CHAPTER 3. THE COMPOSITION, DISTRIBUTION AND ABUNDANCE OF THE FISH RESOURCES

3.1 COLOMBIA
3.2 THE GULF OF PANAMA
3.3 PANAMA WEST COAST, THE GULFS OF COIBA AND CHIRIQUI
3.4 PANAMA, OVERVIEW OF SURVEY RESULTS AND ESTIMATES OF STANDING BIOMASS OF THE RESOURCES
3.5 COSTA RICA
3.6 NICARAGUA
3.7 GULF OF FONSECA
3.8 EL SALVADOR
3.9 GUATEMALA
3.10 THE GULF OF TEHUANTEPEC, MEXICO

3.1 COLOMBIA

3.1.1 Small pelagic fish
3.1.2 Demersal resources
3.1.3 Overview of survey results and estimates of standing biomass of the resources
3.1.4 Comments to the findings

Reference is made to the general descriptions of the shelf and the hydrographic regime under 2.1 and 2.2 above. The Colombian shelf is narrow, on average abt. 20 nm. There is little variation through the year in the vertical structure of the water masses with a well defined thermocline between abt. 50 and 100 m of depth. There is some variation in surface salinity resulting from river runoffs in the rainy season. The northernmost part of the Colombian shelf and slope may be influenced by the seasonal upwelling system of the Gulf of Panama.

3.1.1 Small pelagic fish

Distribution

Figure 3.1.1 shows the distribution of the pelagic fish as observed with the acoustic integration system for each of the surveys in April, August and October-November. Fish was only recorded inside the shelf edge and aggregations of some densities were mostly located well inshore and in the surface layer. The part of the shelf with densest aggregations are throughout the three surveys the shelf between Pta. Guascama and Buenaventura and the inshore surface assemblage here is dominated by the Pacific anchoveta, Cetengraulis mysticetus and thread herring Opisthonema libertate found in school areas and with Pacific bumper Chloroscombrus orqueta mostly inshore. Other accompanying carangids were lookdowns, mostly Selene peruvianus and bigeye scad, Selar crumenophthalmus with some green jack Caranx caballus and bright leatherjack, Oligoplites refulgens. Among the larger predators in this system were the sierra Scomberomorus sierra, barracuda Sphyraena ensis and sharks, mostly hammerheads Sphyrna spp.

Along the narrow shelf north of Buenaventura the formations offish recorded in the three surveys were more limited both in density and extension. The species composition of the assemblage above the thermocline was much the same as further south, but with less engraulids and clupeids and a higher proportion of carangids, especially bumper. A different fauna of pelagic fish was found below the thermocline from about the Gulf of Cupica northwards with hairtail Trichiurus nitens, scad Decapterus macrosoma and argentine Argentina aliceae. These species may also be present in deeper waters further south but the very steep slope here prevented observations and sampling. The most interesting of these species is the scad which was found in some abundance in the deeper offshore parts of the shelf off Panama.

Figure 3.1.1 Colombia. Fish distribution as recorded by the acoustic system, by surveys. (Survey 2)

Figure 3.1.1 Colombia. Fish distribution as recorded by the acoustic system, by surveys. (Survey 3)

Figure 3.1.1 Colombia. Fish distribution as recorded by the acoustic system, by surveys. (Survey 4)

Catch compositions

Complete catch records and various types of processed outputs giving catches by groups, species and surveys are available in the Data File to this report. Here we will only show some brief extracts of the catch data. The interpretation of these data should be subject to the reservations outlined in Chapter 1.3 above.

Table 3.1.1 shows the mean catch rates in kg/hour for the main groups of pelagic fish by survey, the three highest catch rates and the rate of occurrence expressed as the number of hauls where the group occurred over the total number of trawl hauls in the survey.

Table 3.1.1 Colombia. Catch rates in kg/hour by main groups of fish by surveys. Mean rate, three highest rates and rate of occurrence.
Survey			Mean rate	Highest rates	Rate of occurrence
	ENGRAULIDS
II		April	370	2840, 41, 37	8/30
III		August	16	40, 28, 26	10/29
IV		November	520	4100, 12, 11	8/26
	CLUPEIDS
II		April	32	67, 62, 32	6/30
III		August	106	660,325, 80	12/29
IV		November	27	79, 62, 50	10/26
	CARANGIDS
II		April	55	280,260,160	21/30
III		August	141	855,510,366	17/29
IV		November	298	2554,537,486	14/26
	SCOMBRIDS
II		April	16	67, 16, 10	7/30
III		August	7	23, 15, 14	13/29
IV		November	13	24, 23, 19	7/26
	BARRACUDAS
II		April	10	44, 17, 10	11/30
III		August	11	20, 20, 17	8/2
IV		November	16	58, 24, 16	8/26

A number of species of anchovies appeared in small quantities in all of the surveys. The few large catch rates obtained were the Pacific anchoveta Cetengraulis mysticetus.

The thread herring dominates the clupeid catches, but with some round herring, Etrumeus teres caught together with scad in deeper waters in the north. Thread herring appears to have had the highest availability in the August survey. Carangids gave relatively high catch rates both in August and November with the Pacific bumper contributing most of the rates exceeding 100 kg/hour, while a few consisted of bigeye scad and lookdowns. Nearly all carangids were caught in water depth of less than 40 m. The catch rates of the sierra and the barracuda are, as shown in the table, considerably lower than those of the other groups with no trend between the surveys.

Biomass estimates

In addition to providing observations for description of the distribution of pelagic fish the acoustic integration system also allows assessments to be made of the absolute abundance of the fish expressed in weight of standing biomass. The methodical basis for this is briefly discussed in Chapter 1 above. Table 3.1.2 presents the estimates of small pelagic fish for each of the surveys and for the shelf south and north of Buenaventura.

Table 3.1.2 Colombia. Estimated biomass of pelagic fish by surveys and parts of the shelf 1 000 tonnes.
Survey		Buenaventura south	Northern shelf	Total
II	April	79	8	87
III	August	30	55	85
IV	November	37	21	58

Many of the areas of dense recordings especially of engraulids and clupeids were located close inshore and reaching the inshore operational limit of the vessel. Assuming a similar density to extend inside the limit of the survey area and about half way to the shore in these uncovered parts the biomass estimates for anchovies and thread herring have been raised by the appropriate proportion of the uncovered shelf. There are considerable variations in the biomass estimates between surveys and areas and these can in part have been caused by movements of fish in and out of the area covered. A substantial part of the high estimates for the northern shelf in August derive from recordings in deeper waters of hairtails off the Gulf of Cupica. A further separation of this group of small pelagic fish can be made based on analysis of the acoustic distribution charts and the trawl sampling programme. Taking the mean of the three survey estimates this gives the following rough assessments of stock biomass for the whole Colombian shelf: thread herring 29 000 tonnes, anchovies 9 000 tonnes, carangids with some sierra, barracuda and hairtails 39 000 tonnes.

3.1.2 Demersal resources

The main source of data for the analysis of the demersal resources is from the random bottom trawl stations. For the surveys in Colombia this material consists of 23,23, and 25 trawl hauls from the three coverages. The analysis below was carried out for two depth strata: 0-50 m and 50-100 m, for each of the surveys. For the deeper waters, where the number of hauls are few, the data from all surveys were pooled together and analysed by the following depth strata: 100-200 m and 200-500 m. Below, only the highlights from the analysis with the main species or species groups are commented upon in the text. The complete results from the analysis are included in the Data File.

Demersal fish

The main demersal species in Colombian waters are butterfishes, Peprilus medius and P. snyderi, rose threadfin bass Hemanthias signifer, catfish Bagre panamensis, lizard-fish Synodus evermanni spotted rose snapper Lutjanus guttatus, Panama grunt Pomadasys panamensis and widespur seabass Diplectrum euryplectrum.

The main species caught in the 0-50 m bottom depth zone are catfish, lizardfish, spotted rose snapper, panama grunt, threadfins Polynemidae, and barracuda.

The main species in the 50-100 m bottom depth stratum are butterfish, threadfin bass, lizardfish, and goatfish.

In the 100-200 m bottom depth range the dominating species are the argentine Argentina aliceae and seabasses Hemanthias signifer and Diplectrum euryplectrum.

Catch composition

As most of the bottom trawl hauls are randomly localized for purpose of swept area estimates, they will not be representative for an aimed fishery at targeted species and locations. The highest catches, however, might be representative for a fishery and the mean catch might serve as indicators of minimum catch rates in a wide scale fishery.

Table 3.1.3 shows the mean catch rates by surveys in kg/hour and the total catch distribution by size classes for the main species of demersal fish in Colombian waters.

Table 3.1.3 Colombia. Mean catch rates of main species and catch distribution by size classes of all hauls.
Species/ survey	Mean rate kg/hour	Number of hauls in catch groups						Rate of occurrence
		1-30kg	30-100kg	0.1-0.3t	0.3-1t	1-3t	>3t
Butterfish
II-IV	67	14	2	1	1		1	19/63
Rose threadfin bass
II-IV	16	11	3	3	1			18/63
Catfish (Bagre panamensis)
II-IV	13	10	2					12/63
Spotted rose snapper (Lutjanus guttatus)
II-IV	7	18	2	1				21/63
Panama grunt
II-IV	6	22	4					26/63
Spotted lizardfish
II-IV	9	42	3	1				46/63
Widespur seabass
II-IV	6	5	2	1				8/63
Goatfish (Pseudupeneus grandisquamis)
II-IV	5	31	3					34/63

In order to provide information which relate to the groups which are of existing or potential commercial interest the catch data relating to the well known “commercial” families have been analysed separately as shown in Table 3.1.4.

Table 3.1.4 Colombia. Mean catch of commercial demersal families by surveys and mean of total hauls.
Family	Mean catch rates (kg/hour)
	Survey II	Survey III	Survey IV	Total
Butterfish	162	6	3	67
Snappers	18	2	4	9
Groupers	20	37	9	30
Grunts	5	4	8	6
Sharks	19	17	10	17

Although it is appropriate to keep in mind that this trawl survey programme will not simulate “commercial” catch rates the generally very low rates in Table 3.1.4 must be said to reflect a poor fauna of commercial fish.

Biomass estimates

In the Data File, Annex 8, are given estimates of fish density by depth stratum. By multiplying these densities with the area of the shelf, given in Table 2.1, estimates of standing biomass are obtained by surveys and species or species groups. These estimates are presented in Table 3.1.5.

