CHAPTER 1. INTRODUCTION

1.1 OVERVIEW OF THE FISHERIES AND PREVIOUS RESEARCH IN THE REGION
1.2 PROGRAMME OBJECTIVES
1.3 METHODS OF INVESTIGATION, INSTRUMENTS AND EQUIPMENT
1.4 EFFORT OF INVESTIGATION
1.5 FISH TAXONOMY

1.1 OVERVIEW OF THE FISHERIES AND PREVIOUS RESEARCH IN THE REGION

As a preparatory activity for the programme a survey was made of available data and literature on the fisheries and resources of the region. This took the form of a document prepared under contract by Mr. Robin Mahon, Bellairs Research Institute, St. James, Barbados entitled “An overview of fisheries, fishery resource assessment and surveys of the North Coast of South America - Suriname to Colombia” (Mahon, 1987). This document provided a basis for the discussions at the planning meeting in Port of Spain particularly as regards the history of previous survey efforts in various parts of the region.

1.2 PROGRAMME OBJECTIVES

Representatives of the coastal countries of the region to be surveyed, and from IMR, FAO and ORSTOM, attended the meeting in Port of Spain in January 1988 and discussed and agreed on the various aspects of the programme. The agenda of this planning meeting included:

1. Presentation of the R/V “DR. FRIDTJOF NANSEN” as a research tool.

2. Discussion of main programme objectives introduced by the participants of the region.

3. State of fish taxonomy in the region.

4. Review of fisheries jurisdiction and fisheries agreements in the area.

5. Formulation of programme.

Describe the composition, distribution and abundance of the main components of the resources of small pelagic and demersal fish and crustacea on the shelf and slope for studies of the state and the potentials of the stocks.

Collect biological samples of the most important species for studies of growth, maturity etc.

Conduct taxonomic studies for the purpose of preparing a regional species guide.

Conduct oceanographic investigations and obtain satellite imagery for studies of the oceanographical regimes and their ecological characteristics.

Prepare charts based on echo sounder observations of bottom character.

Provide data of catch rates for specific selected gears and areas.

The acoustic coverage should be adapted to the distribution of the target resources for these investigations so that the highest survey intensities are in areas of high fish densities. This will be done by amendment of the basic survey grid on a current basis during the survey. Trawling with mid water and bottom gear for identification and sampling, form an integral part of the acoustic survey work. In areas where snappers occur in mid water over hard bottom, sampling with hand lines will be tried.

The acoustic system is directed towards the small pelagic fish and will only cover the part of the demersal fish found in mid water and non of the crustacean resources, although samples for composition, size etc. will be provided by the accompanying bottom trawl catches. In order to obtain further data on the demersal fish, a programme of swept area estimation will be carried out with prelocated trawl stations. When targeted on demersal fish these hauls must be made in day time.

Trawling for red spotted shrimp should be nocturnal while pink and brown shrimp can apparently be caught both day and night. The experimental shrimp fishing can not be expected to be on a scale which will allow estimates of standing stock, but results will provide biological sampling and some distributional characteristics.

The Japanese survey off Suriname and other surveys further west have demonstrated the presence of various species of deep water shrimp in the slope at 200-900 m. In this survey some test hauls can be made to provide information on catch rates and species composition of these resources and for biological sampling.

SURINAME. For the inshore and shrimp surveys special attention should be given to the areas off the mouths of the large rivers: Maroni, Suriname, Coppename and Corentyn, and for the mid and offshore surveys, to the central snapper ground between 30 and 40 m and the snapper ground near the edge at about 80 to 100 m.

GUYANA. Special efforts should be made to provide data for studies of the by-catch of the existing shrimp fisheries through bottom trawling on the shrimp grounds. The main season for the offshore shrimping starts in April-May. Also work on deep water shrimp is desirable although a 1980 survey with the DDR stem trawler “ORKNEY” found little suitable trawl bottom beyond 100 m depth. There is need for information on the stocks of fin fish exploited by the artisan small scale fishery.

VENEZUELA. In the Orinoco Delta emphasis should be given to the collection of observations on the shrimps and the by-catch in the shrimp fisheries, the last with special reference to the sciaenid, lutjanid and scombrid species.

