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.

Guatemala.

The records of all the fishing stations made during this part of the cruise are shown in Annex 2. The distribution of catches by size categories are as follows:

Catch group(tons/hour)	0 - .03	.03 - .1	.1 - .3	.3 - 1	1 - 3	>3
	3	3	5	9	2

Mean catch and number of hauls by bottom depth zones are:

Bottom depth stata:	0 - 29m	30 - 59m	60 - 99m	100 - 149m	150 - 199m	>200m
Mean catch(Kg/hour)	485	590	28	295
Number of hauls	15	4	2	1	0	0

The successful bottom trawl hauls made in the shallow waters (0-60m) are summarized in Table 1, standardized to rates per hour towed, and grouped as Pelagic 1 (clupeids, anchovies), Pelagic 2 (carangids, barracudas), “Valuable” (Snappers, croakers), Sharks (and rays) and Crustaceans (shrimps and lobster). The remains of the catch, which is mainly small sized bottom fish, go in the category “Other”. The mean catch from 19 hauls is 510 Kg/hour of which 60 % is small pelagic fish, 31 % small demersal fish, 4% snappers and croakers and 3% shrimps. Sharks and rays make up only 1% of the total.

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

STA. NO.	Pelagic 1	Pelagic 2	“Valuable”	Sharks	Shrimp&Lob	Other
1033	13.40	295.40	10.60		51.80	52.20
1034	88.20	204.20	10.70		2.00	84.60
1035					0.90	21.00
1036	0.30	37.60	4.00	1.60		13.90
1037			9.40			8.50
1039	69.00	582.60			2.20	164.60
1043	30.20	14.40	25.20		14.00	147.40
1044	112.00	126.00	33.80		10.00	330.00
1046		10.10	0.30			36.70
1047	305.20	185.60	7.20			296.80
1048	166.00	64.60	5.00			65.20
1049	9.20	82.60		34.60	2.40	57.80
1050	150.60	711.00	28.60	3.00	4.80	778.00
1051	44.12	36.80	2.40	36.00	3.40	28.00
1052	225.60	942.40	105.60		133.30	707.20
1053	8.20	25.80	53.60	10.00	26.40	38.20
1055	435.00	192.80	7.20	20.00	2.20	39.20
1056	19.80	283.20	38.80	13.20	12.20	274.40
1057	158.70	137.40	10.10		0.30	48.00
MEAN	96.61	206.97	18.55	6.23	13.99	167.98

Total number of stations: 19

Preliminary estimates of densities have been made by species and depth zones. These calculations, which are based on the swept area method, assumes that all fish within the path of the trawl are caught, and does not include the small pelagic fish. The results from this analysis are included as Appendix 6. It estimates mean density in the shallow areas to about 10 tonnes/nm². The shrimp is estimated to about 400 kg/nm² in the 10-30m bottom depth zone, and 300 kg/nm² in the 30-60m zone. The estimates for shrimp could be underestimates, as the fishing gear might not be optimally rigged for such fishery. More thorough analysis will be made for the final report.

Golfo de Tehuantepec, Mexico

The records of all the bottom trawl stations made during this part of the cruise are shown in Annex 2. The distribution of catches by size categories are as follows:

Catch group(tons/hour)	0 - .03	.03 - .1	.1 - .3	.3 - 1	1 - 3	>3
	9	12	17	5	3	1

Most of the catches fall in the range 30 to 300 kg/hour. One catch exceeding 3 tonnes/hour was 16 t/hour and consisted purely of catfish (Bagre panamensis). The mean catch from 47 hauls is 550 Kg/hour, including the catfish haul, and drops to 210 Kg/hour if this catch is excluded.

Mean catch and number of hauls by bottom depth zones are:

Bottom depth stata:	0 - 29m	30 - 59m	60 - 99m	100 - 149m	150 - 199m	>200m
Mean catch(Kg/hour)	368	936	76	41
Number of hauls	18	20	6	3

The successful bottom trawl hauls made in the shallow waters (0-80m) are summarized in Table 1, standardized to rates per hour towed, and grouped as Pelagic 1 (clupeids, anchovies), Pelagic 2 (carangids, barracudas), “Valuable” (Snappers, croakers), Sharks (and rays) and Crustaceans (shrimps and lobster). The remains of the catch, which is mainly small sized bottom fish, go in the category “Other”. The mean catch from 42 hauls is 605 kg/hour including the above mentioned catfish haul (st. no. 1086), and 230 kg/hour excluding it. Of the total catch, excluding st. no. 1086, 36% is small pelagic fish, 55% small demersal fish, 3% snappers and croakers and 4% shrimps. Sharks and rays make up only 2% of the total.

Preliminary estimates of densities have been made by species and depth zones. These calculations, which are based on the swept area method, assumes that all fish within the path of the trawl are caught, and does not include the small pelagic fish. The results from this analysis are included as Appendix 7. It estimates mean density in the 10-30m bottom depth zone to abt. 10 tonnes/nm² and 30-50m to 9 tonnes/nm². Both zones are dominated by grunts (Orthopristis chalceus) which make up 32 and 48 % of the estimated biomass respectively. The mean of the 50-70m bottom depth zone is dominated by the single high catch of catfish and is not reliable. The densities of shrimp by depth zones are estimated as follows;

Bottom depth strata	10 - 30m	30 - 50m	50 - 70m	70 - 150
Density kg/nm2	120	880	1300	70

The estimates for shrimp could be underestimates, as the fishing gear might not be optimally rigged for such fishery, and the hauls beyond 50 m are to few to give statistically valid results. More thorough analysis will be made for the final report, when the data from the various coverages will be merged.

Table 2. Fish catches, inshore community, Gulf of Tehuantepec. Catch rates in kg. per hour towed, bottom trawl.

STA. NO.	Pelagic 1	Pelagic 2	“Valuable”	Sharks	Shrimp&Lob	Other
1058	7.20	190.80				6.12
1059		9.02		10.00		52.00
1060	40.76	65.80	14.80		5.60	60.80
1061		21.00		0.60		82.00
1062		1.10		1.40	1.40	25.00
1063	34.40	46.80	25.60		18.00	275.00
1064	30.40	8.70	35.46		29.20	73.20
1065		4.80			0.20	125.80
1066	1.60	328.00			8.80	130.40
1067		1.52				28.12
1068	1231.40	253.80				110.40
1069		11.84		1.20		14.40
1070		46.50			0.60	241.00
1071	6.96	42.00	4.60		1.20	20.20
1072		58.76			0.40	50.64
1073	16.20	13.20	7.40		2.40	137.60
1075		0.10				5.90
1076		17.30	0.60			16.00
1077	67.60	61.80	98.20	4.80		186.40
1078	24.00	47.40	49.80			228.60
1079	1.40	34.00		10.00		2.20
1080		53.00	1.00			90.86
1081
1082		9.60		3.30	0.40	31.70
1083		110.00	34.00	20.00	5.20	984.80
1084		37.80		13.80	0.80	128.00
1086		46.80			46.80	15906.60
1087		0.20				29.00
1092				8.00	125.20	905.20
1093					4.20	33.60
1094		0.20			5.18	71.60
1095					39.64	41.48
1096					0.70	7.94
1097		5.00	4.60	1.40		62.20
1098		112.40				106.00
1099		17.00	31.00			117.54
1100		0.60		2.60		58.10
1101	0.40	32.40				93.40
1102		220.60	19.60	84.80	4.20	482.40
1103				6.20	34.00	72.62
1104					30.00	71.00
1105				6.00	60.40	51.60
MEAN	34.82	45.47	7.78	4.15	10.11	505.18

Total number of stations: 42