The Caribbean Sea is defined as that area bounded by the Greater Antilles on the north, from Cuba to Puerto Rico, the Lesser Antilles on the east from the Virgin Islands to Trinidad, and on the south and west by the coastlines of South and Central America from eastern Venezuela to the Yucatan Peninsula (Powles, 1975). Its surface area is about 2 072 000 km2. The continental shelves of the islands are generally narrow (1 to 3 miles in the Lesser Antilles, and 5 to 10 miles in the Greater Antilles) and slopes to deeper water are steep. Those off the continent are more extensive, but the shelf is still less than 20 miles wide over long distances (Kawaguchi, 1971).
The Caribbean Sea lies within the trade wind belt. Most of the year wind velocity is 24 to 32 km/h from an easterly direction, but some variability in both speed and direction occurs during the summer.
Temperatures are moderate throughout the region and do not fluctuate greatly during the year. In Montserrat, for instance, the coolest average monthly temperature of 24.7°C occurs in February; during July, the hottest month, the average temperature is 27.2°C. There is greater range between day and night temperatures than there is between the mean temperatures of the hottest and coolest months. During the day, temperatures can occasionally exceed 33°C in the coldest months. Temperature during the night regularly drops to 21°C in the Lesser Antilles and to 18°C in the Greater Antilles. Temperature also varies significantly with altitude, falling about 0.6°C for every 91 m of elevation (Macpherson, 1979).
The Caribbean has a rainy season, but the difference between seasons is much less pronounced than in countries which have a monsoon. The north-east trade winds are humid, but they do not normally bring substantial rainfall, although light showers occur frequently. Annual precipitation varies greatly from place to place and at any given place varies from year to year as the following table of 10-year average rainfall values in Antigua illustrates (Macpherson, 1979):
|cm of rain||82.8||112.3||112.5||84.1||87.4||71.4||71.1||60.7||124.5||164.5|
Because of the rapid rate of evaporation a month is said to be wet only if its rainfall is over 10 cm. A month with under 6.25 cm of rainfall is said to be dry unless it follows a wet month (Macpherson, 1979). In an arid area like the southwest coast of Puerto Rico, evaporation rates vary from 250 to 400 cm/year; elsewhere an average value would probably be half of that (Powles, 1975).
The chief climatic hazards are drought and hurricanes. A long drought lasting for several months is a risk throughout the Caribbean. Many of the low-lying dry islands, including most of the Lesser Antilles and some of the Bahamas, have problems in supplying enough fresh water to their population. Barbados has large aquifers and has less problems than any of the other more populated islands. Due to their large size, the Greater Antilles have a more constant water supply, but nevertheless, rivers dry up seasonally in Haiti and Jamaica.
Hurricanes and tropical storms occur frequently in the Caribbean and cause widespread damage. A hurricane is a severe tropical cyclone with maximum winds of at least 32 m/s. Tropical storms have winds of less than 32 m/s but greater than 13 m/s. Hurricanes and tropical storms occur in almost every month, but primarily between June and October. All areas of the Caribbean may be affected, but more frequent and more severe storms occur in the northern portion. The highest probability of occurrence of a tropical cyclone is in the islands in the area between St. Lucia and the eastern part of the Dominican Republic. At least one tropical cyclone will pass through each 2 1/2 degree latitude-longitude square in at least 50 percent of the years. The frequency drops in the extreme southern Caribbean where storm centres pass less than once in 10 years in Trinidad (Gentry, 1971).
Tidal rise and fall is small throughout the Caribbean. The following table lists tides in some representative countries. The data is from Halsam, 1978.
|Antigua - St. John's||+0.2||+0.4||0.2|
|Dominica - Portsmouth||+0.2||+0.6||0.4|
|Haiti - Port-au-Prince||0.0||+0.5||0.5|
|Jamaica - Port Royal||+0.3||+0.5||0.2|
|St. Lucia - Castries||+0.3||+0.6||0.3|
1 MLLW = MEAN LOWER LOWER WATER (in metres)
2 MHHW = MEAN HIGHER HIGH WATER (in metres)
The Caribbean is generally deep, about 80 percent being deeper than 1 800 m and 50 percent deeper than 3 600 m. The shelf area, usually the most productive zone for fishing, is small, thus limiting the fishing grounds for demersal fish.
The surface water of the Caribbean is warm, varying between 26.5 and 28°C, and of normal oceanic salinity, 35 to 36 ppt.