Table 3.1.5 Colombia. Estimates of biomass of demersal fish on the shelf (0-200m) by main groups and surveys. 1000 tonnes.
	Survey II	Survey III	Survey IV	All surveys
Snappers	3.5	0.3	0.8	1.5
Seabasses	4	7	2	6
Grunts	1	1	1.5	1.2
Butterfish	30	1	0.6	12
Sharks	3.5	3	2	3
Other demersal fish	23	25	24	24
Total demersal fish	65	37	31	48

Since these demersal fish tend to be long lived species one should not expect any true seasonal variation in biomass and the best estimates are probably obtained by pooling the data from all surveys. The total “stock biomass” for all five groups of the more commercially interesting demersal fish is thus estimated to 24 000 tonnes. Butterfish represents half of this. “Other” demersal fish of little or no commercial interest such as lizardfish, goatfish etc. doubles the total biomass to 48 000 tonnes for all demersal fish.

Shrimp

The nylon shrimp Heterocarpus vicarius, the kolibri shrimp Solenocera agassizii and crystal shrimp Penaeus brevirostris were the most abundant shrimp species, all in the depths beyond 50 m. Various penaeid shrimps inhabit the 0-50 m bottom depth range, and among these, Xiphopenaeus riveti was the only with catches exceeding 5 kg/hour.

Table 3.1.6 shows the mean catch rates, the three highest catch rates and the rate of occurrence, expressed as the number of hauls were the species is present over the total number of trawl hauls in the relevant depth stratum.

Table 3.1.6 Colombia. Catch rates in kg/hour by main species of shrimp. Mean rates, highest rates and rate of occurrence.
Species	Mean rate	Highest rates	Rate of occurrence
Nylon shrimp	12 *	160, 148, 68	4/32
Kolibri shrimp	2.4*	31, 17, 10	9/32
Chrystal shrimp	1.6$	22, 2, 1	3/16
Pacific seabob	2.4#	40, 25, 20	8/40

* Mean of 32 hauls in the 150-500m bottom depth range.
# Mean of 40 hauls in the 0-50m bottom depth range.
$ Mean of 16 hauls in the 50-100m bottom depth range.

Squid

Dart squid Loliolopsis diomedeae appeared in the catches in somewhat deeper hauls, 50-100 m and beyond in various locations, but especially between Pta. Guascama and Buenaventura. The coverage in this depth range was not very extensive, but in the April survey the mean catch of this species in six hauls with catch out of a total of nine trials was 47 kg/hour with a maximum rate of 190 kg/hour. The data from Panama indicate a clear annual cycle in the presence of this squid with a maximum in the first part of the year and nearly absence from August to November. A similar seasonal change is likely also for Colombia. The dart squid can only be fished in bottom trawl during daytime as it lifts off the bottom at night.

3.1.3 Overview of survey results and estimates of standing biomass of the resources

The following groups of resources were identified and will be discussed:

Small pelagic fish was found well inshore above the thermocline and distributed in patches along the coast and with the densest aggregations between Pta. Guascama and Buenaventura. The main components were thread herring, anchovy, carangids mostly bumper with some lookdown and bigye scad, and smaller amounts of sierra and barracuda.

Demersal fish was found on trawlable ground mostly in the 20-100 m depth range along the coast and with highest catch rates in the south. About half of the catches consisted of small sized species of no commercial interest. Among the potentially commercial fish butterfish was most common, followed by mostly small sized seabasses, sharks, snappers and grunts. The bottom trawl hauls in deeper waters in the north gave some high catch rates of hairtails and argentine.

Dart squid was caught in the 50-100 m range especially in the south. The survey results are restricted to information on catch rates. They reached a mean of abt. 50 kg/hour with maximum nearly 200 kg/hour.

Also for shrimps only catch records are presented, but survey results may represent an opportunity to study shrimp by-catches. The catch rates for nylon shrimp in the north reached about 150 kg/hour.

The total biomass is thus estimated at abt. 100 000 tonnes and this gives a mean density for the shelf (0-200 m) of 18 tonnes pr nm². If the estimated amount of non-commercial demersal fish of abt. 24 000 tonnes is included, the density is 22 tonnes/ nm². This is a level of density found in many tropical countries with similar ecological conditions. Detailed information on the history of existing fisheries is necessary in order to discuss the potentials of these resources.

Table 3.1.7 Colombia. Estimated standing biomass by resource groups. Tonnes.
Small pelagic
	Thread herring		29000
	Anchovy		9000
	Carangids with		39000
		Sierra
		Barracuda
		Hairtails
	Total			77000
Demersal
	Butterfish		12000
	Sea basses		6000
	Sharks		3000
	Snappers		2000
	Grunts		1000	24000

3.1.4 Comments to the findings

Since 1969, a considerable number of exploratory and special fishing surveys for shrimp, pelagic and bottom fish have been made on the Pacific coast of Colombia. The derived estimated levels of potentials for small pelagic fish are 35 000 tonnes for thread herring and 15 000 tonnes for Pacific anchoveta. These are high compared to the biomass estimates from the surveys, but landing statistics show two years of catches which may well correspond to potentials at this level, 1980 with 15 000 tonnes and 1981 with 25 000 tonnes for the two species combined. In 1983 catches declined below 1 000 tonnes for reasons other than resource availability. The reported landings of carangids are abt. 1000 tonnes or lower and a comparison with the biomass estimate from the survey indicates a potential for increase. The total landings of demersal fish have ranged between about 2 500 and 3 700 tonnes over 1985-1987. A comparison with the survey biomass estimate for this group indicates a potential for increase for some groups of these resources.

Catch rates obtained in shrimp surveys in 1980 and 1983 for kolibri- and nylon shrimps were similar to those shown by the “DR. FRIDTJOF NANSEN” trials. Shelf squid has been fished over the last year by one vessel with total annual landings up to 400 tonnes.

3.2 THE GULF OF PANAMA

3.2.1 Small pelagic fish
3.2.2 Demersal resources

The Panama shelf can conveniently be separated into two main parts: the wide and extensive Gulf of Panama and the western coast with the Gulfs of Coiba and Chiriqui. The Gulf of Panama is known as an important fishing area where as described in Chapter 2.1, seasonal upwelling and perhaps also river runoffs creates conditions for productivity. Seasonality is evident in the hydrographic environment especially in the deeper parts of the gulf with fluctuations in temperature and oxygen content which affects the fish resources. But there are also seasonal changes in the surface layers with a lifting and weakening thermocline in the upwelling season in winter which may affect the fish.

3.2.1 Small pelagic fish

Distribution

Figure 3.2.1 shows the distribution of small pelagic fish as observed with the acoustic integration system in the surveys of February, May, August and November 1987. For the Gulf of Panama a general feature of these charts is that aggregations of high densities are found throughout the year around the shores of the gulf and particularly in the northeastern, northern and northwestern parts. In the central and deeper parts, fish was only recorded in May and August, with nearly complete absence in February and November probably caused by the low oxygen levels near the bottom in this season. The assemblage of fish above the thermocline and which seems to prefer depths of less than 50 m was dominated by thread herring Opisthonema libertate and anchovies Anchoa and Cetengraulis species found in school areas in which schools of bumper Chloroscombrus orqueta were usually also frequent. Frequent predators in these school areas were sierra Scomberomorus sierra, barracuda Sphyraena ensis, sharks and various demersal fish. In all of the surveys such school areas were found in the Bahia de Panama where birds were abundant and the schools often were breaking the surface. Aggregations were usually also found east of the Pearl Islands.

The fauna below the thermocline in the middle offshore part of the gulf, present in significant quantities only in May and August, was dominated by scads Decapterus macrosoma mixed with some round herring Etrumeus teres and various demersal fish.

Catch compositions

Additional information on the composition and distribution of the pelagic fish is contained in the results of the fishing experiments. It must be noted, however, that most of the fishing with bottom trawl formed part of the programme for the swept area biomass estimation of demersal fish and for this purpose the trawl stations are positioned more or less randomly and with no intention of obtaining high catch rates. Pelagic types of fish often formed substantial parts of the catches in these hauls and otherwise fishing for identification and sampling of pelagic types of fish was made both with demersal and mid-water trawls. These data can add to our picture of the general occurrence and composition of the various groups and species, but they must be interpreted with caution.

Figure 3.2.1 Panama. Fish distribution as recorded by the acoustic system, by surveys. (Survey 1)

Figure 3.2.1 Panama. Fish distribution as recorded by the acoustic system, by surveys. (Survey 2)

Figure 3.2.1 Panama. Fish distribution as recorded by the acoustic system, by surveys.(Survey 3)

Figure 3.2.1 Panama. Fish distribution as recorded by the acoustic system, by surveys.(Survey 4)

The catchability of these gears are often highly species and size selective, large sized schooling clupeids such as thread herrings have for instance a very low catchability while anchovy, smaller carangids such as bumper and scads and more solitary species such as sierra and barracudas are more easily caught both at the bottom and in mid-water.

Complete catch records and various types of processed outputs giving catches by groups, species and surveys are available in the Data File to this report. Here we will only show some brief extracts of the catch data.

Table 3.2.1. shows the mean catch rates in kg/hour for the main groups/species of pelagic fish for the Gulf of Panama by surveys. The highest catch rates for engraulids were of Pacific anchoveta, Cetengraulis mysticetus and gulf anchovy, Anchoa helleri, but an additional ten species of the genus Anchoa were caught. The highest combined catch rates and rate of occurrence was in August, but one should recall that trawl is not an effective gear for this species and part of the stocks may have escaped one or more of the surveys in the inshore shallow waters.

Table 3.2.1. Gulf of Panama. Catch rates in kg/hour by main groups/species of pelagic fish by surveys. Mean rates, three highest rates and rate of occurrence.
Survey			Mean rate	Highest rates	Rate of occurrence
	ENGRAULIDS
I		Febr.	135	596, 289, 38	7/41
II		May	49	88, 10	2/46
III		Aug.	74	790, 92, 31	15/42
IV		Nov.	33	204, 38, 36	16/40
	CLUPEIDS
I		Febr.	14	31, 21, 17	6/41
II		May	104	319, 261, 209	10/46
III		Aug.	199	1234, 989, 566	22/42
IV		Nov.	23	132, 115, 51	23/40
	ROUND HERRING
II		May	113	209, 95, 35	3/46
III		Aug.	152	566, 223, 103	6/42
	CARANGIDS
I		Febr.	247	1440, 1008, 720	20/41
II		May	316	1826, 1216, 1076	24/46
III		Aug.	864	8123, 5341, 4280	32/42
IV		Nov.	207,	2733, 581, 492	30/40
	BUMPER
I		Febr.	250	1440, 945, 406	17/41
II		May	182	898, 307, 206	10/46
III		Aug.	799	5228, 2378, 1409	15/42
IV		Nov.	256	2634, 480, 374	18/40
	SCAD
II		MAY	516	1826, 154, 62	4/46
III		Aug.	2088	8123, 4280, 1119	7/42
IV		Nov.	105	560, 35, 24	6/40
	SCOMBRIDS
I		Febr.	35	149, 21, 18	6/41
II		May	25	64, 17, 12	4/46
III		Aug.	21	97, 38, 37	16/42
IV		Nov.	14	51, 48, 16	13/40
	BARRACUDA
II		May	19	34, 22, 16	5/46
III		Aug.	34	137, 43, 38	9/42
IV		Nov.	23	136, 48, 23	12/40

The thread herring is the dominating clupeid in the shallow water assemblage with the highest catch rates and availability in the August survey. This species has undoubtedly a very low catchability with trawl. That does not seem to be the case for the round herring which was caught in some quantities in the deeper waters, 70-110 m of the gulf in May and, with highest rates, in August.

