INTRODUCTION

Though freshwater prawns were collected from the wild and on-grown to market size in impoundments earlier, true culture systems began to be developed after 1962. Pioneer work by Shao-wen Ling in Penang, Malaysia, succeeded in closing the life cycle (Ling, 1977) of the giant long-legged prawn, Macrobrachium rosenbergii, stimulating widespread interest in the commercial potential of culturing this and other members of the palaemonid family of crustacea. Enthusiasm for the culture of this genus was infectious, sometimes with scant thought about the potential markets for freshwater prawns. This was spurred by the fact that, at that time, it had not been possible to close the life cycle of marine shrimp, for which there was an established global market.

In 1965–1966 Macrobrachium rosenbergii was imported into Hawaii, where Takuji Fujimura and his team at the Anuenue Fisheries Research Centre developed mass rearing techniques for larval production (Fujimura and Okamoto, 1972). Successful grow-out experiments in Hawaiian ponds were soon followed by early attempts to establish commercial farming of this species in many other places, including Australia and Mauritius. For several years it was Hawaii that remained principally linked with freshwater prawn culture in the columns of the aquaculture press. Meanwhile Thailand, a country with a tradition of freshwater prawn consumption, was quietly probing the possibility of Macrobrachium rosenbergii culture; this fact was little known outside that country at the time. The third pioneer in establishing commercial prawn culture was Taiwan. Although M. rosenbergii had been occasionally found naturally in southern Taiwan, it was two adults imported from Thailand in 1970 that led to the development of freshwater prawn farming (Chen, 1976).

Recent estimates of the aquaculture production of Macrobrachium rosenbergii are provided in Table 1. By the middle of the 1980's global production was over 20,000 mt/yr. 73 per cent of this total was farmed in Thailand and 17 per cent in Taiwan. In 1987, Thai freshwater prawn production was estimated to be 15,000 mt/yr. Macrobrachium (principally M. rosenbergii) culture is in the experimental or low-level commercial phase in many countries. These include Australia, Bangladesh, Burma, Ecuador, Indonesia, India, Jamaica, Japan, Nepal, the Philippines, Puerto Rico, South Africa and Sri Lanka. The estimates (Table 1) of production, based on various sources, of 750 mt/yr and 600 mt/yr for Brazil and Mexico in 1986 may be under-estimates. 1987 prawn production in Brazil and Mexico probably markedly exceeds the figures given in Table 1.

By 1979 the pioneering research and development of the Chacheongsao Fisheries Station led by its chief, Somsak Singholka, had stimulated a national prawn aquaculture production of 80 mt/yr in Thailand. In 1976 it had been only 3 mt/yr (Boonyaratpalin and Vorasayan, 1983). By 1980, strengthened by a UNDP/ FAO project headed by the author, freshwater prawn farming had spread to 40 of the 72 Thai provinces (New et al., 1982). In 1980, a team studying the economic status of freshwater prawn farming in Thailand reported that it was a profitable activity for both hatchery and pond production in all sizes of farm units examined (Anonymous, 1980a). By 1982 the number of prawn farms had increased to 677 with a total area of 1,737 ha (Boonyaratpalin and Vorasayan, 1983). A further 9 of the Thai provinces contained prawn farms. Average annual pond yield was 750–1,500 kg/ha in 1982 and national production had grown to more than 1,200 mt/yr (Boonyaratpalin and Vorasayan, 1983). In 1983 Thailand was still importing 700 mt/yr of prawns, mostly from Burma. Since 1982 prawn farming has continued to expand, with 1986 production being more than 4,000 mt (Janssen, 1987), with an estimated farm-gate value of US$ 16 million/yr. In 1987, Thai production was estimated to be 15,000 mt (S. Singholka, personal communication, 1988) of which one-third was exported to Europe. Cultured prawn production has not yet exceeded 800 mt/yr anywhere else except Taiwan (Table 1).

Initially rapid expansion of this type of aquaculture was later overtaken by the growth of marine shrimp farming in Taiwan. The latter developed in response to the global demand for the product and as a result of a break-through in rearing technology (Liao, et al., 1969). However freshwater prawn culture, which was 65 mt/yr in 1979 (Liao and Chao, 1982), had increased to 3,500 mt by 1986 (I-C. Liao, personal communication, 1987). Total Taiwanese production of marine shrimp exceeded 15,000 mt/yr by 1983 (New and Rabanal, 1984), while production of Penaeus monodon alone exceeded 18,000 tons in 1984 (Chiang and Liao, 1985) and total farmed shrimp production was said to be 40,000 mt in 1986 (Hopkins, 1986).