The specific objectives for TRINIDAD and TOBAGO for the first survey were stated as follows: The area to be covered should be the east coast between 10°N and 11° 30'N and out to 500 m depth. In addition to data from the acoustic and fishing systems for description of composition, distribution and abundance and biological sampling, bottom long lines should be fished in selected areas to establish catch rates for snappers and sharks. A programme for collection of water samples from various parts of the area for later analysis of hydrocarbons and heavy metals was to be included.

For the following surveys the objectives varied somewhat. The shelf off the north coast was included in the 2nd and 4th surveys, and for all surveys the east coast coverage was repeated without long line trials, but with deep water trawling to 800 m and intensive trawl and acoustic coverages were made in the Joint Fishing Area with Venezuela.

For the eastern part of VENEZUELA, Oriente, the area of main interest starts from abt. 63°W with the shelf of the Testigos Archipelago onwards. The shelf further to the east may thus be covered less intensively. The separate small shelf area east of the Blanquilla Island should be included. For the central and western central areas work on the slope should be included, possibly with sampling down to 400 m or more and with biological sampling of most of the groups mentioned for the Oriente. For the western area a special detailed survey should be made of the Gulf of Venezuela. Of special interest for the purpose of biological sampling are penaeid shrimps, snappers, catfish, grunts, groupers, scombrids, sharks and cephalopodes. Hydrographic profiles should be worked outside the Gulf of Paria, the Cariaco Trench and the Paraguana Peninsula.

Some minor amendments were made in the objectives of the later surveys with shifts in the positions of hydrographic profiles, increased priority in the coverage of squid grounds and testing of the deeper parts of the slope for deep water shrimp, and reduced priority to be given to the shelf inside the Cariaco Trench west of Puerto de la Cruz.

For COLOMBIA, the following applies: The more recent exploratory surveys include that organized by the FAO Fishery Development Project, 1969-71 with the R/V “CHOCO” and the programme jointly with Japanese Agency for International Cooperation (JICA) with “CARIBBEAN STAR II” in 1980/81. The first was focused on the demersal fish and thread herring, the second on shrimp on the slope (250-800 m) and snappers at 100-200 m depth. Taking account of the results of these programmes the more specific objectives of the present surveys should include:

i) Identify the areas of distribution and concentration of the thread herring Opisthonema oglinum in the Guajira Peninsula.

ii) Identify the areas of distribution and concentration of the squids Lolligoncula brevis southwest of Cartagena and Loligo plei east of Sta. Marta.

iii) Confirm the distributions and concentrations of the deep water shrimps Hymenopenaeus robustus and Plesiopenaeus edwardsianus.

iv) Confirm the areas of distribution and abundance of the sardine Sardinella aurita in the existing upwelling zones off the Guajira Peninsula.

v) Confirm the area of abundance of the family Lutjanidae in the south-east zone with hand lines, vertical lines beyond 100 m.

vi) Exploratory fishing in the insular zone of San Andres (hard-bottom coralline fish).

Technical problems with the vessel unfortunately resulted in curtailing of the full planned effort in several of the surveys in Colombia, but the high priority area in the east was covered in all four cruises.

1.3 METHODS OF INVESTIGATION, INSTRUMENTS AND EQUIPMENT

The pelagic schooling fish was investigated using acoustic integration technique combined with fishing with bottom and mid water trawls for identification and sampling. Fish near the surface and very close to the bottom are not properly observed with this system. Horizontal ranging sonar was used to observe surface schooling fish, but such observations are not easily quantifiable in terms of measure of biomass.

The reliability of acoustic techniques in providing estimates of biomass is under continuous review by the scientific community. There is little direct information available on the acoustic target strength of fish species from low latitudes. For the pelagic fish biomass estimates are based on an assumption of a target strength similar to that of the European herring. Some observations on the dimensions and volumes of the swim bladder of the main species of the region, indicate that this assumption has not grossly biased the results. Another limitation is found in the incomplete coverage of inshore waters by the survey, since the parts of the shelf shallower than about 10 fathoms could not be navigated by the vessel.

The overall effects of these various limitations are thought to lead to an underestimation of the biomass.

