1.1.1. General description of the species
The Giant freshwater prawn (or Malaysian prawn) Macrobrachium rosenbergii is well-known in aquaculture from the seventies with the control of the whole life cycle of this species. Its original basin is South-East Asia but it quickly showed such qualities of adaptation and reproduction reliability that it has expanded worldwide along the tropical belt. The larval phase lasts 30 to 40 days in brackishwater (estuarine or mangrove areas in the wild) and the grow-out phase occurs in fresh water (marketable adults can be harvested at 40–50 g each from the seventh month after seeding in ponds). More than 60 different species of the genus Macrobrachium have been recorded and described, especially M. carcinus and M. acanthurus, common all over the Caribbean islands. However the most suitable species in terms of larval survival, growth speed and crowd behaviour in pond, remains M. rosenbergii.
Hatchery mass production technics are now fully reliable and different systems can be used for grow-out according to the local constraints : seasonality (low temperature in wintertime), water availability, market standards, etc. In that region, the production yields range between 1 and 3 tons of prawns/year and per ha of pond.
1.1.2. Main requirements
The hatchery phase requires good availability of unpolluted marine water and freshwater to ensure a top level quality for the rearing water. Whatsoever, the hatchery is designed and equipped to obtain a permanent and optimum control of the brackish water even in case of silt or high bacteria density in the intake waters. The recirculated system allows to make easier this control and saves water supply. Electrical (medium voltage) energy must be available close to the hatchery site.
The hatchery site must be close to the sea with a relatively quiet area for pumping. A good quality freshwater must also be available with a well from the phreatic water table. Some broodstock ponds are necessary in the vicinity of the hatchery especially when a pilot-scale project is necessary (as in Grenada). This implies the need of a minimum of flat land close to the hatchery to facilitate broodstock manipulations in good conditions.
A good site for the grow-out phase requires :
Moderate slopes ( < 5 %) ;
Absence of rocks or big stones ;
Loam type soils, although sandy loam, clay and silt soils can also be used ;
Good availability of freshwater with suitable composition (see detailed analysis in Annex VI). The usual ratio for the flow rate is 10 liters per second for one hectare (10 000 m2) which is roughly 10 % water renewal per day for a 0,9 meter deep pond.
Agriculture, industrial and urban pollutions must be avoided. As a matter of fact, the “usual” pollution from agriculture treatments and scattered housing wastes appears to be easily tolerated by the prawns in ponds, according to what is observed in some islands of the area (Martinique, etc).
However, ponds below towns and mid-size factories must be forbidden.
The ponds can be located in many areas unless sufficient gravity water and some hundreds of square meters are available. The first prawn pond in Grenada (see section II, 3.1.) is a good example for this. The main large areas are located close to the seashore with gravity freshwater available. Usually there is no limitation concerning the type of soil in those areas. The major constraints are :
Flat land disposal ;
Year-round freshwater supply.
The ratio of 10 liters/second for one hectare indicates the maximum surface available for prawn aquaculture.
1.1.3. Technical potentialities
For the hatchery, an excellent site has been located close to telescope point either on the left bank of the Great River or on the right one with a bonus for this second due to a good wave protection through the natural coral reef. Other sites can be also preselected especially in the south east sheltered bays (see Annex 8).
About 90 ha in coastal areas and 10 ha in inland zones have been identified. Annex 7 details the most interesting areas and the limiting factors for each. Of course, more data especially on water flow in small southeastern rivers would be useful. The final available surface for each site has also to be considered as a minimum with a good safety margin. Most of these areas belong to the Government.
The experience of freshwater prawn development in the French West Indies teaches that some “major” farms (4–10 ha each) can find their place among plenty of small others. Especially if the total available area is limited as it is in Grenada (100 ha).
IDENTIFIED HATCHERY SITES (For freshwater prawns)
IDENTIFIED GROW-OUT SITES IN GRENADA
(For freshwater prawns)
1.1.4. Aimed market
The local equivalent for prawn is the “crayfish” (“cribiche” or “onassous” in creole) which reaches high prices (18–25 EC/pound according to the size of the animals) even when its presentation or appearance is poor. Some inquiries in restaurants, hotels and among private people indicate that a price of 15–18 EC/pound would be reliable for a preliminary economic analysis.
The market will be local for the first years of production, probably up to 50 tons. Later on, if new ponds still appear every year and if the technical level of farmer keeps rising as it happens in french overseas territories (200 pounds of increase every year per hectare and per year with a baseline at 1 T/ha/year) an export could eventually start (provided the local production cost be competitive on the international market) especially to US and Trinidad markets using existing facilities and lines for those destinations.
