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. 299 - 338. 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. 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. Sharks and squid showed highest catch rates on the inner shelf. The squids, Loligo palaei and L. plei were markedly more abundant than in Survey I and the highest catch rates were obtained during daytime in 25 - 35 m depth. In general only low catch rates of shrimps were obtained except for st. 308 which represents the standardized rates of a 12 min haul (stuck in mud) with catches of 144 kg of seabob and 48 kg of P. subtilis.

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
306	40	3.00			17.00	2.80	2.00
307	32	303.80	86.40		1054.80		7.20
308	20	625.00		960.00	532.50		160,00
309	11	47.60		29.60	107.80		4.80
310	18	57.60		24.00	168.40		30.80
312	34	105.60		1.60	142.80		114.60
321	30	7.40		4.60	3.40	4.00	36.80
322	27	285.40	105.60		2396.20		68.40
323	31	2.00			286.00	95.00
324	27				36.90	84.00	0.80
325	16		17.40		20.00		21.20
326	24	6.30	4.20		95.10	18.00	4.10
327	32	150.94			1833.94	29.44
328	20	3.60	4.60		177.20		31.00
329	24	113.10	5.40		182.80	9.00	10.20
330	30	38.20		3.00	29.20		263.20
331	28	60.80		0.80	16.00	1.60	29.60
335	37	1.60			7.60	5.00	0.70
336	28	12.00			187.20	42.00	132.00
337	26	1726.80			242.40	12.60	18.20
MEAN		177.54	11.18	51.18	376.86	15.17	46.78

OUTER SHELF

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
299	81	25.10	13.64		22.09	0.27	9.02
300	86				199.80	0.90	1.20
301	115	40.20			59.00
302	91	151.00			212.80		7.20
303	77		11.00		32.80		1.20
304	92	0.60	30.00		73.40		66.00
305	56				0.10		0.10
313	83	185.80	25.40		199.60		6.00
314	78	34.56	1.68		33.24		1.20
315	80	12.80			252.00	4.00	8.40
316	72	235.60			121.80	1.40	80.20
317	82	230.40			499.20		50.40
318	65	493.80			185.40	5.40	3.60
319	50	143.20			319.90	1.40	19.60
332	81	38.55				3.90
333	59	1.50	9.40			2.80	1.50
334	48	36.60			309.00		16.20
MEAN		95.87	5.36		148.24	1.18	15.99

Table 2 presents an analysis of catch rates by families of demersal fish for the two parts of the shelf. The predominance of catfish, croakers and grunts on the inner shelf and of snapper on the outer part is evident. The lane snapper Lutjanus synagris formed an important part of the catches in the 25 - 40 m depth zone. The species in the inshore assemblage were largely the same as those found in Survey I: king - and green weakfishes, Macrodon ancylodon and Cynoscion virescens dominated among the croakers, the corocoro - and bronzestriped grunts Orthopristes ruber and Haemulon boschme among the grunts and the white catfish Bagre bagre was the most common of that family. On the outer shelf the red snapper Lutjanus purpureus occurred with limited catch rates while the small size vermillion snapper Rhomboplites aurorubens was generally more abundant. The catch rates for the various groups are largely similar to those obtained in Survey I although there are some differences in mean rates mainly caused by a few very high rates obtained in that survey.

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

INNER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
306	40					3.00	21.80
307	32		126.00	122.40		55.40	1148.40
308	20	180.00	445.00				1652.50
309	11	0.40	47.20				142.20
310	18	5.60	52.00				223.20
312	34		28.80	34.20	2.40	40.20	259.00
321	30			2.80	0.20	4.40	48.80
322	27	58.60	187.20	17.60		22.00	2570.20
323	31				1.00	1.00	381.00
324	27						121.70
325	16						58.60
326	24		0.30	5.40		0.60	121.40
327	32			9.75		141.19	1863.38
328	20	3.60					212.80
329	24		2.10	10.20		100.80	207.40
330	30		31.60	6.60			295.40
331	28			30.40	4.40	26.00	48.00
335	37					1.60	13.30
336	28			3.60		8.40	361.20
337	26			11.80		1715.00	273.20
MEAN		12.41	46.01	12.74	0.40	105.98	501.17

