5. Results of fishing experiments

Some of the results of the fishing experiments are commented on below. One should note, however, that in a programme for "swept area" biomass estimation, the trawl stations are positioned 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 and abundance of bottom fish on the shelf.

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.

Nicaragua.

The records of all the fishing stations made are shown in Annex 2. All bottom trawl stations in the inshore area at depths less than abt 60 m represent prelocated hauls for faunistic studies and swept area estimates.

The 22 hauls made inshore gave catch rates pr hour distributed as follows:

Catch group (tons/hour):	0-.03	.03-.1	.1-.3	.3-1	1-3	>3
No of catches			7	14	1

The mean of these was 514 kg/hr. This is about the same level as during survey II, 430 kg/hr, but considerably higher than the mean rate of 306 kg/hr found during Survey I. The catch rates thus in a general way confirm the impression of changes of fish availability demonstrated by the the acoustic survey findings.

The catches of these inshore stations standardized to rates per hour towed (in kilos) and grouped as pelagic fish, bottom fish and shrimps plus lobsters are shown in Table 1. The dominating pelagic species are anchovies, thread herring, carangids, mackerel and barracudas. The barracudas were quite common occurring in 16 of the catches with a mean rate of abt 70 kg/hr, Spanish mackerel in 15, but with a mean of only 17 kg/hr. Of commercial species of demersal fish snappers were found in 13 hauls with a mean rate of abt 80 kg/hr and the highest catch ranging up to 425 kg/hr., sharks in 17 hauls with a mean of 19 kg/hr and commercial croakers occurred in 15 of the inshore hauls with a mean rate of 25 kg/hr.

Table 1. Fish catches, inshore community, Nicaragua. Catch rates in kg. per hour towed.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps Lobster	Total
675	45	30	717	4	750
676	70	5	231		236
677	40	301	256	6	563
678	40	185	373	4	562
679	26	326	363	2	691
680	24	173	234	10	417
681	52	28	786	3	817
682	55		350	5	355
683	54	1	99	18	118
684	67	2	137	43	182
685	20	169	42	2	213
686	38	58	483	2	233
687	20	131	285	1	417
688	30	253	346	4	593
689	34	443	295		738
690	17	59	194	1	254
691	20	572	211		783
692	26	221	303	7	531
694	50	4	135	6	145
706	18	161	317	3	481
707	30	788	762	6	1556
708	20	179	433	6	618

Fishing offshore was primarily arranged to cover different depths between 120 and 300 m in testing for langostino and shrimp, but some hauls were also made on the shelf between 60 and 120 metres. Roughly half of the hauls in the offshore region gave significant catches of fish, langostino or shrimp and these are shown in Table 2 as rates per hour. It is seen that 14 hauls of langostino range from 0.5 to 18 tons/hr, the highest rates deriving from hauls at 110 - 140 m of depth. The biggest sizes of langostino were, however, obtained in hauls at intermediate depths, both the deep and shallow hauls tended to have a mixture of sizes. The deep sea shrimp, "cabezon" only appear in hauls from 250 m and beyond. These catch rates of shrimp are well below the highest rates from Survey II, but are still significant. The catch rates in 8 hauls with "deep sea fish" ranged from abt 1 to 20 tons/hr and consisted of small sea basses, gurnards and silver smelts. Cutlassfish which was common in the two previous surveys now appeared only as juveniles. - In nine hauls at intermediate depths at night with the objective of testing for crystal shrimp (P. brevirostris) only three had catch rates exceeding 1.0 kg/hr, and the highest was 30 kg/hr. Some hauls were made testing for dart squid (Loliolopsis) in locations where the species had been caught previously. Stations 704 and 705 at abt. 100m depth gave rates of 400 kg/hr of small sized probably juvenile squid in very nearly clean catches.

Table 2. Bottom trawl stations with relatively large catches, offshore community, Nicaragua region. Standardized to rates of catch per hour's tow, tons.

Station no	Depth m	Fishes	Langostino	Shrimps	Total
636	160	20.0			20.0
637	270			0.244	0.3
639	290			0.464	0.9
640	150	3.6			3.6
645	250			0.319	0.6
648	240		0.9		0.9
649	180		1.6		1.8
650	290		1.1	0.368	1.5
651	115	2.2	11.4		14.0
655	185		2.4		2.7
656	240		2.3		2.4
658	110		11.2		12.0
659	140		18.1		20.0
662	280			0.570	0.8
665	170	1.1			1.5
668	200	3.0			3.3
670	200	0.9	3.0		4.0
671	170	2.5			3.0
696	120		0.8		1.0
698	180	3.2	0.5		4.0
699	180		2.2		2.3
700	250		2.9	0.092	3.3
703	240		1.7	0.072	2.9

A limited effort was spent on testing the availability of oceanic squid with light and jigging, see Table 3. A change was made in the use of the gear from 7/9 onwards: up till then 2-3 jiggs had been fished in the surface water down to 10 - 15 m of depth. Now one jig was fitted for fishing down to 100m. On the two last stations this resulted in hooking of large squid a good number of which were lost when being brought up of the water.

Table 3. Testing for oceanic squid (Dosidiscus gigas) with light and jigging, Nicaragua .