1.1.5. Potential interest for the country
The development of that activity is of high interest for the country as :
The process if fully controlled ;
It can immediately start on a commercial scale provided the proper technology and know-how be introduced in the country ;
Grow-out farms are financially accessible to both large and small private investors ;
The activity will be financially viable ;
With a production objective of 50 tons only (for local market), the directly created jobs in the grow-out farms could range between 70 and 90 (induced jobs not included) ;
The activity is a low energy consumer (water supplied into the ponds by gravity).
1.1.6. Preliminary financial analysis of a small grow-out farm
The financial characteristics (basis Oct. 1986) of one small grow-out farm (5 ponds of 2 000 m2) are detailed in Annex I (Annex I1 to I4). They can be summarized as follows :
Investment costs (capital costs) : 152 000 EC ;
Production yield : 2,7 tons/ha/year ;
Gross profit before tax (financial cost not included) in standard year :
40 000 EC/year if animals sold at 17 EC/pound
Production cost : about 10, 3 EC/pound (financial costs not included) for head-on fresh animals ;
Financial Internal Rate of Return :
1.2.1. Suitable species and description of the process
2 main products appear suitable for farming in Grenada. They are the tilapias and carps. The usual interest of these two species can be summarized as follows :
Fully reliable production process including both hatchery and grow-out phases ;
Production of good protein at a low cost (the usual semi-intensive grow-out technics do not require additional feed) as the animals feed on natural production in the ponds ;
The 2 species can be grown with a semi-intensive (1) of extensive (2) process in large earth ponds (from several hundreds of square meters to several hectares) while the tilapia can also be grown in intensive systems (floating cages in lakes or onshore concrete ponds) provided a dry pellet be available (about 15–20 % protein).
1.2.2. Suggested approach for Grenada
So far, in Grenada, people are not used to consume freshwater fishes even in the inland areas. It means that any development of freshwater fishes aquaculture should be associated with a strong effort for promoting the product. The worldwide experience shows that such promotion programs are always long and sometimes unsuccessful. Furthermore, as described in section II.2 the supply of fishes in Grenada could be easily increased with an improvement of the marine fisheries sector. Under these conditions, the consultants team suggests to limit the perspectives of development on the two lakes : Grand Etang and Lake Antoine.
On each one of the lakes, the following small projects could eventually be developed :
Restocking the lakes for extensive culture with various species of carps such as :
A restocking with adapted percentages of each species will allow an optimal utilization of the food chain inside of the lake.
This restocking should be associated with the introduction of a carnivorous species (various species such as Clarias spp.) and freshwater prawns.
The objective of that project would not be a mass production but mainly the production of big animals (carnivorous fishes and big freshwater prawns) for sportsfishing in a local touristic complex (restaurant, boats for fishing, traps, etc).
(1) Additional cheap feed such as rice bran, agricultural by-products is required to achieve production yields of 1–3 tons/ha/year.
(2) Production yield about 200–500 kg/ha/year without additional feed.
2.1.1. Suitable species and status of the art
The most promising species for cultivation in the caribbean region are the following :
Lutjanids : Ocyurus chrysurus, L. analis ;
Carangids : L. Griseus, Trachinotus falcatus and T. goodei ;
These species (except for Lates) are often caught (among many other species) in Grenada with beach seines and here too, they are highly appreciated by both the local consumers and the foreign tourists.
Unfortunately, so far, the culture process is not reliable even if promising and encouraging results have been achieved in various large research centers (mainly in Martinique, Miami, Tahiti and Hawaï). In the caribbean region, the following elements are still bottlenecks :
Source of juveniles :
It is difficult to find sufficient concentration of fingerlings in the wild ; thus the control of the mass production of juveniles in a hatchery is essential. Different laboratories are on the verge to obtain it.
Grow-out units :
The main research programs presently focus on intensive grow-out in floating cages in protected bays. Many shapes and materials can be observed : circular, square, polygonal, in wood, iron, fiberglass, etc. The most reliable and cheapest system appears to be the horizontal cylindro-conical cages used in the French Antillas. They can be quickly sunk (immerged) in case of hurricane. Their greatest advantage consists of the automatical destruction of the fouling with the regular rotation of the cage (the superior part is above the water level and the algae are sundried).
Some research efforts remain necessary on feed optimization (1) and definition of a correct diet. However, various parameters such as growth, densities, usual pathology are more and more known.
(1) Note : Lates calcarifer (non-indigeneous species) in commonly reared in floating cages in South East Asia. For that species and in the context of Far East, the utilization of trash fish as basic feed in common and financially viable.