OUTER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
299	81		2.73		0.55	21.82	45.02
300	86						201.90
301	115					40.20	59.00
302	91					151.00	220.00
303	77						45.00
304	92					0.60	169.40
305	56						0.20
313	83				35.00	150.80	231.00
314	78					34.56	36. 12
315	80					12.80	264.40
316	72				40.60	195.00	203.40
317	82					230.40	549.60
318	65			32.40	20.00	441.40	194.40
319	50			30.80		112.40	340.90
332	81					38.55	3.90
333	59					1.50	13.70
334	48					36.60	325.20
MEAN			0.16	3.72	5.66	86.33	170.77

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	Anchovies	Carangids	Scombrids	Barracudas	Other
306	40	6.60		8.60	0.40		9.20
307	32	536.40			82.80	54.00	779.00
308	20		512.00	12.50	8.00		1745.00
309	11	5.00	34.80	30.40	28.80		90.80
310	18	6.40	146.40	0.80	2.80		124.40
311		136.80	67.20	12.00			68.00
312	34	9.00		132.00		1.80	221.80
320	10	618.00		31.00			8.00
321	30			2.80		0.60	52.80
322	27	1369.00		49.20	73.20		1364.20
323	31		32.00	234.00			117.00
324	27	10.00		1.90	25.00		84.80
325	16		9.00	5.00	6.00		38.60
326	24	7.20	70.40	2.00	2.10	0.60	45.40
327	32	6.56		948.19	68.81	810.38	180.38
328	20	5.20	26.00	38.40	25.60	3.60	117.60
329	24	101.40	22.20	8.40	17.00	18.80	152.70
330	30			21.60		7.60	304.40
331	28	11.20		4.00		0.80	92.80
335	37	1.50		6.10			7.30
336	28	1.20		180.00	6.00		186.00
337	26	17.60		39.80	185.00		1757.60
338		104.00	132.80	12.00	46.60		51.40
MEAN		128.39	45.77	77.42	25.14	39.05	330.40

OUTER SHELF

ST. NO.	DEP.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
299	81			16.36		5.18	48.58
300	86	4.80		180.00		15.00	2.10
301	115	2.20		56.80			40.20
302	91	0.80		212.00			158.20
303	77			19.80	10.60		14.60
304	92			44.60	14.00		111.40
305	56			0.10			0.10
313	83			146.00	46.60	2.00	222.20
314	78	0.72		22.92	6.00		41.04
315	80	56.00		194.40	1.60		25.20
316	72			30.80		91.00	317.20
317	82			499.20			280.80
318	65	135.00		50.40			502.80
319	50			235.90	84.00		164.20
332	81						42.45
333	59						15.20
334	48	82.40		215.60		11.00	52.80
MEAN		16.58		113.23	9.58	7.30	119.95

There is as previously an absence of anchovies on the outer shelf and also sardines are scarce here, the family being represented only by Atlantic sardinella, Sardinella aurita. Most of the carangid catches in deep water consisted of rough scad, Trachurus lathami and bigeye scad Selar crumenopthalmus.

On the inner shelf anchovies appeared to be less common and abundant than in Survey I. Sardines were well represented with thread herring, Opisthonema oglinum as the most common form, but a number of catches of scaled herring, Harengula jaguana, American pellona Pellone harroweri and dogtooth herring Chirocentrodon bleekerianus were also made.

The bumper Chloroscombrus chrysurus was common inshore with some Decapterus sp.

The catch rates for Spanish mackerels and barracudas were higher than in survey I. The spotted type Scomberomorus maculatus was the most common form.

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. 339 on. For the purpose of the following 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 (shallower resp deeper than 60 m). All groups show low catch rates offshore. Squids show highest rates in the east and sharks in the inshore western part. The catch rates for all these groups except squid are considerably lower than in Survey I. For squid the rates are markedly higher in this survey.