Date	Hour	Latit.	Longi.	Depth	Observations	Catch
		° '	° '			N	W (kgs)
28/8	23	11 07	86 49	330m	Medium	18
28/8	23	11 33	87 14	300m	Medium	7	4
30/8	00	11 30	87 19	>500m	Medium	10	4.5
30/8	02	11 26	87 05	170	Negative	0
30/8	20	11 45	87 29	300m	Negative	0
30/8	21	11 38	87 31	>500m	Small	0
30/8	23	11 41	87 24	400m	Some	12	5.2
31/8	21	10 58	86 41	300m	Some	1	1
5/9	04	11 53	87 37	>500m	Some	6	3.5
5/9	20	12 06	87 54	300m	Very small	0
5/9	21	12 03	87 58	>500m	Lost 3 big	0
6/9	24	12 24	88 15	>500m	Medium	7	2.5
7/9	02	12 15	88 21	>500m	Lost many big	6	16.5
7/9	03	12 20	88 20	>500m	Lost many big	8	17.2

Golfo De Fonseca.

In the Golfo De Fonseca 7 prelocated trawl stations were made, see Annex 3, and the catch rates in kg/h by stations and groups are shown in Table 4. The mean catch rate including all species is 338 kg/h. Abt. 5% of the catch is shrimps. The pelagics are dominated by clupeids (60%), the bottom fish by croaker (family Sciaenidae), butter fish and catfish (family Ariidae).

Table 4. Fish catches in Golfo De Fonseca. Catch rates in kilos per hour towed.

St. no	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
709	11	46	177	22	245
710	15	44	269	29	342
711	16	136	82	20	361
712	26	236	294	0	530
713	16	102	192	26	320
714	22	29	19	8	56
715	45	113	388	10	511

El Salvador

The distribution of the fishing stations inshore is shown in Figure 1 and Annex 4 gives the catch records for each haul. The 16 hauls made gave catch rates pr hour distributed as follows:

Catch group (tons/hour):	0-.03	.03-.1	.1-.3	.3-1	1-3	>3
No of catches	1	2	6	5	1

The mean of these was 310 kg/hr which is somewhat lower than the 440 kg/hr obtained in Survey II. One should note that most of the fish observed acoustically here are pelagic schooling fish which are not very vulnerable to bottom trawl.

The catches of these inshore stations standardized to rates per hour towed (in kilos) and grouped as pelagic fish, bottom fish and shrimps are shown in Table 5. The dominating pelagic species are barracudas, anchovies, thread herring and carangids. Barracudas occurred in all catches with rates ranging up to 500 kg/hr and a mean of 70 kg/hr. Various scads were also common, but with a mean rate of only 23 kg/hr. Among the demersal species butterfish, Peprilus were common with a mean rate of abt. 35 kg/hr. Snappers were found in 10 catches with a mean rate of 10 kg/hr and sharks in 11 with a mean of 13 kg/hr.

Table 5. Fish catches, inshore community, El Salvador. Catch rates in kg per hour towed.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
716	52		1		1
717	23	204	143	3	350
718	23	70	68	1	139
719	31	236	410	3	649
720	18	48	60	1	109
735	32	114	134	17	265
736	17	52	30		82
737	25	266	262	5	533
738	22	164	76	3	243
739	33	265	215	3	483
740	28	148	152	5	305
741	44	45	73		118
746	47	668	639	2	1309
747	22	23	75	1	99
748	34	126	140	12	278
749	51	5	156	4	165

A few tests were made of the availability of dart squid, Loliolopsis in locations where they had been caught previously, but only small catches of juveniles were obtained.

Fishing offshore was primarily arranged to cover different depths between 120 and 300 m in testing for langostino and shrimp, but some hauls were also made on the shelf between 60 and 120 metres. About 2/3 of the hauls in the offshore region gave significant catches of fish and langostino and these are shown in Table 6 as rates per hour. Deep sea shrimp were as previously only found in small quantities, but mantis shrimp is very common and abundant in this area especially in deep water. Whether this species may have any future commercial value is uncertain. As can be seen from the table catch rates are generally high for both langostino and mantis shrimp. The few high catches of fish obtained in offshore waters consisted mainly of silver smelt.

Table 6. Bottom trawl stations with relatively large catches, offshore community, El Salvador shelf. Standardized to rates of catch per hour's tow, tons.

Station no	Depth m	Fishes	Langostino	Squilla	Total
723	244		0.4		0.5
724	175	1.7	1.9		3.6
726	157		0.3		0.5
727	200	4.8			5.0
729	252		1.5	0.8	2.5
730	230		1.4	0.4	2.1
732	197		0.7		0.8
733	246		1.0	3.5	4.5
734	180		1.0	0.4	1.5
742	250		1.3	1.6	3.0
743	250		0.8	0.2	1.0
744	190		3.2	0.3	4.0

A limited effort was spend in testing the availability of oceanic squids by light and jigging. Eight stations were worked off the shelf mostly beyond 500m of depth. A small catch was obtained in one of the tests. Very small sized squid were observed on most stations perhaps indicating that this is the season of recruitment as seems to be the case also for the dart squid on the shelf.