5. Results of fishing experiments

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 during this part of the cruise are shown in Annex 2, those numbered from 338 through 383 refer to the area off Nicaragua, including Golfo de Fonseca (cfr. Figure 1). Most of the trawl stations represent prelocated hauls for faunistic studies and swept area estimates. The catch composition and catch rates can conveniently be described in an inshore and an offshore community referring to depths above and below abt 75 metres. The inshore catch rates are relatively low, but the catches consist of a large variety of species. The fish catches made, standardized to rates per hour towed (in kilos) and grouped as pelagics (clupeids, anchovies, bumpers), bottom fish and shrimps plus lobsters are shown in Table 1. The dominating pelagic species are anchovies and fish from the family Gerreidae dominate the bottom fish. The lobsters (Panulirus gracilis) was caught in the area southeast of P. Corinto only. The mean catch rate inshore (15 st.) including all species is 505 kg/h. Less then 3% of the catch is shrimps.

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
340	49	1045	409		1454
341	31	118	467	13	598
342	18	55	501	14	570
353	70	42	605	2	648
354	21	63	103	7	173
355	35	53	236	18	307
356	75	186	244	17	447
357	75	26	217	21	264
358	34	34	122	16	172
361	53	73	372	12	457
362	23	60	257	7	323
363	28	32	483	8	523
364	29	231	575	19	825
365	54	129	278		407
370	59	144	245	16	405

Fishing offshore was primarily arranged to cover different depths between 150 and 350 m in testing for langostino and shrimp, but a number of hauls were also made on the shelf itself between 75 and 150 metres. The mean catch rate offshore (21 st.) is 3.4 tons/hour and the main groups of species are shown in Table 2. The dominating fish species are silver smelt (Family Argentinidae), cutlass fish (Family Trichiuridae) and butter fish (Family Stromateidae). Good catches of langostino (Pleuroncodes planipes) and deep sea shrimp (Heterocarpus vicarius) were also made over a substantial area. These results show that there must be a considerable biomass of these stocks along the edge of the slope, between 100 and 400 metres depth.

Table 2. Fish catches, offshore community, Nicaragua region. Standardized to rates of catch per hour's tow, tons.

Station no.	Depth m	Fishes	Langostino	Shrimps	Total
338	159	1.5			1.5
339	90	0.7			0.7
343	149	6.0			6.0
344	271	0.9	4.8	6.3	12.0
345	372	0.8			0.8
346	397				0.0
347	305			0.1	0.1
348	187	0.6			0.6
349	357	0.1			0.1
350	282	0.2	7.1		7.3
352	120	9.0	4.8	0.2	14.0
360	147	1.2	0.6		1.8
366	79	0.3			0.3
367	246	0.1	1.1	0.3	1.5
368	147	1.6	1.4		1.9
378	98	2.4	1.2		3.6
379	101	2.5			2.5
380	107	2.3	5.0	0.7	8.0
381	177	1.7	2.9		4.6
382	252	0.1	5.4	2.2	7.7
383	353				0.0

Golfo De Fonseca.

In the Golfo De Fonseca 5 prelocated trawl stations were made and catch rates in kg/h by stations and groups are shown in Table 3. The mean catch rate including all species is 236 kg/h. Abt. 9% 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 3. Fish catches in Golfo De Fonseca. Catch rates in kilos per hour towed.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
372	26	46	155	21	222
373	14	11	72	40	123
374	16	74	82		156
375	30	12	448		460
377	51	12	168	43	223

El Salvador.

The fishing stations worked on the shelf off El Salvador are recorded in Annex 3, stations 384 through 417. Catch rates of arbitrarily located hauls inshore (less then 75 m depth) range from abt 70 to abt. 1900 kgs per hour's tow, with mean catch of 440 kgs./h. The anchovies dominate the pelagics (62%), whereas the barracuda (Family Sphyraenidae) and the butterfish are most numerous among the stocks grouped as bottom fish. Commercial bottom fish such as snappers (Family Lutjanidae) were scarce. Sharks occurred in numbers in some of the hauls.

Table 4. Fish catches, inshore community, El Salvador. Catch rates in Kg per hour towed.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
376	20	62	116	42	220
387	60	202	150	2	354
388	32	88	125	18	231
389	49	73	177	15	265
390	71	31	300	22	353
394	65	18	51	0	69
395	26	176	295	27	498
397	35	36	92	32	160
401	62	314	181	1	496
403	30	127	165	16	308
404	38	39	171	15	225
409	70	845	68	3	916
410	31	76	151	9	236
411	60	48	786	0	834
415	62	148	178		326
416	25	734	1019	163	1961

The mean catch rate offshore (17st.) is 2.2 tons/hour and the catch rate by main groups of species are shown in Table 5. The dominant fish species are silver smelt (st. 392), threadfin bass and butterfish. Good catches of langostino were made over a substantial area located at the edge of the shelf between 200 and 400 m depth. At st. 391, also a good catch of deep sea shrimp was made.

Table 5. Catch rates by fish group, langostino and shrimps offshore El Salvador. Catch rates in tons per hour towed.

Station no.	Depth m	Fishes	Langostino	Shrimps	Total
384	295	0.1	0.2		0.3
385	190	1.1	0.2	0.1	1.4
386	95	0.4			0.4
391	248	0.6	14.8	0.6	16.0
392	291	2.3	0.1		2.4
393	94	0.2			0.2
398	144	0.3	0.1		0.4
399	254	0.1	7.9	0.1	8.1
400	97	0.4			0.4
405	367				0.0
406	267	0.3	0.3		0.6
407	160	0.1	0.4		1.1
408	104	0.2			0.2
412	251	0.1	1.3		1.4
413	205	0.1	2.0		2.3
414	122	0.2	0.1		0.3