5. Results of fishing experiments

Guatemala
Golfo de Tehuantepec, Mexico

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.

Guatemala

The records of all the fishing stations made during this part of the cruise are shown in Annex 2. The catch composition and catch rates can conveniently be described by reference to an inshore and an offshore community. The fish catches made, standardized to rates per hour towed (in kilos), and grouped as pelagics (clupeids, anchovies, carangids), bottom fish, shrimp and shelf squid are shown in Table 1. Most catch rates are a few hundred kilos or less but four catches ranged between and two tons/hr and they had large components of pelagic fish, mostly bumper and lookdown, but also barracudas and sardines appeared in the bottom trawl catches. Among the demersal species butterfish appeared in nearly all the catches with a mean rate of 33 kg/hr. Snappers were found in 7 catches with a mean rate of 24 kg/hr and sharks in 14 of the 23 hauls with a mean rate of 22 kg/hr. Less than 1% of the catches consisted of shrimp and catch rates were clearly lower than in June. Small sized shelf squid (Lolliguncula and Loliolopsis) appeared in a few of the hauls at a depth of 80 - 90 m as off Nicaragua.

Table 1. Fish catches, inshore community, Guatemala. Catch rates in kg. per hour towed, bottom trawl.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimp	Squid	Total
750	25	39	31	1		71
751	80	6	26		18	50
752	40	27	68			95
753	35	339	697	1	1	1038
754	87		189		46	235
755	37	103	122	1	7	233
756	47	58	121	1		180
758	70		69	1		70
761	90		113		1	114
762	43	55	254			309
763	18	124	46			170
764	43	32	128			160
765	85		68	1	1	70
766	13	573	743			1316
767	35	1530	603			2133
769	66		124	15		139
770	27	89	166	9		264
771	19	57	254	4		315
772	34	839	642	6		1487
773	15	131	53	10	1	195
779	39	11	89			100
780	13	58	103	3	2	166
782	100		17			17

Table 2 shows the record of the catch rates in six hauls from trawlable bottom offshore, between 150 and 250 m depth. The availability of langostino in good quantities in the northwestern part of the slope is confirmed. Deep sea shrimp (Heterocarpus) occurred only sporadically, but the mantis shrimp (Squilla) is abundant in deeper waters.

Table 2. Fish catches, offshore community, Guatemala. Standardized to rates of catch per hour’s tow, kilos.

St. no.	Depth m	Fish	Squilla	Langostino	Total
759	175	36	280	464	780
760	245	59	392	466	917
774	180	130	58	307	495
775	165	260	114	464	838
783	152	379	108	3513	4000
784	227	246	1591	1763	3600

Some stations were worked off the shelf with light and jigging testing for giant squid, but with negative results.

Golfo de Tehuantepec, Mexico

The fishing stations worked in Mexican waters are listed in Annex 3, and the results from the hauls in the areas of inshore fish distribution are shown in Table 3. The catch rates were lower than during the two previous surveys. Only a few hauls in shallow waters gave high rates and these catches were dominated by pelagic fish, mainly bumper. The low catch rates especially in somewhat deeper water is likely to be a seasonal phenomenon perhaps associated with the observed change in the oceanographic environment which may have affected the depth distribution of the fish and the productivity of the waters. Anchovies and sardines appeared in both pelagic - and bottom trawl, but generally with low catch rates, a mean of abt. 50 kg/hr. Barracudas showed better rates, ranging up to abt. 500 kg/hr. Of the demersal group butterfish, abundant in the March survey were now only found in 11 hauls with a mean rate of 36 kg/hr. The catch rates for crystal shrimp were also lower than in the previous surveys and shelf squid only appeared sporadically.

Table 3. Fish catches, inshore community. Gulf of Tehuantepec, Mexico. Catch rates in kg. per hour towed, bottom trawl.

St. no.	Depth m	Pelagic fish	Bottom fish	Shrimps	Total
781	22	314	393	5	712
788	23	92	206	3	301
789	43	19	698		717
792	52	8	56		64
793	14	103	71	4	178
794	22	195	215	2	412
796	15	67	349	18	434
797	50	2	151	1	154
800	43	53	110		163
801	16	21	67		88
802	50		18		18
803	22	242	153	3	398
805	18	41	19	3	63
806	43	6	227	10	243
807	62		28	3	31
808	31	1958	307	7	2272
809	17	20	164		184
810	60		138	23	161
811	55		163	7	170
813	42	65	245		310
815	27	22	20		42
816	31	121	132		253
817	58		85	1	86
818	65		56	22	78
819	63		59	7	66
821	46		52	1	53
822	16	1768	628	4	2400
823	32	14	51		65
824	18	114	365	8	487
825	57		8		8

Table 4 shows the records of the offshore trawling for langostino, squilla and fish. These results confirm the findings from the previous surveys that there exists a high availability of langostino over the depth range 150 - 200 m in the southeastern part of the Gulf.

Table 4. Fish catches, offshore community, Mexico. Standardized to rates of catch per hour’s tow, kilos.

St. no.	Depth m	Fish	Squilla	Langostino	Total
785	202	190	237	3073	3500
786	162	325	211	5190	5726
790	182	64	85	1851	2000
798	164	22	544	1434	2000
799	196	15	253	336	604
814	148	26	91		117