass of the relevant stocks it seems clear that they must in general be exploited at a significant level. Assuming a total mortality of 0.7 and a fishable biomass of 130 000 tonnes which includes the commercial groups of the demersal fish, scombrids, barracudas, hairtails, sharks and about half the carangids, the estimate of the potential long term yield is 45 000 tonnes. This is a rough indication that most of the fin-fish stocks are fully utilized. A more detailed analysis should be made with catch statistics by species and other data and this would probably demonstrate some unused potentials for some stocks. The remaining about 200 000 tonnes biomass of anchovies, sardines and smaller carangids may be exposed to some exploitation as a by-catch in the shrimp fisheries.