The history of freshwater prawn farming in Hawaii can be followed in the pages of a publication called Aquaculture Digest. There, as in Thailand, initial growth of the prawn farming industry was stimulated through the free distribution of postlarvae from 1965 onwards by a government hatchery for stocking into commercially owned ponds. However, by 1978, farmers were also turning to private hatcheries for supplies or establishing their own hatcheries. Large private hatcheries, by 1981, were claiming that irregular state hatchery production was distorting profitability figures. In 1980 there were at least 24 prawn farms in the State. One of the largest farms built in Hawaii was the Lowe Aquafarm. In 1981 this farm was reported to be harvesting at the rate of 83 mt/yr, but disappointments were being voiced about the less-than-expected growth of the industry in the State generally. By the end of 1981, total Hawaiian prawn production was only 118 mt/yr, whereas it had been predicted 3 years earlier that it would be 1,000 mt/yr by then. Economic viability, market potential and bureaucratic problems were blamed. Lowe Aquafarm (now renamed Amorient Aquafarms) was a 150-acre farm by 1983. It was then said to be making a profit on a production of 5.4–7.7 mt/month. In 1984 it produced 79 mt but in 1985 production fell to about 68 mt; then it was reported that it had ‘never made a profit’ and that its owners intended to convert the farm to marine shrimp culture. Since then, the farm has been for sale, its owners having decided to concentrate on marine shrimp farming in Ecuador. Though many smaller freshwater prawn farms remain in Hawaii, this account of the rise and fall of the largest farm illustrates the contrast between Hawaii and Thailand. Hawaii had neither the abundant sites, nor the cheap labour, nor the large home market accustomed to freshwater prawn consumption that Thailand had.

Table 1. Countries reported to be active in prawn culture in 1987

¹ Ac = M. acanthurus;
Am = M. americanum;
C = M. carcinus;
L = M. lanchesteri;
M = M. malcolmsonii;
O = Other Macrobrachium spp.;
R = M. rosenbergii;
V = M. vollenhovenii

² Production data, from various sources in mt/yr in 1984 or 1985 except when otherwise stated
³ See French Caribbean for total
⁴ See text
⁵ Includes Hawaii. However Premaratne et al., (1986) state that Hawaiian production was 150 mt/yr in 1985.

Elsewhere in the United States enthusiasm for freshwater prawn farming has been manifested by research and development by state governments, universities and entrepreneurs which included seasonal farming in southern states (South Carolina, southern Georgia, Mississippi, Louisiana, Tennessee, and Alabama, in mono- and polyculture), geothermal farms in Idaho, Nevada, Oregon, and California, thermal aquaculture in New Jersey, South Carolina and Oregon, and solar heated recirculating systems in Rhode Island. Despite these activities, the total commercial production of freshwater prawns in the United States remains minimal. The contribution of the continental U.S. has been principally in research, although Sandifer and Smith (1985) report the presence of at least one large commercial prawn farm.

U.S. companies are also involved in prawn farming outside the USA. These ventures include Puerto Rico, where the Sabana Grande Prawn Farm had developed 35 of its 142 hectares by 1986 and built a hatchery; harvesting rates were then nearly 4 mt/month and were expected to double shortly. Another U.S. company, General Mills, Inc. had a pilot prawn farm in Honduras. Covenant Aquaculture Corporation plans to set up an 85-ha prawn/tilapia farm in southern Georgia, USA, scheduled to produce 180 mt/yr of prawns, based on Israeli technology developed by Aquaculture Production Technology. The latter company exports prawns from Israel to Europe and has also been involved in prawn farms in Jamaica, Ecuador, the Dominican Republic and the Philippines. A Dutch-UK company, Unilever PLC began a freshwater prawn farm in Sri Lanka but is now concentrating on the development of marine shrimp farming there and elsewhere in the Indian subcontinent.

Early (pre 1976) research on Macrobrachium spp. indigenous to Latin America has been reviewed by New (1980a). Currently, the Dominican Republic is rapidly expanding its prawn farming industry. In 1985 248 mt/yr were produced from 32 farms totalling 65 ha; by 1987 there were said to be more than 60 farms (Aquaculture Digest, 12.9.9.). By the end of 1986, there were 76 prawn farms in Martinique, Guadeloupe and French Guyana (Anonymous, 1987). The total area in production was said to be 152 ha, producing 133 mt/yr. Some ponds, which are run under continuous cultivation (some have not been drained for 5 years), produce 2.8 mt/ha/yr (Aquaculture Digest, 12.9.11). Guadeloupe farms average 1.0 mt/ha/ yr; there were 18 farmers and 48 ha of ponds in 1986 (Anonymous, 1987). Martinique produced 50 mt from 42 ha (1.2 mt/ha) and French Guyana 35 mt from 64 ha (0.5 mt/ha).

In summary, the commercial development of prawn farming is geographically broad but piecemeal and, with a few exceptions, nationally insignificant in terms of volume production. Research and development interest remains high but the large-scale expansion of freshwater prawn farming which was expected in the late 1970's has not materialized. This is due to a combination of factors which include marketing and technical difficulties. A sound global commodity market for freshwater prawns has not yet been developed. However, the increasing export of freshwater prawns from Thailand to Europe may be the early indication of global market development. On the technical front the territorial nature of prawns and their longer larval life make them less attractive compared to marine shrimp, now that the difficulties associated with the captive spawning of the latter are being resolved. A summary of the countries known to be involved in prawn culture has been provided in Table 1.