Since the surface temperatures remain high throughout the year, the water column is stable and, consequently, there is little exchange of deep and shallow water, and nutrients from the deeper layers are not recycled into the surface layer. Soil is often poor and rivers are few (or on lower islands non-existent) with a result that run-off from rain adds only small quantities of nutrients to the sea. Nutrient contributions from mangrove estuaries, coral reefs and turtle grass beds are also low as none of these areas makes up a very large proportion of the total surface area of the Caribbean. The prevailing currents carry nutrients out of the region. Primary productivity is, therefore low, and is reflected in poor production of fish and other organisms at higher tropic levels in the food chain (Powles, 1975).
As is typical of tropical and sub-tropical waters, numerous species are present. More than 400 are taken commercially and 50 are commonly found in fish markets, but as already indicated most species do not occur in great number. Macpherson (1979) stated that in 1970 only one-fifth of the region's needs were supplied by local fisheries - the remainder had to be imported. Low productivity is, however, not the only reason.
Kawaguchi (1971) gave the following analysis of the problem:
‘The local fishing industries are small, using mostly the daily beaching type craft at numerous locations due to a small number of natural or man-made harbours. This results in limited landings at a given location and prevents further development of necessary facilities. The typical fishing methods are pot fishing, with some traditional handlining for demersal fish, and boat or beach seining for pelagic fish, which seasonally approach shore. Gill nets for longlines are employed seasonally in very limited areas. The dominant north-easterly trade wind of the region limits small craft operation to the inshore leeward portions of the islands from October to May, while hurricane threats limit their fishing range in the rest of the season’.
With the exception of Antigua, the fishery round most of the islands is largely dependent on seasonally migrating pelagic species which generally run from January to June (Kreuzer, 1978). The abundance of fish appears to fluctuate widely from year to year, and shore facilities are not adequate to store, market and distribute large intermittent catches (Kirwan and Espent, 1978). Increased supplies could be produced by better exploitation of the migratory pelagic species.
Demersal fish on most of the shallow inshore fishing grounds near populated islands are fished intensively and larger catches cannot be expected. However, experimental fishing on the continental slope depths indicates unexploited populations of deep water species which could be fished. Barbados, Trinidad and Tobago have established fisheries for flying fish.
In the northeastern Caribbean, expansion of the nearshore fishery is hampered by the occurrence of ciquatera fish poisoning. All of the commercially important bottom fish are occasional or common carriers of ciquatoxins. The greatest incidence of toxic fish is found in the Virgin and Leeward Islands. In these areas many restaurants are reportedly unwilling to run the small risk of serving customers a poisoned fish (Brownell, 1971).
Kirwan and Espent (1978) state that annual earnings of fishermen in the Commonwealth countries of the Caribbean range from about U.S.$ 555 for a fisherman/deckhand to U.S.$ 5 550 for a skipper-owner. Many fishermen do other kinds of work on a part-time basis to increase their income.
Fish forms an important part of the diet of most people in the Caribbean islands and imports of fishery products have always been high. The principal products imported have been dried-salted cod and pickled mackerel. This trade is decreasing as a result of increased prices on the international market. In Grenada, for example, the quantity of fish imported dropped by 50 percent between 1968 and 1977, but during the same period the value actually increased by 18 percent. The reduction in fish imports has been compensated, in part, by increased imports of cheap meat and poultry, but the result in many countries has been to reduce the total amount of protein available to the population.
A recent FAO document (FAOa:1980) presents estimates for demand of food fish in 1985 and 1990, taking into consideration population growth and changes in income. An extract is given in the following table:
Caribbean Supply (1975) and Estimated Future Demand for Fish
|Region||Supply 1975||Estimated Future Demand|
|Total Greater Antilles (excluding Cuba)||7.0||103||7.9||144||8.2||167|
|Lesser Antilles and others||21.1||63||26.0||89||27.0||98|
Specific information on the possibilities of increasing the marine fish catch for any one island is difficult to come by. It is believed that for the Caribbean as a whole it should be possible to increase marine fish catches from a 1978 total of about 1.85 million up to some 4 to 5 million tons. Large quantities of demersal fish caught by shrimp trawlers are wasted. Efforts by fishery workers in the region to find an economic way of using these resources have so far not been successful. The underexploited resources include coastal pelagic, schooling fish, but an effective and economic way of exploiting these stocks has not yet been developed.
Although the Caribbean islands have a distinctive regional character - for instance, similar agricultural crops are grown everywhere - they differ greatly in history, size and economic resources. Thus, Gross National Product per caput for 1978 was U.S.$ 260 in Haiti, U.S.$ 1 110 in Jamaica, U.S.$ 530 in Grenada, and U.S.$ 1 960 in Barbados (World Bank, 1980).