The carangids with a number of different species form the largest component of the catches of pelagic fish in the gulf. In the shallow water assemblage the Pacific bumper is by far the most common and abundant species. The highest catch rates were obtained in August and November. Other important forms in this group with some rates exceeding 100 kg/hour were lookdowns, while various jacks, Caranx, Hemicaranx and Oligoplites species usually did not reach that level. An occasional catch of fortune jack, Seriola peruana exceeded 1 tonne/hour. In the deeper waters of the shortfin scad, Decapterus macrosoma was caught with high rates, up to abt. 8 tonnes/hour in August, but with lower rates in May and November.

The catches of the mackerel group consisted mainly of the sierra, but with an occasional catch of black skipjack, Euthynnus lineatus. The mean catch rates were low throughout, abt. 15-35 kg/hour, but the rate of occurrence was markedly higher in August and November, probably an effect of the higher availability of their prey species at this time.

The barracuda played much the same role as the scombrids in the catches with increasing occurrence in the last half of the year.

Biomass estimates

The estimates of standing biomass from the acoustic integration of the inshore areas are shown in Table 3.2.2 by surveys and for the groups engraulids and clupeids, PELAGIC I, and carangids and others, PELAGIC II, separately.

Table 3.2.2 Gulf of Panama. Estimates of standing biomass of pelagic fish by surveys and groups. 1 000 tonnes. Inshore areas.
Survey		PELAGIC I	PELAGIC II	TOTAL
I	Febr.	61	70	131
II	May	90	37	127
III	Aug.	139	87	226
IV	Nov.	77	93	170

The high density areas of the PELAGIC I group were often located inshore and extending onto the inner limit of the survey operation leaving uncovered parts of the distributions further in. In such cases a correction has been made assuming a mean density continuing about halfway to the shore.

For both groups the highest densities were found in the August survey. The variation between surveys may in part derive from incomplete coverage, a higher part of the biomass may in some surveys have been distributed in the shallow inshore waters not covered or represent other types of effects relating to survey methodology such as migration into and out of the gulf. The change in biomass could, however, also be a true seasonal variation caused by an annual production cycle deriving from the seasonal upwelling and the short life span of many of the small pelagic fish. The trend of variation in the acoustic biomass data is confirmed by the similar trend in the catch data for the main groups and species as discussed above. For the purposes of stock assessments and potentials it is proposed to use the mean of the biomass estimates for the August and November surveys. For the deep water species round herring and scad it is assumed that the best stock estimate was obtained by the August survey.

Some further separation of the biomass estimates of these two groups of small pelagic fish by stocks or sub-groups can be made on the basis of the acoustic distribution charts and the catch data although with reduced precision. The resulting stock biomasses based on a mean of surveys III and IV are:

Engraulids:	28 000 tonnes
Clupeids:	76 000 tonnes.

The round herring in the deep water assemblage can be estimated separately. This species occurs together with scad and being available to bottom trawl during the day is likely to be underestimated by the acoustic system. An acoustic assessment gives 48 000 tonnes for August and 55 000 tonnes for November for both species. By catch proportion the round herring represents abt. 8% of this biomass or abt. 4 000 tonnes. A biomass estimate based on a swept area analysis of the trawl hauls in this deeper shelf gives abt. 5 000 tonnes.

Separate estimates can be made for the scad, Decapterus macrosoma both acoustic and swept area as for round herring: These are 51000 tonnes for the acoustic and 67 000 tonnes for the swept area data. The high catch rates in bottom trawl indicate that this species will be underestimated by the acoustic system.

Among the shallow water carangids the bumper is as shown above the dominating species. A further separation of biomass by species could be attempted using the proportions in the catches and assuming the same catchability. Such an exercise is perhaps not of special fishery interest and for this group only a combined assessment will be presented. These are 85 000 tonnes for August and 87 000 tonnes for November.

It is doubtful whether the barracudas and scombrids are properly covered and sampled in the survey. Their combined proportion of PELAGIC II fish in the catches in August and November were 2.4% and 7.0%, and biomass estimates based on these gives 2 000 tonnes and 6 500 tonnes. These should be considered as minimum stock levels.

3.2.2 Demersal resources

The main source of data for the analysis of the demersal resources is from the random bottom trawl stations carried out. For the surveys in Panama this material comprise 24, 35, 29 and 31 trawl hauls from the four coverages. In the analysis below the datasets have been analysed by depth strata: 0-50 m, 50-100 m, 100-200 m for each of the surveys. For the deeper waters, where the number of hauls are few, the data from all surveys have been pooled together and analysed by the following depth strata: 150-200 m, 200-300 m. 300-400 m and 400-500 m. Below, only the highlights from the analysis, with the main species or species groups, are commented upon in the text. The complete results from the analysis are included in the Data File.

The demersal fish fauna of the Gulf of Panama can be grouped by three main habitats:

1) the nearshore habitat from the shore to about 50 m bottom depth,
2) the offshore habitat, from about 50 m to the shelf edge and
3) the slope habitat, from the shelf edge and into deep waters.

Demersal fish

The main demersal species in the Gulf of Panama are butterfishes, Peprilus medius, P. snyderi, rose threadfin bass Hemanthias signifer, Pacific red snapper Lutjanus peru, lizardfish Synodus evermanni and widespur seabass Diplectrum euryplectrum. Frequent in the catches, but with less abundance, were Panama grunt Pomadasys panamensis, yellow bobo Polydactylus opercularis and bigscale goatfish Pseudupeneus grandisquamis.

The 0-50 m bottom depth zone is relatively poor in demersal fish, compared to the deeper stratum. The main species in the shallow waters are butterfish, spotted rose snapper Lutjanus guttatus and the Panama grunt.

The main species in the 50-100 m bottom depth stratum are butterfish, lizardfish, sea-robin Prionotus quiescens and the widespur seabass.

In the 100-200 m bottom depth range the dominating species are the argentine Argentina aliceae, deepwater seabasses Hemanthias signifer, and Pronotogrammus multifasciatus and Pacific red snapper Lutjanus peru. Notable in the catches were also lizardfish, widespur seabass and fortune jack Seriola peruana. The mean density of fish recorded in this bottom depth stratum is considerable higher than in the shallower waters, but as the total number of hauls carried out in the stratum are few, they may not be representative for a true average.

The dominating fish species on the slope beyond 200 m bottom depth is the argentine. Only 10 bottom trawl hauls were made on the slope during the programme.

Catch composition

As most of the bottom trawl hauls are randomly localized for purpose of swept area estimates, they will not be representative for an aimed fishery at targeted species and locations. The highest catches, however, might be representative for a fishery and the mean catch might serve as indicators of minimum catch rates in a wide scale fishery.

Table 3.2.3 shows the mean catch rates in kg/hour and the catch distribution by size classes for the main species of demersal fish in the Gulf of Panama by surveys and by total hauls.

Table 3.2.3 Gulf of Panama. Mean catch rates and catch distribution by size classes of all hauls.
Species/ survey	Mean rate kg/hour	Number of hauls in catch groups						Rate of occurrence
		1-30kg	30-100kg	0.1-0.3t	0.3-1t	1-3t	>3t
Butterfish
I-IV	96	26	8	10	3	2	1	50/122
Rose threadfin bass
I-IV	77	11	2	1	1		1	16/122
Pronotogrammus multifasciatus
I-IV	226	1	2				1	4/122
Pacific red snapper
I-IV	54	5	2				1	6/122
Spotted rose snapper (Lutjanus guttatus)
I-IV	11	15	4	2	1			22/122
Spotted lizardfish
I-IV	29	42	6	5	2	1		56/122
Widespur seabass
I-IV	16	15	9	6	1			31/122
Panama grunt
I-IV	10	25	4	5				34/122
Yellow bobo
I-IV	9	24	7	1	1			33/122
Bigeye goatfish
I-IV	2	31	4					34/122
OFFSHORE SPECIES IN DEEP WATER HAULS 150-400m
Silver smelt
I-IV	1732	1	0	3	0	3	2	9/16

Butterfish is seen to be one of the most common species, with both high catch rates and a presence reaching abt. 40% of all catches. Several catch rates exceeded 1 tonne/hour. The spotted rose snapper was more common than the red snapper, but catch rates were medium or low. Argentine gave some high catch rates in offshore waters.

Catch rates for the commercially more interesting groups are summarised in Table 3.2.4.

Table 3.2.4 Panama. Mean catch rates by surveys and by total hauls for the main commercial groups.
Family	Mean catch rates (kg/hour)
	Survey I	Survey II	Survey III	Survey IV	Total
Snappers	0	198	36	2	67
Groupers	4	1096	39	2	324
Grunts	23	80	86	21	55
Butterfish	95	189	68	27	96
Sharks	10	18	8	8	13

The high rates for the groupers result from a few very large catches of small sized sea-basses from deep water. The variation in catch rates between surveys may partly be an effect of different coverage, but is also thought to reflect the depopulation of the mid shelf during winter when upwelling reduces the oxygen content of the deeper water masses of the gulf. The best season for demersal fish thus seems to be April-August.

Biomass estimates

In the Data File, Annex 8, are given estimates of fish density by depth strata. By multiplying these densities with the area of the shelf, given in Table 2.1, estimates of standing biomass are obtained by surveys and species or species groups. These estimates are presented in Table 3.2.5.