The identification of the targets recorded by the acoustic integration system represents an important problem. The basis for this step is the composition of the catches in hauls with bottom and mid water trawls together with an evaluation of the characteristics of the echo traces. Because the catchability offish is highly species and size dependent, the catch data must be used with considerable reservations and in areas where many species occur in mixture, identification can only be made by relatively broad groups. Some species occur, however, in distributional patches or in larger continuous aggregations and this facilitates the identification. The integrator values were allocated to the following groups:

Clupeids and anchovies
Carangids, scombrids, barracudas etc.
Demersal fish in mid water.

The swept area trawl survey method carries with it a special problem of estimation viz. which value to assign to the catchability quotient, q. We have used 1 which implies that all fish in the path of the gear are caught and contained in the catch. It seems, however, likely that part of the fish escape through the meshes and over or under the trawl and that this may exceed the herding effect of the sweep wires. The assumption q = 1 thus probably results in underestimates of biomass.

The incomplete coverage of inshore waters caused by the vessel's operational limitation of 10 fathoms also affects the results of the study of the demersal fish with bottom trawl. The inshore faunas of bottom fish may thus be incompletely sampled especially in estuarin regions with possible underrepresentation of inshore forms.

The results of the fishing experiments also provides information on the composition and distribution of the resources both pelagic and demersal and to a limited extent the catch rates that can be expected. 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 some times formed substantial parts of the catches in these hauls. These data must, however, be interpreted with caution. The catchability of these gears are often highly species and size selective, large sized schooling clupeids, such as sardinella has for instance a very low catchability, while anchovy, smaller carangids, such as bumper and scads and more solitary species, such as Spanish mackerel and barracudas are more easily caught both at the bottom and in mid water although the bottom trawl is generally not an adequate gear for such pelagic fish.

The available effort for the swept area trawl programme in these surveys is not considered sufficient for stock studies of the many resources of short lived penaeid shrimps in the area. By pooling the data from all four surveys one could at best obtain an estimate of the mean standing biomass of species which would be of little interest. The shrimp data may, however, provide evidence of annual trends in shrimp abundance and give size compositions. In addition amounts and composition of fish by-catch may be extracted. Some of the data on deep water shrimp may give indications of likely catch rates.

It is important to note that with the survey methods used and the survey efforts concentrated inside the shelf no information could be obtained on the large pelagic fish, tunas, billfishes, large sharks etc. which represent important resources in parts of the area.

For description of the acoustic instruments used and their calibrations, reference is made to Annex 1.

A brief description of the trawl gears used is also presented in this Annex.

1.4 EFFORT OF INVESTIGATION

The survey programme covered a period of one year from January to December 1988. The timing and number of days spent working in the waters of each country with distance steamed and number of fishing stations worked are set out for each survey in Table 1.2.1. The survey generally covered the shelf from about 10 fathoms of depth to the shelf edge at about 200 m with some work also on the slope when doing hydrographic profiles or testing for deep sea shrimp. The density of the course tracks is for each survey lag indicated as the ratio between the distance steamed and units of 100 nm² of shelf covered. The density was adjusted to resource distribution, in general with higher densities in areas of high and variable concentrations of fish. An adjustment was also made relating to the specific objectives for certain areas.

The total field effort of the survey comprised about 155 days of active research work with some 27 000 nm steaming and 1 200 trawl stations worked.

Table 1.2.1 Details of investigational effort in the four surveys.