The economies of most of the Caribbean islands rest on agriculture and tourism. Some islands have minerals; bauxite and gypsum in Jamaica and Hispaniola; mineral hydrocarbons in Trinidad. Industrialization is, with few exceptions, insignificant.
Coffee, sugar and bananas are the main crops and account for more than half of export earnings in some of the islands. The extent of subsistence farming varies from island to island. In Haiti about 85 percent of the population are engaged in agriculture (and fisheries), mainly for subsistence. It is estimated that on average one-fourth of their production is traded. In Jamaica, on the other hand, only about one-third of the labour force is engaged in agriculture; industries and services being more developed.
Naturally, the widespread and large consumption of fish justifies investigation of the possibilities of aquaculture. However, some islands have a supply of marine fish from the local fisheries, as high as 25 kg per caput. In Haiti, on the other hand, it is below 1 kg/person/year (Table 2). No predictions of demand for the products of aquaculture can be valid for the Caribbean as a whole. The Greater Antilles are likely to present a stronger and more varied demand than would the Lesser Antilles.
Aquaculture, however, need not be confined to supplying fish to the local market. As a result of their tourist trade most of the small countries have good connections with North America and Europe, which might facilitate export of small quantities of high-priced marine products. In some of the smaller islands one might envisage culture of high-priced species for export (shrimps, marine fish) and import of lower-priced fish (small pelagics) for the local market.
Although the general lack of fresh water, along with high rates of evaporation, make fresh water pond culture difficult, even on the larger islands, sufficient water is available to support aquaculture in some areas. In most of the small islands however, it will not be possible to practise inland aquaculture on a significant scale. Construction of ponds could be very costly if they had to be excavated to depths sufficient to provide adequate reserves of water to compensate for evaporation. In many areas the surface soil is not deep and the sub-surface is rock. Additional complications arise from the annual irregularity of rainfall and the frequent droughts; in some years water supplies will not be sufficient to provide for the normal dry season, let alone unforeseen droughts.
The low tidal range means that coastal brackish water ponds cannot be filled and drained by tidal exchange; pumps would be necessary. However, the low tidal range favours pumping as the height to which the water has to be pumped is minimal and high volume pumps with relatively small energy requirements could be used.
Rapid evaporation from large brackishwater ponds would raise salinity to undesirable levels unless considerable amounts of water are exchanged regularly, as there is insufficient fresh water for dilution. Too frequent water exchange would mean that any nutrient fertilizers added to the ponds to increase productivity would be lost.
The frequent tropical storms with their high winds and heavy rains must be taken into account. Aquaculture facilities in, or adjacent to, the sea, must be of low cost so that they can be replaced readily. If not, the aquaculture business should be able to afford replacement costs. In a system like cage culture of marine fish the value of the farmed stock may be considerably higher than the culture facility. There is usually sufficient warning so that fish could be harvested in advance of storms, but means of disposal or storage would be necessary. Preference should be given to species for which seed stock is available for restocking during the storm season.
Another important factor is land-use. Many of the smaller island states do not have enough land area to improve agricultural production greatly and attempts to divert agricultural land to aquaculture would not be favoured. Due to its value for tourism and recreation the cost of land near the sea can be very high in the Caribbean. Mangrove areas are limited, even on the large islands. Considering the fact that a number of reef fish are dependent on mangrove or grass flats in the shallow bays as nurseries, care must be taken in their exploitation. Brownell (1971) reports that already the reclamation of shallow bays and mangrove forests for residential, resort and industrial development has eliminated many important nursery areas. Even on the larger islands mangrove ought not to be used indiscriminately. Construction of fish ponds should be restricted to the higher, further back portions of the mangrove which are the least productive nursery areas. In addition, other man-imposed factors like pollution from dredging, and municipal sewage and garbage dumping, have made some areas uninhabitable for many species of commercially important fish.
A possible problem for cage or raft cultures would be security from pilferage.
In several countries the small size of the fisheries service precludes radical innovation such as development of aquaculture. Whereas in some of the smaller islands there are only one or two professionals, they cannot be expected to possess the knowledge and experience, or the time, needed to evaluate potential opportunities for aquaculture and to implement decisions to start practical projects.
Some services are not even strong enough to solve the technical problems associated with modernization and development of small-scale artisanal fisheries, and if no specialist advice is obtained on aquaculture it might be that those countries that can afford to strengthen their fisheries services will have small-scale marine fisheries as their first priority rather than aquaculture development quite irrespective of the merits of one or the other.