Table 3.2.5 Gulf of Panama. Estimates of biomass of demersal fish on the shelf by main groups and surveys. 1 000 tonnes.
	Survey I	Survey II	Survey III	Survey IV	All surveys
Snappers	.1	4	10	0.7	6
Groupers	1.1	12	11	0.4	9
Grunts	7	22	24	6	22
Butterfish	26	52	19	7	42
Sharks	3	5	2	2	5
Other demersal fish	16	115	84	18	126
Total demersal fish	53	210	150	34	210

There is a considerable variation between surveys and this is, as discussed above, likely to be an effect of the fluctuations of the environmental conditions over the mid and outer shelf. The best estimates of stock biomass for these groups are therefore thought to be obtained by taking the means of surveys II and III. These are (1000 tonnes):

Snappers	7
Groupers	12
Grunts	23
Butterfish	36
Sharks	4
Other demersal fish	98
Total demersal fish	180

The butterfish comes out with the highest biomass followed by grunts, Pomadasys and Orthopristis species. Various groupers make up abt. 12 thousand tonnes and snappers 7 thousand tonnes. The estimates of sharks varies between 2 and 5 thousand tonnes with a mean of 4 thousand tonnes. The “other demersal fish group” which make up more than 50% of the total estimate, consists mainly of low value fish such as lizardfish, thread-fins and searobins.

During the second survey 12 trawl hauls were made close to the shelf edge. A few of these gave very high catches of deep water seabasses, snapper and argentine. The sampling in the area is, however, not sufficient to allow these samples into the swept area analysis, and they are not included. The catches might indicate, however, that there is a high production zone in the deeper waters, but quite narrow in width of the shelf. A similar observation was made offshore in Nicaragua, but there the area was wider and more sampling was carried out. The catches that have been excluded from the analysis are of Pacific red snapper, rose threadfin bass and another deep water bass Pronotogrammus multifasciatus. One catch of each of these, all exceeding 3 tonnes/hour in catch, was omitted from the analysis.

All pelagic fish and argentine have also been kept out of the swept area analysis.

Shrimp

The shrimps found in deeper waters beyond abt. 150 m of depth in the region are the nylon shrimp Heterocarpus vicarius and the colibri shrimp Solenocera agassizii. Various penaeid shrimps inhabit the 0-50 m bottom depth range of which Penaeus brevirostris, Penaeus occidentalis and Penaeus californiensis were most frequent in the catches.

Some trawl hauls were made on the well known ground for deep water shrimp at 200-300 m in the slope off Pta. Mala in order to test the availability of the shrimp there. In shallow waters no special effort was made to survey the shrimps, and the catches there should be considered incidental. Table 3.2.6 shows the catch rates as the means of all hauls in the respective depth strata and also the highest catch rates obtained. The high rates in deep waters are at a similar level as those obtained in previous exploratory surveys.

Table 3.2.6 Gulf of Panama. Catch rates in kg/hour by main groups or species of shrimp. Mean rates, highest rates and rate of occurrence.
Species	Mean rate	Highest rates	Rate of occurrence
Nylon shrimp	513*	4750, 1920, 840, 420	8/16
Solenocerid shrimp	14*	68, 37, 28, 24	11/16
Penaeid shrimps	2.7#	25, 22, 13, 9	41/68

* Mean of 16 hauls in the 150-500m bottom depth range.
# Mean of 68 hauls in the 0-50m bottom depth range.

Shelf squids

Two species of loliginid shelf squids are found in the survey area, the dart squid Loliolopsis diomedeae and the Panama brief squid Lolliguncula panamensis. They are similar in behaviour being semipelagic species aggregating near the bottom during the day, but dispersing into the water column at night. The dart squid was by far the most common and was taken in significant catches in many parts of the survey area. The brief squid was less frequently caught and only in minor amounts. Only dart squid is therefore included in the descriptions of shelf squid resources in the following. An analysis of the depth distribution by weight of all trawl hauls with more than 5 kg of catch of dart squid in the entire survey area, about 140 hauls showed that abt. 93% derived from the depth range 50-150 m. The depth range 50-100 m accounted for abt. 75%. The rate of occurrence of this species will therefore be measured as hauls with catch in the depth range 50-150 m as part of the total number of daylight hauls in this range.

In the Gulf of Panama the dart squid appeared to be distributed in special areas of high abundance in 50-100 m of depth southeast and south of the Pearl Islands and in the southeast part of the gulf from Bahia Pinas up along the coast towards the Pearl Islands. Good catches were made in this area both in February and in May.

Table 3.2.7 shows the catch rates and rates of occurrence of the dart squid for each survey. During the two first surveys (February and May) the species occurred in most of the catches in the 50-100 m bottom depth range. In the two last surveys, however, (August and November) the squid was virtually absent from the catches, demonstrating a clear yearly life cycle.

Table 3.2.7. Gulf of Panama. Catch rates of dart squid in the 50-150 m depth range by surveys. Mean rates, three highest rates and rate of occurrence. Kg/hour.
Survey		Mean rate	Highest rates	Rate of occurrence
I	Febr.	290	1470, 260, 110	7/8
II	May	490	5250, 220, 180	12/20
III	Aug.	0	0,	0/12
IV	Nov.	4	7, 4, 3	4/15

Estimates of biomass

Being a semi-pelagic species and with no swim-bladder the squid is difficult to quantify by either swept area or acoustic methods. During the first survey considerable amounts of squid were located in the pelagial in the eastern part of the gulf. As the squid only form faint traces on the echosounder and its target strength is unknown, the acoustic method is not applicable. The swept area estimates, covering only a depth slice of 6 m off the bottom, will on the other hand give underestimates. In Table 3.2.8 estimates are given based on the swept area method. These are not to be interpreted as full estimates of the standing stock, but more as a demonstration of the minimum level stock level, as it represents only the part close to the bottom.

Table 3.2.8 Gulf of Panama. Estimates of biomass of demersal squid by the swept area method. 1 000 tonnes.
Survey I	Survey II	Survey III	Survey IV
33	30	0	0.4

The estimates from surveys I and II agree fairly well and indicate a stock biomass of 30 000 tonnes for the gulf.

Giant squid, Dosidiscus gigas

This species is known to occur over the slope and over deeper waters offshore in this region. It was caught as incidental by-catch in 24 bottom trawl hauls in the whole survey with catch rates ranging up to abt. 90 kg/hour mostly from depths of 200-400 m and both by day and at night. Such incidental catches were taken on the slope off the Gulf of Panama in surveys I and II. In survey II a haul with the mid-water trawl in this area gave a catch of approximately 0.5 tonnes of the species near the shelf edge.

The trawl is, however, not an appropriate gear for catch of this species and a small programme of light attraction and jigging with 2-3 hand lines was attempted. The effort spent on this type of testing was limited to a few tests in unfavourable weather conditions in survey I and some tests in survey III when a few small specimens were caught. From the survey one can not draw any conclusions regarding a possible existence of a resource of this species off Panama. It was proved to be present and the indications are that the most interesting areas are the slope regions off Pta. Mala and west of Bahia Pinas.

3.3 PANAMA WEST COAST, THE GULFS OF COIBA AND CHIRIQUI

3.3.1 Small pelagic fish
3.3.2 Demersal resources

As shown in Chapter 2.1 above the hydrographic environment in the western gulfs is far more stable than that in the Gulf of Panama with only minor variations in the surface temperature and small changes in the depth and strength of the thermocline through the year. Fisheries are less developed in this western area.

3.3.1 Small pelagic fish

Distribution

The distribution as recorded with the acoustic system is shown in Figure 3.2.1. The general impression is that the larger parts of this western Panamanian shelf was almost without any recordings of fish in all of the surveys. Aggregations of schooling pelagic fish were only located close inshore and the school areas were in most cases quite small. This inshore assemblage consisted mainly of the same species as that in the Gulf of Panama: various species of anchovies, thread herring, different carangids and with barracudas as predators.

Catch compositions

This poorer fauna as compared with the Gulf of Panama is also reflected in the catches. Table 3.3.1 shows the catch rates and rates of occurrence for the main groups. Rates for both anchovies and clupeids were low throughout. Carangids showed somewhat higher availability in May and August, although the May rate is influenced by a single catch of bigeye scad which exceeded 3 tonnes/hour. Low rates of shortfin scad, Decapterus macrosoma were obtained in deeper waters together with round herring representing a westward extension of their main distributional area in the Gulf of Panama.

Table 3.3.1. Western Panama. Catch rates in kg/hour by main groups/species of pelagic fish by surveys. Mean rates, three highest rates and rate of occurrence.
Survey			Mean rate	Highest rates	Rate of occurrence
	ENGRAULIDS
I		Febr.	167	332, 2	2/14
II		May	18	48, 37, 36	8/25
III		Aug.	30	90, 41, 21	7/30
IV		Nov.	9	35, 8, 3	6/15
	CLUPEIDS
I		Febr.	35	57, 13	1/14
II		May	14	26 16, 16	5/25
III		Aug.	22	104, 25, 20	10/30
IV		Nov.	16	45, 10, 5	4/15
	CARANGIDS
I		Febr.	96	446, 14, 9	5/14
II		May	350	3396, 273, 237	12/25
III		Aug.	40	193, 72, 69	16/30
IV		Nov.	24	66, 56, 24	8/15
	SCOMBRIDS
I		Febr.	4	4	1/14
II		May	30	67, 51, 48	6/25
III		Aug.	8	15, 13, 11	9/30
IV		Nov.	8	13, 11, 1	3/15
	BARRACUDA
I		Febr.	8	9, 7	2/14
II		May	139	464, 242, 103	6/25
III		Aug.	124	597, 108, 92	7/30
IV		Nov.	6	13, 5,4	4/15

Biomass estimates

Table 3.3.2 shows the biomass estimates from the acoustic integration system.

Table 3.3.2 Western Panama. Estimates of standing biomass of pelagic fish by surveys and groups. 1000 tonnes.
Survey		PELAGIC I	PELAGIC II	TOTAL
I	Febr.	26	13	39
II	May	7	11	18
III	Aug.	26	20	46
IV	Nov.	20	9	29

The results confirm the impression from the distribution charts and the fishing experiments that the western gulfs represent an area of sparse pelagic resources. Except for May the totals show little variation between surveys. For purposes of stock assessment it is proposed to use the mean of the August and November values. Separation by groups must be restricted to the following as rough assessments of available biomasses:

Engraulids	9000t
Clupeids mostly thread herring	14000t
Shallow water carangids	15000t

3.3.2 Demersal resources

For the western part of Panama, from Pta. Mala and westwards the data for swept area analysis comprise 7, 22, 29 and 19 trawl hauls from the four coverages. In the analysis below the datasets have been analysed by depth strata: 0-50 m and 50-100 m. For the deeper waters, were the number of hauls are few, the data do not allow detailed analysis. Below, only the highlights from the analysis with the main species or species groups are commented upon in the text. The complete results from the analysis are included in the Data File, Annex 8.