The relatively high rates for shrimp in some of the shallow water hauls derive from Nematopalaemon schmitti and Xiphopenaeus kroyeri. Catch rates for the large sized Penaeid shrimps were low, up to 10 kg/hour and included the pink, white and red spotted species. In general these rates were down from Survey I.

Table 5 presents the catch rates by families for demersal fish on the inner and outer parts of the shelf. As previously catfish and croakers dominate the inner - and snappers with some groupers the outer shelf. The king weakfish Macrodon ancylodon dominate the croakers with some green - Cynoscion virescens and Jamaica weakfish Cynoscion jamaicensis. The red snapper Lutjanus purpureus was the most common of this family and in contrast to further east it occurred up to abt. 40 m of depth.

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
339	20	160.00	1.60	76.80	40.00		116.80
340	27	1.00			18.30	31.00	6.60
341	28				106.40	26.00	1.40
342	23	31.20			98.80	15.20	4.40
343	19		12.00		219.60		207.60
344	24	9.60	1.60		358.40	46.40	56.00
345	25	2.80		3.40	97.20	20.00	32.80
349	49	70.20			2.20	2.20	17.60
350	45	134.00	1.00		21.20	1.00	53.00
351	27				164.00	18.00	2.50
352	22	2.00		0.60	35.60	5.00	19.30
354	24	130.90		1.00	98.40		33.50
355	22			1.20	64.80	0.60	10.80
356	17	380.60	28.00	43.40	130.20		309.60
357	22	16.00			335.00		40.00
358	15	219.01		113.54	25.39		11.76
360	23	103.21		1.03	283.79
361	42	1.20		1.00	22.60	2.20	10.80
362	56				1.20	7.00	2.80
363	44	0.20			212.40	8.00	0.60
364	39	982.40			167.20		88.00
365	37	3.80		0.60	71.30	0.60	0.60
366	35	66.80	2.00	3.40	114.20		87.40
369	15	162.20		28.00	101.00		159.20
370	29	8.00	1.40		759.60		7.20
371	18	288.40	28.20	12.00	136.00		112.00
372	57				62.60	1.20	0.80
375	11	163.40		18.00	238.20		53.00
376	52	3.80	33.80		45.90		0.70
377	30	1.10			33.90		0.50
378	14	7.40	28.80	3.60	228.00		22.40
379	43		11.40		45.30		1.20
MEAN		92.16	4.68	9.61	135.58	5.76	45.96

OUTER SHELF

ST. NO.	DEP.	Demersal	Sharks	Shrimp	Pelagic	Squid	Other
346	72	33.80			8.20	4.00	1.00
347	61	2.90			0.10	3.00	1.80
348	77	17.50			51.44	2.10	44.10
367	68	74.40		3.20	0.40	0.80	34.40
368	66	34.00		5.40		0.80	56.00
373	81	2.40			12.20	1.40	11.20
374	84	105.00			6.60		7.80
380	61		1.40	1.00	7.60	4.80	42.20
381	76	79.60			8.90	2.80	4.40
382	76	88.50		4.80	1.80	0.60	55.50
383	82	140.80	5.60	5.60		3.20	78.80
384	68	19.20	2.00	9.00	11.00	5.60	52.60
MEAN		51.41	0.83	3.27	9.34	2.63	35.65

Table 6 presents the catch rates analysed by families of pelagic fish. The mean rates for the various groups are approximately as in Survey I, but with more Scombrids on the inner - and less Carangids on the outer shelf. The sardinella, thread - and scaled herrings were the most common Clupeids and bumper, bluntnose jack and bigeye scad dominated the Carangids. The spotted Spanish mackerel appeared to be more common than the king mackerel as in Suriname.

