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.

Guatemala.

The records of all the fishing stations made during this part of the cruise are shown in Annex 2, where those numbered from 418 through 448 refer to the area off Guatemala (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 refering to the depth of the transition layer, ie. above and below 100 metres. The inshore catches consist of a large variety of species, and 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 the bumpers (74%) and the anchovies (17%), whereas fish from a large variety of species constitute the community grouped as bottom fish. The dominating bottom fish are grunt (25%), snapper (11%) and croaker (Sciaenidae) (9%). Some few lobsters (Panulirus gracilis) were caught in the coastal area to the southeast. The mean catch rate from 20 hauls inshore, including all species, is 450 kg/h. Abt. 2% of the catch is shrimps. Most of the shrimp caught at st. 420 is of low commercial value.

Table 1. Fish catches, inshore community, Guatemala. Catch rates in Kg. per hour towed.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
420	94		562	70	632
421	58	7	44	2	53
422	24	16	18		34
423	37	50	316	24	390
424	74		389	30	419
425	30	176	333	6	515
426	31	45	109	3	157
432	57	78	689		767
433	20	117	35		152
434	38	24	227	14	265
435	27	135	166	9	310
436	67	650	1261	14	1925
440	85	360	87		447
441	44	500	298		798
442	22	131	58	2	191
443	45	176	272		448
444	21	21	10		31
445	33	101	123	4	228
447	52	883	293		1176
448	21	52	12		64

Fishing offshore was arranged to cover different depths between 100 and 300 m in testing for langostino and shrimp. The mean catch rate from 9 offshore stations is 0.8 tons/hour and the main groups of species are shown in Table 2. The dominating fish species are sea bass, Family Serranidae (34%), and fish of the Family Scorpaenidae (17%). One large catch of silver smelt Family Argentinidae was made (st.439). Good catches of langostino (Pleuroncodes planipes) were made at the edge of the shelf below 200 m depth but the catch rate is low compared to that found in the El Salvador/Nicaragua region. The deep sea shrimp (Heterocarpus vicarius) which were found to be abundant more south was absent and mantis shrimp (Squilla sp) was found in large quantities at depth below 200 m. On the whole these results indicate that the offshore part of the shelf of the Guatemala region has a somewhat poorer fauna compared to that observed in the south.

Table 2. Fish catches, offshore community, Guatemala. Standardized to rates of kilo per hour towed.

St. no.	Depth m	Fishes	Squilla	Langostino	Total
418	156	257	361	71	689
419	252	142	1467	391	2000
427	118	306			306
428	165	156	308		464
429	247	58	324	669	1051
430	173	317	281		598
431	118	493	19		512
438	200	142	5	373	520
439	232	535	40	475	1050

Golfo de Tehuantepec, Mexico

The fishing stations worked in Mexican waters are listed in Annex 2, stations no 449 through 486. Results from the hauls in the areas of inshore fish distribution, made at prelocated positions and worked during day-time, are shown in table 3. The stations are ranged from the border of Guatemala and westwards to the area off Salina Cruz. During the previous survey it was found that the catches made south of Barra de Tonala differ in composition and size compared to those being made in inshore waters to the north of that position. The stations in Table 3 are listed accordingly, those being worked south of Barra de Tonala are shown above the open line of the table. The mean catch in the north standardized to rates per hour towed and grouped as pelagics, bottom fish and shrimps is 515 kg/h, consisting of 58 % pelagics, 41 % bottom fish and 1 % shrimps. The figures for the area south of Barra of Tonala are 378 kg/hr, corresponding to the above mentioned groups 45%, 54% and 1% respectively. The main reason for this difference in catch rate and species composition is the large catch of pelagics (3047 kg/hr) at st. 485, which consisted of some 80 % bumper (Chloroscombrus orqueta). Otherwise there are small differences in catch rates by species at the two areas. The pelagics are dominated by bumpers, whereas grunts (41%), gerrids (18 %) and catfishes (7%) predominate in the group of bottom fish.

Table 3. Fish catches, inshore community, Mexico. Catch rates in Kg. per hour towed.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
449	38	57	282		339
450	22	105	147	1	253
451	45	84	153		237
455	84	928			982
461	54	465	480		945
462	25	52	134	15	201
463	44	180	423		603
464	28	30	105	1	136
465	25	119	218	7	349
466	46	33	235	12	280
469	58	32	432	1	465
470	37	33	103	3	139
471	24	138	142	5	285
472	40	165	88		253
473	24	125	144		269
456	54	1010	405		1415
457	56	340	648		988
458	58	59	183		242
459	58	50	121		171
460	52	23	126		149
474	26	66	178	5	249
475	41	50	74		124
482	36	49	158	4	211
483	28	143	24		167
484	37	46	8		54
485	23	3660	328		3988
486	24	94	388		482

Table 4 shows the records of the offshore trawling for langostino, squilla and shrimps. These are prelocated catches, all but station no 476 being made during night. The latter gave a record catch of fish of 4 tons/hour, and consisted mainly of jack mackerel (Decapterus sp). The catch rate of fish in the former stations are relatively low and consist mainly of fish from the family Scorpaenidae (66%). Good catches of langostino (Pleuroncodes planipes) and Squilla sp were made at the edge of the shelf below 150 m depth, but the samples are too few to assess the abundance or destribution of these stocks in the Mexican region. No deep sea shrimp was caught. region. No deep sea shrimp was caught.

Table 4. Fish catches, off shore community, Mexico. Standardized to rates of kilo per hour towed.

St. no.	Depth m	Fishes	Squilla	Langostino	Total
453	226	44	630	540	1214
454	153	103	360	1224	1687
467	174		52	988	1040
468	143	7	3	5	15
476	103	4000			4000

Some trials were made for fishing Crystal shrimp (Penaeus brevirostris) in the 50 - 100 m depth range in the north western part of the Gulf. During the previous cruise this species gave insignificant catches in daylight fishing compared to night fishing, and the stations were therefore sampled during night. The results, standardized to catch/hour towed (kilos), are shown in Table 5. Good catches of crystal shrimp Penaeus brevirostris were made between 80 and 100 m depth, which is some 20 m deeper then the main distribution depth found in March. The other shrimp species, except for a few specimens of brown shrimp, are of low commercial value. The catch rate of fish is low, the main species are lizard fish Family Synodonteidae and catfish (Family Ariidae).

Table 5. Catches of crystal shrimp, Golfî de Tehuantepec, Mexico. Catch rate in kilo per hour towed.

St. no.	Depth m	Fish	Crystal shrimp	Other shrimps	Total
477	56	242		3	245
478	79	95	6	5	106
479	89	116	40	11	167
480	99	144	41	5	190
481	83	62	75		137