The demersal fish fauna of the region can be grouped by three main habitats:

1) the narrow shelf between Pta. Mala and Gulf of Coiba with a relative rich and varied fauna,

2) the Gulfs of Coiba and Chiriqui with an extensive shelf but with poor demersal catches, both qualitatively and quantitatively and

3) the slope, from 100 to 400 m bottom depth. This was generally steep and narrow and was given only a limited input during the surveys.

The main demersal species on the narrow shelf between Pta. Mala and Gulf of Coiba are various snappers Lutjanus guttatus, L. peru, L. argentiventris, L. Colorado, peruvian mojarra Diapterus peruvianus, barracuda Sphyraena ensis, shark Rhizoprionodon longurio and bonefish Albula vulpes. Only 12 hauls were carried out during the programme, but they showed a marked difference both in size and quality composition, compared to the rest of the Panama shelf. This special fauna is probably related to the bottom type, sandy with patches of rocks and corrals. And the apparent absence of any trawl fishery may account for the relatively large size of the specimens.

The main demersal species in the Gulfs of Coiba and Chiriqui are butterfishes, Peprilus medius, P. snyderi, lizardfish Synodus evermanni, S. scituliceps and trashfish as mojarra Diapterus aureolus and toadfish Porichthys nautopaedium. Panama grunt Pomadasys panamensis and goatfish Pseudupeneus grandisquamis occurred in about one third of the catches but at low catch rates only. The species composition in the two western gulfs is quite similar to that of the Gulf of Panama.

Catch composition

Table 3.3.3 shows the mean catch rates in kg/hour and the catch distribution by size classes for the main species of demersal fish on the narrow shelf between Gulf of Panama and the Gulf of Coiba.

Table 3.3.3 Panama between Punta Mala and Gulf of Coiba. Mean catch and catch distribution for the main species in totally 12 hauls.
Species/ survey	Mean rate kg/hour	Number of hauls in catch groups						Rate of occurrence
		1-30kg	30-100kg	0.1-0.3t	0.3-1t	1-3t	>3t
Spotted rose snapper
	255		4			2		6/24
Pacific red snapper
	42	3	2		2			7/24
Amarillo snapper
	30	3	2		2			7/24
Pacific sharpnose shark
	28	2	1		1			4/24
Bonefish (Albula vulpes)
	27	3	1		2			6/24
Chere-chere grunt (Haemulon steindachneri)
	10				1			1/24
Colorado snapper
	8	1	1					2/24

As seen from the table the area gives fairly good catches of commercially valuable fish. The snappers alone sum up to an average catch rate of 335 kg/hour. The trawlable area is, however, quite limited with patches and more extensive areas of rocks and corrals. The area may, however, be suitable for a fishery with lines and traps. There are indications from the surveys that similar aggregations of demersal fish may be found further west along the Panama shelf. Thus in the August survey good recordings were obtained over the Hannibal Bank, but in a pot fishing trial all gear was lost.

Table 3.3.4 shows the catch composition by main species from the Gulfs of Coiba and Chiriqui. Showing close resemblance to the Gulf of Panama, only a few species are of commercial importance. The butterfish is a dominating species, while the other species seem of minor importance, except perhaps the Panama grunt and bigscale goatfish, which has a fairly high rate of occurrence, but with low catch figures.

Table 3.3.4 Panama. Gulf of Coiba and Gulf of Chiriqui. Mean catch and catch distribution for the main species in totally 57 hauls.
Species/ survey	Mean rate kg/hour	Number of hauls in catch groups						Rate of occurrence
		1-30kg	30-100kg	0.1-0.3t	0.3-1t	1-3t	>3t
Butterfish
	20	23	3	1				27/57
Spotted lizardfish
	11	27	2	2				31/57
Shorthead lizardfish
	5	15		1				16/57
Toadfish
	5	26	3					29/57
Mojarra
	5	12	1	1				14/57
Peruvian bass
	3.6	10	2					11/57
Panama grunt
	3	19						19/57
Bigscale goatfish
	3	15	1					16/57
Rose threadfin bass
	2.7	10	1					11/57

The commercially most important species groups have been summed up and their catch rates are presented in Table 3.3.5.

Table 3.3.5 Panama. Gulf of Coiba and Chiriqui. Mean catch rates of total hauls by surveys for the main commercial groups.
Family	Mean catch rates (kg/hour)
	Survey I	Survey II	Survey III	Survey IV	Total
Butterfish	0	50	11	0	20
Snappers	3	4	3	2	3
Groupers	7	27	21	4	16
Grunts	3	2	7	2	4
Sharks	1	10	11	4	8

The main species in the 100-200 m range are the argentine and some shark Mustelus lunulatus. Mean catch rate of argentine is 90 kg/hour from 6 hauls. In the 200-300 m range, where 3 hauls were carried out, two hauls gave catches of Panama hake Merluccius angustimanus with 170 and 22 kg/hour.

Biomass estimates

Estimates offish density by depth strata are given in the Data File, Annex 8. By multiplying these densities with the area of the shelf, given in Table 2.1 estimates of standing biomass are obtained by surveys and species or species groups. These estimates are presented in Table 3.3.6.

The butterfish comes out as the most dominating group on a yearly average, but is caught in two of the surveys only. The “other demersal fish”-group, consisting mainly of noncommercial fish, is the dominating category and represents more than 50% of the total estimate during all surveys. The first and last survey show a considerable lower total estimate compared with the second and third survey. This might partly be due to an incomplete coverage of the shelf during the first and last survey. A yearly average based on the second and third survey only, would be 26 500 tonnes of total demersal biomass.

Table 3.3.6 Panama. Gulfs of Coiba and Chiriqui. Estimates of biomass of demersal fish by commercial species groups and surveys. 1 000 tonnes.
	Survey I	Survey II	Survey III	Survey IV	All surveys
Snappers	0.4	0.5	0.3	0.2	0.4
Seabasses	0.9	3.6	2.7	0.5	2.1
Grunts	0.4	0.2	0.9	0.2	0.5
Butterfish	0.0	6.5	1.4	0.0	2.7
Sharks	0.2	1.3	1.4	0.5	1.1
Other demersal fish	7.1	16.9	17.3	3.2	11.2
Total demersal fish	9.0	29.0	24.0	4.6	18.0

The shelf between Pta. Mala and Gulf of Coiba is not sampled enough to provide estimates by surveys. Total 12 random hauls were set out during the whole year. A swept area analysis based on these gives (shelf 0-100 m 300 nm²):

Snappers:	3400 tonnes
Seabass:	400 tonnes
Grunts:	170 tonnes
Sharks:	600 tonnes

The hauls made off the 100 m bottom depth line are too few to be used in a swept area analysis.

Shrimp

The shrimps caught include the kolibri shrimp Solenocera agassizii beyond 50 m bottom depth and the crystal shrimp Penaeus brevirostris in the 50-100 m bottom depth range. Various shrimps inhabit the 0-50 m bottom depth range of which Penaeus californiensis was the most frequent occurring in the catches.

Table 3.3.7 shows the catch rates.

Table 3.3.7 Panama. Gulfs of Coiba and Chiriqui. Shrimp catch in kg/hour by main groups of species. Mean rates, highest rates and rate of occurrence.
Species	Mean rate	Highest rates	Rate of occurrence
Crystal shrimp	7*	41, 36, 26, 24	27/43
Kolibri shrimp	4#	56, 20, 20, 19	25/54
Other penaeids	2&	14, 11, 9	14/31

* Mean of 43 hauls in the 50-100m bottom depth range.
# Mean of 54 hauls in the 50-300m bottom depth range.
& Mean of 31 hauls in the 0-50m bottom depth range.

Dart squid was found over wide parts of the western gulfs and around Coiba Island mostly in the 50-100 m depth range. As shown in Table 3.3.8 catch rates were considerably lower than in the Gulf of Panama. The coverage in this depth range was, however, poor in some of the surveys.

Table 3.3.8. Western Panama. Catch rates of dart squid in the 50-150 m depth range by surveys. Mean rates, three highest rates and rate of occurrence. Kg/hour.
Survey		Mean rate	Highest rates	Rate of occurrence
I	Febr.	8	10, 6,	2/4
II	May	32	120, 90, 27	9/11
III	Aug.	5	16, 9, 8	10/16
IV	Nov.	25	70, 18, 10	4/8

The biomass estimates from swept area calculations range from a few hundred to 1 600 tonnes. This is surely an underestimate and further investigations are required for the first half of the year, especially for the Gulf of Chiriqui.

3.4 PANAMA, OVERVIEW OF SURVEY RESULTS AND ESTIMATES OF STANDING BIOMASS OF THE RESOURCES

3.4.1 Comments to the findings

The following groups of resources were identified and will be discussed:

Small pelagic fish was found well inshore above the thermocline and distributed in school areas. The highest densities were located along the northern, north-eastern and western coasts of the Gulf of Panama. Only minor aggregations were recorded in the western gulfs. The pelagic fish consisted of thread herring, anchovies, carangids, mostly bumper with some lookdowns and jacks, and sierra and barracudas were present as predators. In addition to this inshore assemblage pelagic fish occurred over the deeper offshore parts of the Gulf of Panama in May and August. These aggregations which were nearly absent in the February and November surveys consisted of scad and round herring.

Demersal fish. Densities of demersal fish were highest in deeper waters 50 m and more, and in the whole area the highest catch rates were obtained in the May-August surveys. Among the groups of potential commercial interest butterfishes dominated followed by grunts, snappers, sea basses and sharks. The fauna was similar in all gulfs, but an offshore component was located in the Gulf of Panama consisting of argentine, small sized sea basses and Pacific red snapper. High catch rates were obtained in one of the surveys in a limited area here. Relatively high densities of demersal fish, mainly snappers, some grunts, sea basses and sharks were found on the narrow shelf between Pta. Mala and the Gulf of Coiba. There were indications that similar aggregations can be found further west, e.g. the Hannibal Bank.

Squid. The dart squid was found in special areas of high abundance in the 50-100 m depth range in the Gulf of Panama. It appears to have an annual cycle of production. In the western gulfs it occurred with far less abundance. Tests for giant squid confirmed its presence, but were inconclusive as fishing trials.

Shrimps. Some tests on the deep water shrimp ground off Pta. Mala confirmed that high catch rates of nylon shrimp can be obtained here. The survey results may otherwise provide data for analyses of by-catches in the shallow water shrimp fisheries.