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

INNER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
339	20	6.80	150.80	2.40			235.20
340	27		0.30			0.70	55.90
341	28						133.80
342	23			1.20		30.00	118.40
343	19						439.20
344	24					9.60	462.40
345	25		2.60		0.20		153.40
349	49					70.20	22.00
350	45			0.20		133.80	76.20
351	27						184.50
352	22		0.80	0.60	0.20	0.40	60.50
354	24	12.00	118.90				132.90
355	22						77.40
356	17	23.80	356.80				511.20
357	22		16.00				375.00
358	15	12.93	206.08				150.69
360	23	25.37	77.84				284.82
361	42					1.20	36.60
362	56						11.00
363	44					0.20	221.00
364	39			76.80		905.60	255.20
365	37		3.80				73.10
366	35		10.00	21.20		35.60	207.00
369	15	56.20	106.00				288.20
370	29		8.00				768.20
371	18	142.40	146.00				288.20
372	57						64.60
375	11	6.00	157.40				309.20
376	52					3.80	80.40
377	30			0.30		0.80	34.40
378	14	1.80	5.60				282.80
379	43						57.90
MEAN		8.98	42.72	3.21	0.01	37.25	201.60

OUTER SHELF

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
346	72					33.80	13.20
347				0.10		2.80	4.90
348	77			9.10		8.40	97.64
367	68		1.60			72.80	38.80
368	66		3.60	0.80	7.20	22.40	62.20
373	81					2.40	24.80
374	84			0.80	63.40	40.80	14.40
380	61						57.00
381	76					79.60	16.10
382	76		0.30	3.00	1.20	84.00	62.70
383	82		3.20	4.80	5.60	127.20	93.20
384	68		13.80		2.40	3.00	80.20
MEAN			2.93	1.55	7.05	39.88	51.71

Annex IV shows pooled length distributions 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
339	20	2.40	16.00				376.80
340	27			0.30	18.00		38.60
341	28	50.00		30.40	26.00		27.40
342	23	30.40		31.60	36.80		50.80
343	19	9.60	102.00	46.80	13.20	18.00	249.60
344	24	8.80	5.60	27.20	312.80		117.60
345	25	24.00		72.60		0.60	59.00
349	49			2.20			90.00
350	45			7.60	13.20	0.40	189.00
351	27	36.00		128.00			20.50
352	22	3.60		30.80		1.20	26.90
353		540.00	85.60	69.80	22.60	2.80	1.80
354	24	62.00		11.40			190.40
355	22	42.60		19.80	1.20	1.20	12.60
356	17	58.80		5.60	2.80		824.60
357	22	247.00	36.00	24.00	15.00	4.00	65.00
358	15	0.46	18.47				350.77
360	23	72.51	30.77	33.94			250.81
361	42			18.80		3.80	15.20
362	56			1.00			10.00
363	44	43.80		168.20	0.40		8.80
364	39	7.20		145-60		14.40	1070.40
365	37	43.00	22.00	1.50		0.40	10.00
366	35	32.40	26.40	18.40	18.20	8.80	169.60
369	15	33.60	36.80	0.80	27.40		351.80
370	29	64.80	684.00	1.80	6.00	3.00	16.60
371	18	20.00	4.00	40.80	7.20		504.60
372	57			44.00	18.60		2.00
375	11	3.00	154.20	69.00			246.40
376	52			34.30	11.60		38.30
377	30		20.00	1.90	12.00		1.60
378	14	55.20	116.00.	4.80			114.20
379	43			15.70	2.40	26.80	13.00
MEAN		45.19	41.15	33.60	17.13	2.59	167.11

OUTER SHELF

ST. NO.	DEP.	Sardines	Anchovies	Carangids	Scombrids	Barracudas	Other
346	72			8.20			38.80
347	61			0.10			7.70
348	77	1.04		50.40			63.70
367	68			0.40			112.80
368	66						96.20
373	81			12.20			15.00
374	84			6.60			112.80
380	61	1.80		3.00		2.40	49.80
381	76	0.40		7.90		0.60	86.80
382	76			0.60	1.20		149.40
383	82						234.00
384	68			8.00	2.00	1.00	88.40
MEAN		0.27		8.22	0.48	0.33	93.82

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 600m. Record of the fishing stations are shown in Annex II from st. 376 onwards. For the purpose of analysis an overlap has been made with stations east of the Orinoco delta. Table 7 shows the standardized catch rates by the broad groups for all hauls including the deep water slope. Catch rates for demersal fish are lower than in Survey I, but this is at least partly an effect of the fishing on the slope and more hauls for shrimp at night. Sharks and squid appear to be more abundant than in February.