2.1.2. Suggested approach for Grenada
The local demand and the possibility for export (Martinique, Trinidad, etc) of these high value fishes are undoubtedly important. In addition, Grenada shows many protected bays that are very favourable for aquaculture in floating cages ;
However, 2 points are disfavourable to this activity in Grenada, they are :
First point : A local investigation program would be necessary before reaching the level of commercial production. It's impossible and unrealistic to consider such programs in Grenada in the present situation (lack of skilled staff and facilities, etc).
Second point : A large amount of these fishes is now available in the wild. No doubt that an improvement of the fisheries sector will immediately increase the offer of those species on the market and aquaculture would not be financially competitive.
Under these conditions the consultants team does not suggest to promote the aquaculture of fin-fishes in the region. Priority should be given to the fisheries sector.
2.2.1. Suitable species and process description
As presently described in the sections II, 4.1. and III, 1.1.3. about 90 ha of flat lands have been identified in coastal areas. Such lands are suitable for both freshwater prawns and marine shrimps culture. Considering their physical characteristics (flat lands, easily drainable, soil with clay, vicinity of seawater) and the quality of the waters (marine water and freshwater) they are fully suitable for semi-intensive culture in brackish-water with earthmade ponds. This technic consists of stocking ponds with shrimp post-larvae (wild juveniles or P.L. produced in a hatchery) and feeding the animals for 6 months with an adapted dry pellet (25–30 % protein) until they reach the market size (20–25g/animal). About 10 % of the water volume is daily renewed. The expectable production yield ranges between 1,5 and 2 tons/ha/year.
Two species are currently produced with this technic in the Americas (Ecuador : about 35 000 tons in 1985, Panama, etc) ; they are Penaeus vannamei and P. stylirostris. Both of them are native of the pacific coast. However, the sexual maturation of breeders in captivity and the hatchery phase are now fully controlled at a commercial and industrial level. This makes now possible the introduction of these species on the atlantic coast (full control of the life cycle) and in Grenada. Alike for freshwater prawns various suitable sites for hatcheries have been identified in Grenada.
2.2.2. Suggested approach for Grenada
No doubt there are technical potentialities to produce marine shrimps in Grenada and the technic would not be the limiting factor. However, the consultants team does not advise to promote or develop the grow-out activity in Grenada for the following reasons :
Due to the too small size of the available lands (not more than few ha per site), it will not be possible to implement large industrial farms (one industrial farm in Ecuador frequently sizes more than 100–200 ha) in Grenada. Thus, the local production cost will not be competitive on the international market and it will not be possible to export the production ;
This activity is a high energy consumer (marine water must be pumped) and must not be developed in Grenada.
Only industrial hatchery projects could be developed in Grenada. The elements of justification for such projects are :
The technical suitability of various sites (mainly in terms of water quality) in Grenada for large and reliable industrial marine hatcheries ;
The cheap labour cost that will allow a low production cost of post-larvae, even if the local energy cost is high. In the present conditions, the production cost should range between 4 and 5 US $/1 000 P.L. for an industrial unit ;
The present demand of P.L. in Latin America is incredibly high (about 15 billion are required every year with 90 % for Ecuador only) as the existing hatcheries are far from fulfilling the requirements. Last year, P.L. prices increased up to 15 and sometimes 20 US $/1 000 P.L. Undoubtedly, hatcheries will make a large profit in the next-coming years provided they can produce on a reliable basis (many hatcheries in Latin America face pathological problems with virus infection).
2.3.1. Suitable species and status of the art
An initial assessment of the development potential of the Carriacou island by Crane and Rojas in January 1985 suggested commercial development of the natural oyster beds in Carriacou. Therefore the Organization of American States (O.A.S.) contracted with Glude Aquaculture Consultants, Inc. to conduct a prefeasibility study on such a development in Carriacou.
That last study showed that there are adequate populations of the mangrove oyster Crassostrea rhizophorae and the flat oyster Isognomon isognomon to provide spawning stocks (thus, a hatchery is not necessary). It is obvious that oysters grow and survive well in Tyrrel Bay but field tests at an experimental level are necessary to provide a basis for the selection of appropriate methods for a large production.
2.3.2. Suggested approach
Although grow-out of oysters can likely be carried out in Tyrrel Bay, the consultants team is doubtful on the interest of the operation. That position results from the following factors :
The local population (Carriacou and Grenada) is not used to consume these oysters and furthermore the international market of mangrove oysters is extremely small (local consumption in production areas) ;
It is not sure that the local species are the best ones for aquaculture : the japanese round oyster Crassostrea gigas when introduced in similar waters usually shows better growth performances (1).