3.4.1 Comments to the findings

Landings of anchovy for 1987 were 118 000 tonnes and in previous years they have exceeded 200000 tonnes. The biomass estimate from the “DR. FRIDTJOF NANSEN” surveys is thus a gross underestimate, which may mainly be explained by the coastal distribution of these species and the wide shallow areas of the Gulf of Panama. There is also the possibility that a too small part of the estimated total biomass of small pelagic fish has been allocated to anchovy. The landings of thread herring over the last years have been about 10000 tonnes per year which indicate an underexploited stock compared with the biomass estimate. This may relate to the limitation of the purse seine fleet to operate in all but very shallow waters. The catch data on kolibri and nylon shrimps add to the charts of distribution of these species in Panamanian waters. There is no special fishery for dart squid in Panama and this may represent a potentially important resource.

Table 3.4.1 presents a summary of the biomass estimates for the Panama shelf by areas and types of resources. These are likely to lie below the true values for several groups and thus represent minimum levels. The total biomass exceeds 400 000 tonnes and by far the main part, 88% derives from the Gulf of Panama. The main part of this again is from small pelagic fish, the inshore assemblage and the scads and round herring in the offshore part of the gulf. Demersal fish and squid represent abt. 30% of the biomass in the gulf. With a mean density of biomass of 44 tonnes/nm², 56 tonnes/nm² with an estimated biomass of 117 000 tonnes of non-commercial bottom fish included, the Gulf of Panama must be classified as an area of relatively high productivity. This is no doubt related to the phenomenon of seasonal upwelling in the gulf. With 13 tonnes/nm² the western coast lies at a more normal level of tropical shelf productivity. The state of the various stocks and their yield potentials must be considered on the basis of information on the biology of the species, catch statistics from existing fisheries etc.

Table 3.4.1 Panama. Estimated standing biomass by resource groups. Tonnes.
Gulf of Panama
	Small pelagic
		Thread herring	76000
		Anchovy	28000
		Carangids,inshr.	86000
		Barrac.&sierra	4000
		Scad&round herr.	65000
		Total		259000
	Demersal fish
		Butterfish	36000
		Grunts	23000
		Groupers	12000
		Snappers	7000
		Sharks	4000
		Total		82000
		Dart squid		30000
	Shelf Pta.Mala-G.Coiba
		Snappers etc.		5000
	Western gulfs
		Pelagic fish		38000
		Demersal fish		9000
		Total		423000

3.5 COSTA RICA

3.5.1 Small pelagic fish
3.5.2 Demersal resources
3.5.3 Overview of survey results and estimates of standing biomass of the resources
3.5.4 Comments to the findings

The hydrographic environment over the Costa Rican shelf as described in Chapter 2.1 is fairly stable over the year with the thermocline reaching down to 70-80 m at which depth the oxygen content drops below 2 ml/l. Inside the Golfo Dulce this low oxygen level is reached already at 50 m of depth. The surface salinity is low in August and November probably as a result of increased river run-offs. In the westernmost part of the Costa Rican shelf, the Gulfs of Culebra and Papagayo the environmental system is influenced by seasonal offshore winds causing upwelling.

Due to an organizational misunderstanding permits for fish sampling with trawl were only available for surveys III and IV. The data for the two first surveys are therefore incomplete.

3.5.1 Small pelagic fish

Distribution

Figure 3.5.1 shows the fish distribution as observed with the acoustic system in each of the surveys. In Golfo Dulce fish was only recorded near the entrance and at the surface. This is probably related to the low oxygen content of the deeper waters of this threshold gulf. Surface hauls with trawl in November gave, however, ample samples of juveniles of anchovies, hairtails and other fish and the gulf may serve as a nursery area for stocks outside.

Over the open shelf fish was recorded in scattered formations in most surveys and over the deeper parts of the shelf this consisted mostly of demersal fish and hairtails. Dense aggregations were located inshore especially in the Gulf of Nicoya and near its entrance, but often also eastwards to the Bahia de Coronado. The species in this inshore assemblage were largely the same as in Panama, anchovies, clupeids, various carangids, barracuda and sierra, but the relative proportions seem to be different with more large sized carangids and more of the predators including demersal fish. Significant concentrations of pelagic fish were not found in the Gulf of Culebra in any of the surveys, except some schools of small sized fish probably juveniles in survey I, but a deep water assemblage was located on the offshore parts of the shelf off Cape Sta. Helena in the border area between Costa Rica and Nicaragua with partly dense concentrations of hairtails, argentine Argentina aliceae and various seabasses.

Catch compositions

Table 3.5.1 shows the standardized catch rates for the main groups for the surveys in August and November when sampling was normal. The rates both for the engraulid and the clupeid groups were low although one should of course keep in mind the unsuitability of trawl as a gear for capturing these species. The dominating species of anchovy were Anchoa argentivittata, A. ischana and A. curta, and by far the most common clupeid was the yellowfin herring, Pliosteostoma lutipinnis.

Figure 3.5.1 Costa Rica. Fish distribution as recorded by the acoustic system, by surveys. (Survey 1)

Figure 3.5.1 Costa Rica. Fish distribution as recorded by the acoustic system, by surveys. (Survey 2)

Figure 3.5.1 Costa Rica. Fish distribution as recorded by the acoustic system, by surveys. (Survey 3)

Figure 3.5.1 Costa Rica. Fish distribution as recorded by the acoustic system, by surveys.(Survey 4)

Table 3.5.1 Costa Rica. Catch rates in kg/hour by main groups/species of pelagic fish by surveys. Mean rates, three highest rates and rate of occurrence.
Survey			Mean rate	Highest rates	Rate of occurrence
	ENGRAULIDS
III		Aug.	45	177, 145, 77	13/47
IV		Nov.	38	144, 119, 101	20/43
	CLUPEIDS
III		Aug.	58	361, 103, 59	11/47
IV		Nov.	64	200, 197, 144	12/43
	CARANGIDS
III		Aug.	71	599, 246, 221	30/47
IV		Nov.	73	561, 147, 138	22/43
	SCOMBRIDS
III		Aug.	23	102, 36, 30	13/47
IV		Nov.	11	40, 18, 5	7/43
	BARRACUDA
III		Aug.	42	185, 140, 105	19/47
IV		Nov.	11	29, 25, 19	12/43

For the carangids both the catch rates and the rate of occurrence was somewhat higher and the group contained a large number of forms. Lookdowns, Selene peruvianus and S. brevoorti were most common representing 50-60% of the catches. Various jacks, Caranx, Hemicaranx, Carangoides and Oligoplites species represented together abt. 25% and catches of trevally Gnathonodon speciosus and pompanos Trachinotus sp. were made. The size of these carangids was generally larger than that found for this group in the inshore assemblage in Panama.

Scombrids and barracudas had a relatively high availability, especially in the August survey. The sierra dominated, but with a few occasional catches of striped bonito, Sarda orientalis. The barracudas were all Sphyaena ensis.

Biomass estimates

Table 3.5.2 shows the estimates of standing biomass of the inshore assemblage of pelagic fish from the acoustic system by main groups: PELAGIC I corresponding to engraulids and clupeids and PELAGIC II to carangids, scombrids, barracudas, hairtails etc. Sampling for identification of the “acoustic biomass” was not possible during survey II and the proportions found in survey III have been used to allocate the total biomass observed in the second survey.

Table 3.5.2 Costa Rica. Estimates of standing biomass of pelagic fish by surveys and groups. Shallow water. 1 000 tonnes.
Survey		PELAGIC I	PELAGIC II	TOTAL
I	Febr.	35	58	93
II	May	20	50	70
III	Aug.	25	49	71
IV	Nov.	23	63	86

There is no clear trend of seasonal changes in the estimated biomass and the totals are quite similar over the whole period. Roughly half derive from the relatively small Gulf of Nicoya.

The area with deep water fish, argentine, hairtails and others off Cape Sta. Helena was covered in surveys I and III with biomass estimates of abt. 50 000 tonnes and 15 000 tonnes respectively. These resources will be discussed under Nicaragua since they extend further along the edge of the shelf into that country.

A further rough separation of the biomasses of the broad groups of pelagic inshore fish can be made based on the distribution charts and the proportions in the catches. The results based on mean values from all four surveys are as follows:

PELAGIC I. This group is likely to have been underestimated because of incomplete coverage of the shallow inshore waters. A correction has been made based on an assumption of the same densities in these areas as those in the adjacent areas of occurrence. The data indicate an approximate equal abundance of engraulids and clupeids. The estimates of standing biomass for each of these stocks then will be 13 000 tonnes.

PELAGIC II. A splitting of this group in accordance with the catch compositions results in the following: lookdowns abt. 25 000 tonnes, jacks abt. 13 000 tonnes, barracudas and scombrids abt. 13 000 tonnes, others 4 000 tonnes.

3.5.2 Demersal resources

The data for the swept area analysis and catch composition of demersal fish comprise 19,41 and 41 trawl hauls from the first, third and fourth survey respectively. In addition four hauls were carried out in the 100-200 m bottom depth range during the second survey. These hauls have only been included when calculating annual means.

Demersal fish

The main demersal species in Costa Rica are snappers Lutjanus guttatus and L. peru and mojarra Diapterus peruvianus. Frequent in the catches, but at lower catch rates were butterfish Peprilus spp., toadfish Porichthys nautopaedium, flounder Cyclopsetta querna and lizardfish Synodus evermanni.

Catch composition

Table 3.5.3 shows the mean catch rates in kg/hour and the catch distribution by size classes for the main species of demersal fish.

Table 3.5.3 Costa Rica. Mean catch and catch distribution for the main species in a total of 113 hauls.
Species/ survey	Mean rate kg/hour	Number of hauls in catch groups						Rate of occurrence
		1-30kg	30-100kg	0.1-0.3t	0.3-1t	1-3t	>3t
Spotted rose snapper
	56	28	6	10			1	45/113
Peruvian mojarra
	26	12	9	9	2			32/113
Pacific red snapper
	6	15	3	2				20/113
Butterfish
	9	31	4	1				36/113
Flounder
	3	33	3					36/113
Lizardfish
	2	42	1					43/113

The species of commercial or potential commercial interest have been grouped by families and their catch rates are presented in Table 3.5.4.

Table 3.5.4 Costa Rica. Mean catch rates of total hauls by surveys for the main commercial groups. Shelf hauls 0-200m.
Family	Mean catch rates (kg/hour)
	Survey I	Survey II*	Survey III	Survey IV	Total
Butterfish	5		5	7	9
Snappers	17		180	27	77
Groupers	7		14	19	16
Grunts	2		11	5	7
Sharks	1		2	1	1

* Too few data. Only five hauls between 100 and 200m bottom depth.

