The feasibility study concerned the districts of Thatta and Badin, in lower Sindh province. Thatta district borders both banks of the Indus River, whilst Badin lies to the east of Thatta. The mangrove swamps of the Indus Delta which lie within the districts concerned in this study are said to include some 385 000 ha of inter-tidal lands considered suitable for (marine) shrimp fanning. Winter air temperatures in Sindh range from 10°C to 30° C, while summer temperatures range from 25 °C to as high as 50° C. Extremes of water temperatures are, of course, more narrow, but have already been shown to constrain the period when marine shrimp culture is viable (see Sections 3.1. and 4.1.).
Of the Indus Delta 6 400 ha was allocated to the private sector for shrimp farming. A 12 ha intensive farm, established by Lipton Pakistan Ltd., was one of the few options taken up. Activities at the Lipton farm have since been discontinued, due to the lack of hatchery-reared shrimp for stocking, despite reports that production levels of up to 2.5 t/ha were achieved.
The Thatta district also includes the government pilot shrimp farm at Garho, which was established by the Government of Sindh at a total cost of PRs 32.7 million (approximately $US 1 million) as part of the first Asian Development Bank (AsDB) Aquaculture Development Project, to demonstrate semi-intensive technology. According to the answer to a question raised in the Senate during June 1995, the results achieved were not up to the mark because of many reasons, including topographical conditions and the lack of feed and seed (the project did not include a hatchery). It was intended that the project should be revamped during the second AsDB Aquaculture Development Project. However, the pump house and the jetty collapsed into the sea and the project totally stopped functioning in 1990. When the second AsDB Aquaculture Development Project was extended in June 1994, the donor declined to provide further financing for the facility or its operation. Further details on this site are provided in Section 5.1.
The closure of the Garho shrimp project has undoubtedly caused a set-back in plans to develop shrimp farming in Pakistan, having instilled little investor confidence. The government is still anxious to revamp the farm, possibly in conjunction with the National Institute of Oceanography (NIO) or the University of Karachi.
In a determined attempt to address the lack of hatchery-reared seed, which was said to be a strong factor inhibiting the development of marine shrimp farming in Sindh, the GOP has approved a project for the establishment of a hatchery complex for the production of marine shrimp and finfish seeds. This project is now being implemented by the MFD. A site has been selected at Hawkes Bay, some 15 km west of Karachi and, at the time of the consultant's visit, construction was about to commence. The project is currently financed for three years with a budget of PRs 18.9 million ($US 551 825).
Total aquaculture production in Pakistan is more than 13 000 t, with a value in excess of $US 14 million (Table 1). Nearly all production is of cyprinids. The consultant was unable to substantiate the output of farmed marine shrimp which the GOP has provided for inclusion in FAO statistics (FAO, 1995). Carp culture has been fostered by the government and through the two AsDB Aquaculture Development Projects. The GOS currently has two freshwater finfish hatcheries, one of which is in Thatta district, at Chilya, near Thatta town. A third hatchery is being constructed near Badin town.
Aquaculture contributes a substantial proportion of the total production of freshwater finfish in Sindh (Table 2). Declining capture fisheries and increasing aquaculture output have combined to increase the contribution of aquaculture from 16% in 1992 to 22% in 1994. The proportion of cultured fish produced in Sindh contributed by the Thatta and Badin districts is rising, being more than 50% in 1994. Aquaculture production consists of three Indo/Pak major carp species, together with common carp (Table 3). Rohu (Labeo rohita) is the dominant species (35%).
In 1994 there were 1 350 fish farms in Sindh, which together produced nearly 13 000 t of fish (GOS, 1995). In 1993 there were 1 327 farms; 42% were in the districts of Badin and Thatta, where freshwater prawn fanning is now being considered. A substantial finfish aquaculture industry therefore exists in these districts, and several fish farmers have indicated a desire to diversify into prawn fanning when reliable seed supplies become available.
Several experiments on the grow-out of an indigenous prawn species (Macrobrachium macolmsonii) have been conducted in Sindh (Yacoob 1994b; 1996). Wild seed, collected from Koti Barrage, were used for stocking the ponds. These experiments were conducted by PARC, with the cooperation of two farmers, in Mirpur Sakro and Chilya, both in Thatta district. A small grow-out experiment with the same species was also conducted in Islamabad (Yacoob, 1994a), which demonstrated a seasonal limitation in that area; prawns died when water temperatures fell to 7° C. Preliminary work on the larval rearing of this species was also conducted in Islamabad (Yacoob 1987).
The grow-out experiments with M. malcolmsonii in Sindh provide useful information on environmental conditions (Table 4), in addition to contributing knowledge on growth rates (Table 5). Growth rates with the proposed species for commercial culture (M. rosenbergii) should be at least as good as those obtained in the experimental work with M. malcolmsonii.