The natural productivity of phytoplancton and microbenthos is limited in the region except for Tyrrel bay (mangrove area). Thus, the possibility to apply the results (even if good) to other areas is limited ;
A research program will be necessary ;
Under these conditions, the consultants team does not advise to carry out an investigation program on a product that shows so few possibility of development.
(1) Trials have now been performed in Cuba for 3 years to compare in cuban waters the growth performances between the japanese oyster and the local mangrove oyster (Crassostrea rhizophorae). The results have clearly demonstrated that the japanese oyster has a faster growth and a better ratio
2.4.1. General description of the process and main requirements
Various seaweeds are collected and used for food in the West Indies. Which ever species are used, they all form the main ingredient in the very popular seamoss drinks, porridge and puddings that are famous thoughout the english-speaking Caribbean. Most of the seaweed species used as seamoss are members of the genus Gracilaria and contain agar which is commonly used as a thickener. The commonly used species are G. crassissima, G. debilis, G. domingensis and GT. A Gracilaria. Up to now, all seamoss used in the West Indies is harvested from wild stocks. These stocks are now severely depleted as a result of overharvesting and of poor harvesting methods.
Under these conditions, the supply of seamoss by cultivation could be one solution. It justified the research program now under course for 6 years in St-Lucia where coastal communities began commercial seamoss culture in 1985 for the local market.
b) Process description
(Réf. : “A guide to seamoss cultivation with West Indies”, published by Caribbean Conservation Association in 1986).
Propagation methods : 2 methods can be used
Spore recruitment by collecting spores on artificial substrates such as ropes to wich they attach and then grow ;
Vegetative propogation using cuttings from mature plants as seed materials and attaching those to ropes for cultivation.
Source of seed material
For vegetative propogation, seed material for the first planting must be collected from wild populations. Thus, some management of the resource may be needed to ensure that the wild stocks are maintained.
Cultivation methods and production yields
Once the lines (ropes) are seeded they should be outplanted at the farm site by attaching them to stakes or rafts. The grow-out period usually lasts between 2 and 4 months, depending on many factors such as water conditions, quality of seeding and maintenance. At one farm in St-Lucia, GT. grown on rafts yields about 2 kg fresh weight per meter of line after 2 months (about 0,5 pound dry weight/yard of rope). G. domingensis and G. debilis should give similar yields after respectively 3 and 4 months.
At harvest, the plants (about 200–300 mm long) are cut about 50 mm from the rope, leaving the base still attached. The cut ends will soon produce new shoots for the next harvest. That can be repeated 3 or 4 times before a complete re-seeding of the lines.
Processing involves cleaning and rinsing of the plants before sundrying them. With that process water content decreases from 85–90 % to about 30 %. Final packaging usually uses plastic bags.
c) Technical requirements
A selected site for the implementation of a grow-out farm should fulfill most of be following parameters :
A firm substrate, such as seagrass beds, or sand ;
Moderate wave action ;
Good water exchange, especially if nearby river outflows carry freshwater and sediment into the area after rainfalls and reduce the salinity ;
A water depth of at least 1.0 m at low tide.
Nearby coral reefs, which have numerous herbivorous fish feeding on the algae, should be avoided.
2.4.2. Technical potentialities
Grenada and Carriacou show large potentialities for the development of seamoss culture. The main favourable areas are :
In Carriacou : the Tyrrel bay and eventually the watering bay (provided the waves be not too tough).
In Grenada : most of the large protected bays from Grand Bacolet Bay (East coast) to Hardy bay (south coast) appear suitable for seamoss culture. On the south west-coast Morne Rouge Bay should also be suitable. However, the bays with relatively large rivers should be avoided.
2.4.3. Aimed market
There is a local market where seamoss is being collected for use. The seamoss may be sold locally or, in some islands, to people who export it to Trinidad and Barbados, where the prices are the highest in the West Indies. In conclusion, there is a good and reliable market in the caribbean islands. As regards the north-american and european markets they are extremely uncertain (the industries need agar but as a raw material and at low cost).
2.4.4. Interest of seamoss culture for Grenada
The interest in Grenada of that form of aquaculture can be summarized in the following terms :
Local market and potential profitable market in the caribbean region ;
Activity well fitting in the present socio-economic structure of both Grenada and Carriacou : one part of the fishermen population could easily be shifted from fishing to seamoss culture as they are well used to the required manipulations (mainly handlings from boats or rafts) ;
No energy-consumer activity ;
Many suitable sites ;
Activity financially accessible to small investors;
However, local research programs and field tests are required before starting commercial projects.