Biomass estimates

Estimates of fish density by depth strata are given in the Data File, Annex 8. By multiplying these densities with the area of the shelf, given in Table 2.1, estimates of standing biomass are obtained by surveys and species or species groups. These estimates are presented in Table 3.5.5.

Table 3.5.5 Costa Rica. Estimates of biomass of demersal fish by commercial species, groups and surveys. 1 000 tonnes.
	Survey I	Survey II	Survey III	Survey IV	All surveys
Snappers	2.2		24	4	10
Seabasses	1		2	2.5	2.2
Grunts	.3		1.5	.7	.9
Butterfish	.9		1.5	1	1.2
Sharks	.3		.2	.1	.1
Other demersal fish	17		22	24	24
Total demersal fish	22		51	32	38

The snappers come out as a dominating demersal group during all surveys. The high biomass of snappers calculated on the third survey is due to an extraordinary high catch of spotted rose snapper, 3300 kg/h at st. 625. This sample might not be fully representative for a true catch distribution, in which case the estimated biomass would be too high. More hauls will be needed to improve the precision of the estimate.

The proportion of “other demersal fish”, consisting mainly of various non commercial fish such as Diapterus peruvianus, is seen to be high.

Shrimp. Mean and highest catch rates are shown in Table 3.5.6. Only few hauls were made for the deep water nylon shrimp Heterocarpus vicarius as the slope was untrawlable over large parts except near the border with Nicaragua. Here a catch rate of abt. 500 kg/hour was obtained for this species. Catch rates for kolibri shrimp Solenocera agassizii at intermediate depths did not exceed 20 kg/hour. Chrystal shrimp Penaeus brevirostris appeared only sparingly, but no special night surveys were made for this species. Various shallow water shrimps appeared in the catches especially during survey IV in November. The survey results may provide data for by-catch studies of existing shrimp fisheries.

Table 3.5.6 Costa Rica. Catch rates in kg/hour by main groups or species. Mean rates, highest rates and rate of occurrence.
Species	Mean rate	Highest rates	Rate of occurrence
Crystal shrimp	4*	22, 19 16	18/34
Colibri shrimp	3#	22, 22 19, 15	21/58
Other penaeids	3&	25, 25 13, 13	21/50
Pacific seabob	4&	64, 60 32, 17	7/50
Nylon shrimp	63$	510,100 14, 3	5/10

* Mean of 34 hauls in the 50-100m bottom depth range.
# Mean of 58 hauls in the 50-300m bottom depth range.
& Mean of 50 hauls in the 0-50m bottom depth range.
$ Mean of 10 hauls beyond 200 m depth.

Table 3.5.7 Costa Rica. Catch rates of dart squid in the 50-150 m depth range by surveys. Mean rates, three highest rates and rate of occurrence. Kg/hour.
Survey		Mean rate	Highest rates	Rate of occurrence
I	Febr.	36	75, 55, 38	5/11
II	May	7	12, 5, 3	3/4
III	Aug.	9	39, 18, 9	13/13
IV	Nov.	19	120, 54, 7	11/12

The estimates of biomass from the swept area calculations range from 700 to 1 200 tonnes. Because of incomplete coverage of the relevant depth range during the first part of the year this represents a gross underestimate of the true squid stock biomass.

3.5.3 Overview of survey results and estimates of standing biomass of the resources

The following groups of resources were identified and will be discussed:

Small pelagic fish was found in a few dense areas in all surveys in the Gulf of Nicoya and near its entrance, but often also eastwards towards Bahia de Coronado. The species in this assemblage consisted, as in Panama, of engraulids, clupeids, various carangids and sierra and barracuda, but relative proportions were different. Yellowfin herring dominated the clupeids. Lookdowns were the most common carangids and other large sized carangids and the predators sierra and barracuda were more abundant than further east. In Golfo Dulce fish was only recorded in the surface and near the entrance and this is probably related to the low oxygen content of the deeper water here. Significant concentrations of fish were not found in the Gulf of Culebra, but a deep water assemblage with hairtails, argentine and various sea basses was located in the offshore parts of the shelf off Cape Sta. Helena in the border area with Nicaragua. Catch rates particularly of barracuda and sierra were highest in the August survey.

Demersal fish had the highest abundance in the shallow range 0-50 m. The commercial fish in the catches was often large-sized. Snappers dominated among the commercial species. Good catches of this group were obtained off Bahia de Coronado and Gulf of Nicoya and inshore from Cabo Blanco towards Gulf of Culebra.

Shrimp. Deep water nylon shrimp was found with langostino in the border area with Nicaragua, but otherwise large parts of the slope were steep and untrawlable preventing further tests for these species. Smaller catches of crystal and kolibri shrimps were made and shallow water penaeids appeared in smaller amounts in the November survey.

Squid. Dart squid was relatively common in the appropriate depth range, 50-150 m. Survey data are incomplete but this may be an interesting species. The highest availability appeared to be off Bahia de Coronado and along the coast from Cabo Blanco to Gulf of Culebra.

3.5.4 Comments to the findings

The total Costa Rican marine fish landings in 1986 was 13000 tonnes and of this 1000 tonnes was small pelagics and about 4500 tonnes various demersals, scombrids and sharks. As a result of administrative problems there was an incomplete inshore coverage of Costa Rican waters especially in surveys I and II and some of the important demersal resources such as sciaenids and ariids are not included and others such as groupers seems to have been underestimated. Snappers seem better covered and both the distribution and the biomasse estimate may describe the stock. There is no fishing for carangids except as a by-catch in the shrimp fisheries and there seems to be an unused potential for these as well as barracudas and sierras. There is, however, need for further assessments and for verification of some of the estimates.

3.6 NICARAGUA

3.6.1 Small pelagic fish
3.6.2 Demersal resources
3.6.3 Overview of survey results and estimates of standing biomass of the resources
3.6.4 Comments to the findings

From Nicaragua onwards the coast and the shelf changes character with a straighter coastline, a wider even shelf and a slope from abt. 200 to 500 m or more which over large parts is smooth and fishable with trawl. Both available information and observations attained during the survey indicated that the areas of greatest interest would be the inshore regions and the part near the edge of the shelf and the slope itself down to about 400 m of depth. As described in Chapter 2.1. above prevailing offshore winds off the southeast coast during part of the year causes seasonal upwelling which no doubt contributes significantly to the productivity of the area.

The distribution of fish and crustaceans on the shelf from the northwest Costa Rica to the Gulf of Tehuantepec in Mexico can be described in a somewhat simplified way by reference to inshore and offshore faunas. The inshore fauna or assemblage of fish and crustaceans is found along the coast out to a depth of 60-70 m and consists of small pelagics, anchovies, clupeids mainly thread herring, carangids such as bumper, lookdowns and jacks, sierra, barracuda, demersal fish predominantly snappers and shallow water shrimps and lobster. The offshore assemblage is found near the edge of the shelf and over the slope. An important component in the food chain of this community is the mesopelagic fish, small (3-4 cm) mainly lanternfish with an often regular diurnal migration between 250-300 m during the day and the surface layer during the night. Concentrations of such mesopelagic fish were recorded over many parts of the slope and further offshore during the survey, but these observations are not included in the fish distribution maps. This type offish is, however, known to form food for squid and tunas and they represent no doubt an important food source for the various types of fish found on the edge and over the slope such as argentine, hairtails, seabasses and others. Langostino, Pleuroncodes planiceps and deep water shrimp, especially nylon shrimp Heterocarpus vicarius form further important components of this fauna near the edge and slope with mantis shrimp Squilla species at greater depth and giant squid Dosidiscus gigas pelagic in the waters from the slope offshore.

The intermediate shelf depths, from abt. 50 to 150 m held seldom any important quantities of fish, but in the upper part of this range grounds of crystal shrimp Penaeus brevirostris could be found and shelf squids, Loliolopsis and Lolliguncula species extend their depth range well below 100 m.

3.6.1 Small pelagic fish

Distribution

Figure 3.6.1 shows the distribution of pelagic fish in each of the surveys from the observations of the acoustic system. All surveys show similar features with a belt of recorded fish along the coast showing the inshore assemblage. In the February survey only scattered fish was found in this zone, otherwise aggregations were located, in some parts dense mostly between Corinto and San Juan del Sur. Recordings of fish offshore were especially high in the southeast in the February survey with spots of high density of hair-tails, argentines and seabasses near the shelf edge.

Figure 3.6.1 Nicaragua, Honduras and El Salvador. Fish distribution as recorded by the acoustic system, by surveys.(Survey 1)

Figure 3.6.1 Nicaragua, Honduras and El Salvador. Fish distribution as recorded by the acoustic system, by surveys. (Survey 2)

Figure 3.6.1 Nicaragua, Honduras and El Salvador. Fish distribution as recorded by the acoustic system, by surveys. (Survey 3)

Figure 3.6.1 Nicaragua, Honduras and El Salvador. Fish distribution as recorded by the acoustic system, by surveys. (Survey 4)

Catch composition

Additional information on the composition and distribution of the pelagic fish is contained in the results of the fishing experiments. It must be noted, however, that most of the fishing with bottom trawl formed part of the programme for the swept area biomass estimation of demersal fish and for this purpose the trawl stations are positioned more or less randomly and with no intention of obtaining high catch rates. Pelagic types of fish often formed substantial parts of the catches in these hauls and otherwise fishing for identification and sampling of pelagic types of fish was made both with demersal and mid water trawls. These data can add to our picture of the general occurrence and composition of the various groups and species, but they must be interpreted with caution. The catchability of these gears are often highly species and size selective, large sized schooling clupeids such as thread herrings have for instance a very low catchability while anchovy, smaller carangids such as bumper and scads and more solitary species such as sierra and barracudas are more easily caught both at the bottom and in mid water.

Complete catch records and various types of processed outputs giving catches by groups, species and surveys are available in the Data File to this report. Here we will only show some brief extracts of the catch data.

Table 3.6.1 shows the mean catch rates in kg/hour for the main groups/species of pelagic fish in the inshore assemblage for each of the four surveys in Nicaragua together with the three highest catch rates obtained and the rate of occurrence measured as the ratio of hauls with a catch of the group to the total number of hauls.