In Thatta district (Table 5), survival rates of M. malcolmsonii ranged from 32% to over 75 % in the first trial, when animals averaging 0.5–2.0 g were stocked. In the second trial, which employed larger juveniles (3.5–8.0 g), survival ranged from 52% to 69%. Average harvest weights of 47.5–83.5 g were achieved in the first trial and 30–63 g in the second. Stocking rates were quite low (0.5–2.5/m2). Average daily weight increments ranged from 0.17 g/day to 0.38 g/day. Productivity ranged from a minimum of 217 kg/ha to a maximum of 1 038 kg/ha. Interestingly, the pond which gave the greatest yield was stocked with 1 g juveniles at the highest stocking density used (2.5/m2) and the rearing period was the shortest (138 days). Prawns in this pond were reared from mid-July to the end of November, thus avoiding the cooler winter months.
Extrapolating from these results it is reasonable to expect that, using 3 g juvenile M. rosenbergii stocked at 5/m2, average yields of 1.5 t/ha should be achievable in 6 to 8 months, depending on the season in which the animals are stocked. It is not yet clear whether annual productivity can be increased by stocking ponds more than once per year, or by operating a continuous stocking and harvesting regime. For the moment, potential yield is therefore set at 1.5 t/ha/year.
Specific grow-out sites for the commercial culture of prawns in Thatta and Badin districts were not evaluated, since the feasibility study was confined to the establishment of a government hatchery and demonstration farm, and travel outside Karachi was extremely difficult (see Section 1.3.). However, some consideration was given to this topic, since there is no point in demonstrating the technology for prawn farming if there are no suitable sites for commercial culture available.
Considering the large and expanding number of finfish farms in these districts (Section 3.2), which are achieving reasonable productivity (about 2 t/ha/year), it is reasonable to suppose that adequate and suitable sites where prawn farming could be practised in these districts are available. Prawn farming will not have significantly different requirements for resources, including land, water and feed ingredients, than carp culture.
The production of hatchery feeds requires only simple kitchen equipment, while adequate grow-out feeds can be made in existing compound feedstuff mills. Initially, compound chicken feeds can be used for this purpose, although they are not ideal, either in composition or water stability. However, the requirements of intensive marine shrimp fanning for both feed ingredients and feed production technology, are much more demanding. It is anticipated that the GOP will require substantial technical assistance in this field, at which time it would be appropriate to consider freshwater prawn feeds also. In 1984, the present consultant provided advice on farm-made feeds for semi-intensive marine shrimp culture to the shrimp component of the first AsDB Aquaculture Development Project, which could easily be adapted for the production of farm-made feeds for freshwater prawns.
Some enthusiasm for prawn culture already exists, both amongst existing finfish farmers and new entrants to this sector. The consultant met several potential prawn farmers during his mission, two of which had collaborated with Yacoob (1994b; 1996) but had not progressed further because of the lack of seed. The establishment of prawn fanning in Sindh would create increased income, opportunities for investment, and employment opportunities.
Data from the two sites used for experimental prawn culture indicate no environmental barrier to prawn culture in the area under consideration (Table 4). Although only seepage and evaporation losses were replaced and no aeration was provided, dissolved oxygen levels appear to be satisfactory (however, the relationship between the ranges of DO2 and temperature summarized in Table 4 is not clear; some degree of super saturation appears to have existed), pH remained within the desirable range throughout all the experiments and in all ponds.
Average temperatures were satisfactory. However, a minimum water temperature of 13° C and a maximum of 38° C were recorded in the Thatta ponds, though generally the extremes were from 17° C to 36° C. Yacoob (1994a) observed complete mortality when water temperatures in Islamabad fell to 7°C, although it is not known whether prawns had already died at somewhat higher temperatures. The extremes recorded in Thatta district, Sindh (13° C and 38° C) are close to the temperatures regarded as lethal for prawns. However, this does not present an insuperable obstacle to the development of prawn culture. Problems due to excessive temperature can be avoided by skilful pond management (water exchange; aeration). Exposure of stocks to low temperatures (whether those possibly close to the lethal level or those at which growth rate will be depressed) could be minimized by stocking early enough to ensure harvesting occurs before winter starts. Despite the extreme water temperatures of 13° C and 38° C which were recorded (Table 4), experimental survival rates were satisfactory (Table 5), even when the rearing period included mid-winter or mid-summer. This augurs well for successful commercial culture but, as a cautionary approach, it is not envisaged that more than one production cycle per year will be possible. Despite this, as indicated above, a yield of at least 1.5 t/ha/year should be achievable.