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
376	52	3.80	33.80			45.90	0.70
377	30	1.10				33.90	0.50
378	14	7.40	28.80	3.60		228.00	22.40
379	A3		11.40			45.30	1.20
380	61		1.40	1.00	4.80	7.60	42.20
381	76	79.60			2.80	8.90	4.40
382	76	88.50		4.80	0.60	1.80	55.50
383	82	140.80	5.60	5.60	3.20		78.80
384	68	19.20	2.00	9.00	5.60	11.00	52.60
385	67	18.80	1.00	10.20	2.40	3.80	38.00
386	17	764.20		10.00		195.20	6.20
387	43	33.00	20.00		3.00	89.00	72.80
388	22	2.20	6.40			171.00	40.80
389	8	156.00	6.00	106.50		4.30	56.60
390	401		0.71	4.59	7.06	1.41	48.53
391	511			1.90	0.50		16.60
392	399		0.20	6.30	2.00	0.20	17.85
393	271	0.26	9.00	0.26	16.94	0.79	28.15
394	202	20.60			2.20	5.00	20.10
395	507			7.50	0.30	2.80	34.40
396	403		5.70	7.80	8.10	0.30	57.90
397	606			9.80	20.40	1.50	66.00
398	382		0.50	1.20	1.90		40.60
399	77	103.00		6.20	1.00	1.50	313.50
400	58	61.50	3.30	17.50	7.20	3.00	97.20
401	56	13.20	1.60	8.20	0.40	4.80	13.60
402	13	46.80	29.60	15.00		217.80	52.00
403	52	35.60		3.20		5.20	17.20
404	37	321.00	37.20		12.40	1646.20	51.20
405	11	13.40	2.80			52.50	3.80
406	37	169.40	141.00			545.80	46.30
MEAN		67.72	11.23	7.75	3.32	107.56	45.08

Catch rates for deep water shrimp ranged up to abt. 10 kg/hour with a species of the Solenoceridae family dominating at abt. 400m and Plesiopenaeus edwardsianus at 600 m. Most of the shrimp were large sized.

At intermediate depths on the shelf shrimp catches at night ranged from 3 to 8 kg/hour and consisted of pink - and redspotted and a few brown shrimp.

Table 8 shows the catch rates for demersal fish in the shelf hauls. There were in contrast to Survey I few large catches of croakers, but the species composition was much the same as previously. Some snappers were found on the outer shelf, mainly Pristipomoides macropthalmus.

Table 9 shows the catch rates for pelagic fish by families for the shelf hauls. Scaled -and dogtooth herring and pellona dominated the Clupeids, and lookdowns the Carangids. Spanish mackerels were more abundant than in February with the spotted species most common.

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

ST. NO.	DEP.	Catfish	Croakers	Grunts	Groupers	Snappers	Other
376	52					3.80	80.40
377	30			0.30		0.80	34.40
378	14	1.80	5.60				282.80
379	43						57.90
380	61						57.00
381	76					79.60	16.10
382	76		0.30	3.00	1.20	84.00	62.70
383	82		3.20	4.80	5.60	127.20	93.20
384	68		13.80		2.40	3.00	80.20
385	67		12.60		4.80	1.40	55.40
386	17	94.00	670.20				211.40
387	43		33.00				184.80
388	22		2.20				218.20
389	8	73.20	82.80				173.40
399	77			3.50	7.00	92.50	322.20
400	58		45.60		4.80	11.10	128.20
401	56		10.80		2.00	0.40	28.60
402	13	14.00	32.80				314.40
403	52		35.20	0.40			25.60
404	37	14.60	295.40	11.00			1747.00
405	11	5.40	8.00				59.10
406	37	84.60	84.80				733.10
MEAN		13.07	61.13	1.05	1.26	18.35	232.67