Table 3.6.1 Nicaragua. Inshore. Catch rates in kg/hour by main groups of pelagic fish by surveys. Mean rate, three highest rates and rate of occurrence.
Survey			Mean rate	Highest rates	Rate of occurrence
	ENGRAULIDS
I		Febr.	15	93, 4, 2	7/20
II		May	93	191, 176, 101	20/28
III		Aug.-Sept.	58	159, 140, 136	17/43
IV		Nov.	45	133, 126, 93	16/32
	CLUPEIDS
I		Febr.	112	407, 29, 6	4/20
II		May	13	45, 38, 18	15/28
III		Aug.- Sept.	58	306, 136, 92	16/43
IV		Nov.	33	122, 114, 50	16/32
	CARANGIDS
I		Febr.	220	1813, 169, 130	11/20
II		May	37	209, 135, 97	21/28
III		Aug.-Sept.	81	208, 170, 168	22/43
IV		Nov.	61	221, 207, 191	19/32
	SCOMBRIDS
I		Febr.	19	72, 27, 20	8/20
II		May	8	20, 10, 5	6/28
III		Aug.-Sept.	19	57, 46, 29	14/43
IV		Nov.	11	24, 6, 2	3/32
	BARRACUDA
I		Febr.	5	10, 8, 2	4/20
II		May	34	136, 87, 64	14/28
III		Aug.-Sept.	73	485, 117, 91	16/43
IV		Nov.	23	96, 42, 32	11/32

For all groups the combined catch rates and rate of occurrence were low in the February survey except perhaps for the carangids where a single unusually high catch of bumper raised the mean rate. Several of the groups, clupeids, carangids and scombrids were also poorly represented in the catches in the May survey. The August-September gave relatively high rates for all groups with some decline again in November.

The engraulids consisted mainly of Anchoa-species, some seven were identified with A. argentivittata silverstripe anchovy as the most abundant in May and August-September and A. nasus in November.

The most important forms among the clupeids were threadfin herring Opisthonema libertate and various species of longfin herrings of the genera Opisthopterus and Neoopisthopterus. The few larger catches were threadfin.

Catch rates for these pelagic schooling fish were low, but one should recall that the trawl is an unsuitable gear for these types of fish.

The carangid catches included a number of forms. In the August-September and November surveys where this group was most abundant lookdowns, almost exclusively Selene peruvianus dominated with abt. 60%, followed by bumper abt. 25% and jacks of the genera Caranx, Carangoides, Hemicaranx and Oligoplites with abt. 15%. Sierras were relatively scarce throughout, but barracuda were common especially in August.

Table 3.6.2 shows the catch rates and occurrence of hairtails Trichiurus nitens, argentine Argentina aliceae and seabasses, Diplectrum and Hemanthias species in hauls at depths exceeding 150 m in each of the surveys. The distribution of these fishes, especially the hairtail and the seabasses was spotty and the coverage both by depth and by area is probably not sufficiently similar to allow meaningful analyses between the surveys. Some catch rates were very high especially in the depth range 150-200 m and indicate the existence of a significant biomass in this offshore area especially along the edge of the shelf off San Juan del Sur.

Table 3.6.2 Nicaragua. Offshore. Catch rates in kg/hour by main groups of pelagic fish by surveys. Mean rate, three highest rates and rate of occurrence.
Survey			Mean rate	Highest rates	Rate of occurrence
	HAIRTAILS
I		Febr.	673	2990, 800, 190	5/16
II		May	318	2570, 700, 220	12/13
III		Aug.-Sept.	71	860, 230, 34	18/30
IV		Nov.	55	96, 84, 69	5/16
	SILVER SMELT
I		Febr.	10880	80000,4220,1100	8/16
II		May	474	1220, 760, 530	6/13
III		Aug.- Sept.	447	3200,2950, 760	20/30
IV		Nov.	443	1800, 660, 170	6/16
	SEA BASSES
I		Febr.	1770	15900,2900, 260	11/16
II		May	311	2670, 360, 200	11/13
III		Aug.- Sept.	1130	20000, 520, 310	19/30
IV		Nov.	43	100, 90, 60	9/16

Biomass estimates

Table 3.6.3 shows the estimates of standing biomass of the inshore assemblage of pelagic fish from the acoustic system by main groups: PELAGIC I corresponding to engraulids and clupeids and PELAGIC II to carangids, scombrids and barracudas.

Table 3.6.3 Nicaragua. Estimates of standing biomass of pelagic fish by surveys and groups. Inshore waters. 1 000 tonnes.
Survey		PELAGIC I	PELAGIC II	TOTAL
I	Febr.	7	20	27
II	May	27	1	28
III	Aug-Sept.	52	31	83
IV	Nov.	33	28	61

There is a considerable variation between surveys both in the totals and in the proportions between the groups. The high levels in August are also reflected in the catch rates as is evident from table 3.6.1. The shallow inshore areas not covered by the survey are relatively small and migrations to and from these do not seem a likely explanation for the variations. When studying the distribution maps for the pelagic fish in this area including Gulf of Fonseca and El Salvador the continuity of the inshore resources along the whole coast is clearly evident and it does not seem unlikely that shifts in their distribution could take place through movements of the stocks or part of them. The variations of the estimates for the whole area is also considerably smaller than that for Nicaragua alone. This would mean that such migrating stocks would represent resources shared between the countries. For the short lived species such as the anchovies there is probably also an annual production cycle which causes true fluctuations in the biomass. For the purposes of assessment of stock biomass it is proposed to use the mean of the estimates from surveys III and IV. A rough separation of the biomasses of the broad groups of pelagic inshore fish made based on the basis of the distribution charts and the proportions in the catches will then give the following results:

PELAGIC I. With adjustment for uncovered inshore areas the standing biomass for this group is estimated to 42 000 tonnes. Rough assessments of standing biomass give 22 000 tonnes for the engraulids and 20 000 tonnes for the clupeids.

PELAGIC II. When separated in accordance with the representation in the catches the total of 30 000 tonnes will include: lookdowns 11 000 tonnes, bumper 5 000 tonnes, jacks 3 000 tonnes, sierra and barracuda 11 000 tonnes. Especially for the last group in which the barracuda dominated the estimate must be considered as a minimum level for the stock biomass.

Argentine	75 000 tonnes
Hairtails	35000 tonnes
Seabasses	70000 tonnes
Total	180000 tonnes

Table 3.6.4 Nicaragua offshore shelf area including border area with Costa Rica. Estimated biomass by surveys. 1 000 tonnes.
Survey		Mainly hairtails	Mainly silver smelt	TOTAL
I	Febr.	57	24	81
II	May		2	2
III	Aug-Sept	19	13	32
IV	Nov.		5	5

The data include some hauls with very high catch rates and the precision of the estimates is probably low. One extreme catch of 80 tonnes/hour of argentine was, however, excluded from this analysis.

The hairtails and the argentines were found off the bottom also during the day and there may thus be a negative bias also in the swept area estimates. It is proposed, however, to accept 180 000 tonnes as a preliminary estimate of stock biomass for this offshore fish.

3.6.2 Demersal resources

The data for the analysis of the demersal resources in Nicaragua comprise 28,35,55 and 30 trawl hauls from the respective coverages. Below, only the highlights from the analysis with the main species or species groups are commented upon in the text The complete results from the analysis are included in the Data File. The complete tables in the Annex should be treated as work tables and estimates of density on the species level or by depth strata in these tables should be interpreted with respect to the number of hauls forming the base of the analysis.

The demersal fish fauna of the Pacific coast of Nicaragua can reasonably be grouped by four habitats by depth zones:

1) the nearshore habitat from the shore to about 50 m bottom depth,
2) the intermediate zone from 50 to 100 m,
3) the offshore habitat, from abt. 100 m to the shelf edge at about 200 m and
4) the slope habitat, from the shelf edge and unto about 300 m bottom depth.

The main demersal species in the nearshore waters 0-50 m are mojarra Diapterus peruvianus, spotted rose snapper Lutjanus guttatus, panama grunt Pomadasys panamensis and threadfin Polydactylus approximans. The intermediate zone 50-100 m is dominated by sea robin Prionotus ruscarius, butterfish Peprilus spp., croaker Cynoscion stolzmanni and lizardfish Synodus evermanni. The offshore region 100-200 m is characterized by argentine, rose threadfin bass Hemanthias signifer, searobin Prionotus spp., butterfish, cagua seabass Diplectrum macropoma and scorpionfish Scorpaena spp. The deeper waters 200-300 m hold some hake Merluccius angustimanus in addition to crystal shrimp and langostino.

Catch composition

Table 3.6.5 shows the mean catch rates in kg/hour and the catch distribution by size classes for the main species of demersal fish. The argentine and seabasses which form part of the offshore fish assemblage have already been discussed above.

Table 3.6.5 Nicaragua. Demersal fish. Mean catch rates and catch distributions by size classes and depth strata.
Depth/ species	Mean rate kg/hour	Number of hauls in catch groups									Rate of occurrence
		1-30kg	30-100kg	0.1-0.3t		0.3-1t		1-3t		>3t
0-50 M
Mojarra (Diapterus peruvianus)
	47	9	8	12		1					30/52
Spotted rose snapper (Lutjanus guttatus)
	43	14	9	1		1		1			26/52
Panama grunt (Pomadasys panamensis)
	16	29	7	2							38/52
Threadfin (Polydactylus approximans)
	7	22	8		2						32/52
50-100 M
Searobin (Prionotus ruscarius)
	107
Croaker (Cynoscion stolzmanni)
	60	6	2		2		0		1		11/23
Lizardfish (Synodus evermanni)
	16	10	6		2						18/23
100-200 M
Searobin (Prionotus ruscarius, P. quiescens)
	220										/40
Butterfish (Prepilus snyderi, P. medius)
	165	83	4		5		2
Hake (Merluccius angustimanus)
	53	3	1						1		5/40
Scorpion fish (Scorpaena sp.)
	36										/40
200-300 M
Hake (Merluccius angustimanus)
	134										/8

The 20-100 m depth range holds most of the fish of assumed commercial potential except the mostly deeper living butterfish and small seabasses. The average catch rates of all hauls in this depth range are shown by main commercial groups and surveys in Table 3.6.6. There is some variation between surveys but a tendency for a composition in the order snappers, grunts, sharks and groupers with a total mean catch of 86 kg/hour. A reminder that the surveys trawl programme does not simulate a commercial fishery is appropriate.

Table 3.6.6 Nicaragua. Mean catch rates of hauls in the 0-100m depth range by main commercial groups for each survey.
Family	Mean catch rates (kg/hour)
	Survey I	Survey II	Survey III	Survey IV	Total
Snappers	153	23	43	12	44
Groupers	5	8	6	3	5
Grunts	21	12	22	43	22
Sharks	60	10	12	1	15

Biomass estimates