During its visit to Carriacou, the consultants team could visit the “King crab” project, based in watering Bay. That project is, so far, financed by a private investor who faces financial difficulties to continue it. One will find in the present section a description of the present status of the project and a justification of its interest.
2.5.1. Description of the status of the art and main technical requirements
The Caribbean King crab Mithrax spinosissimus unhabits mostly deep coral reefs in the Caribbean and Bahamas. All along its life, from the newly hatched larvae to market size (about 2 kg) it feeds on algae.
b) Process description
Gravid females have been imported from Dominican Rep. and placed in hatchery boxes (wooden cages about 1 m3 floating in subsurface and covered with an adapted mesh about 0,5 mm). After hatching the females are removed while the larvae (1 mm in lenght) are kept in the initial hatchery box. It must be pointed out that the larval phase lasts 60 hours only from the zoea stage to the crab-like (megalops) settling on the chamber screens.
Grow-out to 100 days
Few hours after metamorphosis, the megalops are transferred to a juvenile crab grow-out cage. That cage is suspended in the water column beneath the water surface. As the animals are hervivorous, grids covered with algae are frequently added in the cage while the former are removed. After 100 days, the young crab bodies are 15 mm in diameter.
Final grow-out to market
After 100 days in a juvenile grow-out cage, the animals are removed and stocked in bigger cages with a larger mesh size. During that phase the animals are only fed with algae. The market size has not yet been achieved in Carriacou. However, the marine biologist in charge of the project expects the animals will reach 2 kg within about 18 months from hatching.
Production of algae
From the larval stage to the market size the animals appear to feed exclusively on algae diet. The algae are naturally produced outside of the rearing cages on a grid fixed by a PVC frame. The grids are remained floating on the surface of the sea (attached together on a floating longline) until they are covered with algae. Then the grids are placed in the rearing cages.
c) Technical requirements for grow-out site selection
Due to the utilization of floating cages and the required production of algae on a large scale, the requirement for site selection are similar to these for seamoss production, i.e. mainly :
Protected bays with a constant pure marine water and no risk of salinity decrease due to too large rivers ;
Limited waves ;
Not too close to coral reefs for avoiding the presence of herbivorous fishes.
d) Judgement on the present status of the art
The project is still at a Research-Development level and it is not advisable to start now on a commercial basis because it is too early. The propagation and grow-out data are not sufficient but are clearly very promising as :
It has been demonstrated that the propagation and larval rearing phases are relatively easy (even if the survival rates are not known with accuracy) : it lasts 60 hours only and the animals can apparently be fed with naturally produced algae ;
The animals appear strictly herbivorous and the required algae can be intensively produced without any difficulty ;
The animals are not agressive and occupy the whole volume of the cages (high production yields can be expected) ;
The production of 2 kg animals within 18 months would be an excellent result.
Under these conditions, the next step should be the implementation of a pilot project consisting of :
One onshore hatchery-nursery allowing a control of all the rearing parameters ;
Various large grow-out facilities such as floating cages or pens for solving the technological problems that will appear when passing to the level of large grow-out units. 2 years of operation of that pilot project appear necessary before starting a commercial project.
2.5.2. Production potentialities in Grenada and Carriacou
They are similar to those for seamoss culture and are described in section III, 2.4.2. Thus, there are large technical potentialities for that activity in Grenada and Carriacou.
2.5.3. Aimed market
From marketing point of view, the Caribbean King Crab is comparable to the Alaskan King Crab, and likely to command a similar price and use in the U.S.A. Thus the aimed market is the north american one.
2.5.4. Interest for the country
As previously described, it is clear that the King Crab culture is still in its enfancy and that the production process is not yet reliable enough to start a commercial production. However, the consultants team considers that this activity could be of considerable interest for Grenada provided a reliable production process be set up during the next pilot project phase.
The following elements demonstrate clearly the potential interest of that form of aquaculture for Grenada :
The aimed market is the north-american one ;
The animal is relatively easy to breed and to feed ; thus the chance of success during the pilot phase is very high ;
The animal feeds on algae. It means that :
1) there is no consumption of energy,
2) It valorizes the natural wealth of Grenada : pure marine water and sun.
There would not be problems for fishermen to shift to this activity as they are well used to the required manipulations (handlings on boat, diving, etc) ;
The grow-out activity would be accessible to many small investors as the initial inputs will remain limited.
GRIDS SLOWLY GETTING COVERED WITH NATURAL ALGAE
|Crab feeding on a grid|
OPENED FLOATING CAGE
|Grid covered with algae|
OPENING THE TOP OF A FLOATING CAGE
YOUNG CRABS FEEDING ON A GRID