SURVEY	DAYS	DATES	DISTANCE (nm) TRAVELLED IN SURVEY AREA	SURVEY INTENSITY nm/100 nm2*	NUMBER OF FISHING STATIONS	NUMBER OF HYDROGR. STATION
I
SURINAME	6.5	22-29/1	1300	7.8	44	7
GUYANA	5.5	30/1-4/2	950	6.1	40	8
ORINOCO AND JOINT FI. AR	2.5	4-6/2	460	6.6	20	6
TRINIDAD	5	9-13/2	1000	17.9	19	8
VENEZUELA
ORIENTE	9	15-23/2	1500	12.4	59	14
VENEZ. WEST	10	23/2-4/3	1500	12.7	79	8
COLOMBIA		4-11/3	1100	13.5	38	12
II
SURINAME	5	8/5-12/5	1000	6.1	40	7
GUYANA	5	12-18/5	700	4.5	40	8
ORINOCO	3	18-21/5	400	7.0	28	6
TRINIDAD	4	23-26/5	700	12.5	25	12
JOINT FI. AR	2	26-28/5	150	12.0	22
VENEZUELA
ORIENTE		30/5-5/6	1100	9.1	50	14
VENEZ. WEST	16	5/6-14/6	1400	11.8	54	19
COLOMBIA	5	14-21/6	900	11.0	40	12
III
SURINAME	5	11-15/8	930	5.6	27	7
GUYANA	5	15-19/8	700	4.5	42	6
ORINOCO	2.5	19-22/8	470	8.2	18	5
TRINIDAD	3	23-26/8	700	12.5	11	9
JOINT. FI. AR	2	26-27/8	150	12.0	27
VENEZUELA
ORIENTE	8	29/8-7/9	1700	14.1	68	12
VENEZ. WEST	8	8-15/9	1000	8.4	57	13
COLOMBIA	8	15-23/9	1100	13.5	57	9
IV
SURINAME	5	29/10-4/11	1000	6.1	40	8
GUYANA	5	4-12/11	900	5.8	45	8
ORINOCO	2.5	12-12/11	500	8.8	15	6
TRINIDAD	4	13-17/11	800	14.3	32	12
JOINT FI. AR	1	18-20/11	300	24.0	26	10
VENEZUELA						6
ORIENTE	8	21-28/11	1260	10.5	53	12
VENEZ. WEST	9	28/11-7/12	1270	10.7	54	11
COLOMBIA		7-11/12	500	6.1	30	14

* 0-200 m.

Suriname:

Yolanda Echteld, J. A. Emanuels, Chanderalth Gajadin, Heidi Jessurun, Rene Lieveld.

Guyana:

George Bailey, Cole Compton, Maurice Phillips, T. Phillips.

Venezuela:

Ayuramy Alcalá, Douglas Altuve, Marco Tulio Badaracco, Mauricio Campo, Roberto Cipriani, Orlando Ferrer, Luisa Franco, Leo Walter González, Ramon Guzmán, Luis Marcano, Bladimir Rodríguez, Wilmer Rojas, Jesus Segovia, Efigenio Velásquez, Diana Zaera.

Trinidad & Tobago:

Sammy Alleyre, Alan Aruato, Erol Caesar, Ronald Chan-A-Shing, Boris Fabres, Leo Heilemann, Sherry Heilemann, Christine Henry, Wayne Jittan, Ahmad Khan, Sita Kuruvilla, Anthony McDowell, Gerald Mitchell, Anthony Nakhid, David Ramjohn, June Sammy, Maxwell Sturm.

Colombia:

Santiago Anboleda, Carlos Barreto, Manuel Barrios, Luis Escobar, Jorge Gallo, Carlos Guerrero, Jorge Infante.

FAO:

Luis Villegas, Alvaro Abella.

IMR:

O. Alvheim, G. Bianchi, M. Dahl, O. Hagstrøm, J. Hamre, T. Haugland, J. Kolding, E. Molvær, T. Strømme, I. Svellingen, G. Sætersdal, H. Ullebust, H. Vorren, D. Zaera.

1.5 FISH TAXONOMY

A total of about 1100 species were identified in the course of the survey programme, including bony fishes, sharks and rays, shrimps, lobsters and cephalopods, with the help of the FAO Species Identification Sheets for Fishery Purposes, Fishing Area 31, vols 1-6, and the FAO World Catalogues, produced for several major groups (clupeoids, scombrids, snappers, sharks and rays and cephalopods).

With the assistance from this programme, FAO has undertaken the preparation of a Species Identification Guide for Trinidad and the Guyanas. For this purpose, a large number of specimens was collected and sent to specialized taxonomists throughout the world. Also, more than 200 photographs were taken, including fishes, cephalopods and invertebrates. The guide is expected to be completed by the end of 1990.

Contacts have been established with local fishery institutions to collaborate in compiling further data on occurrence, habitat, fisheries and vernacular names.