18. Double-cropping malaysian prawns, macrobrachium rosenbergii, and red swamp crawfish, procambarus clarkii.
J. of Applied Aquaculture, 1, (1), 1991, pp. 65-77
The objectives of this study were:
- to determine the effects of three crawfish stocking densities on survival, growth, and yield of prawns and crawfish cultured in a double-cropping scheme;
Prawns, Macrobrachium rosenbergii, and crawfish, Procambarus clarkii, were alternatively grown in ponds to determine if they were compatible and if total production could be increased. Brood crawfish were stocked into replicated ponds at rates of 0, 60, 120 or 180 kg/ha on 18 April.
Water was removed to encourage burrowing. Following this, rice was planted as forage. Post-larval prawns (0.02 g) were stocked 3 July in all ponds at 17,500/ha. Prawns in half the ponds were fed and those in the other ponds were not. Ponds were drained from 7 to 11 October. Prawn production ranged from 157 to 248 kg/ha; survival ranged from 69% to 88%, and average size ranged from 11 to 17 g. There was no significant difference (P > 0.05) between fed and non-fed treatments. The ponds were reflooded and crawfish were harvested by trapping from 15 January to 15
May. The average yield of crawfish ranged from 746 to 1,266 kg/ha.
Stocking rate had no effect on crawfisch yields (P > 0.25). Total yield, with prawns and crawfish combined, ranged from 1,037 to 1,237 kg/ha.
Overall, prawns and crawfish were compatible in rotation.
This study demonstrated that prawns and crawfish are compatible in pond production and that one crop of each can be produced annually in the same pond. To achieve this, pond management strategies had to be modified. For example, rice was planted as forage only in the shallow area of the pond, and a deep portion was left open for initial stocking of prawns. While the crawfish yield in ponds was acceptable (1,000 kg/ha), prawn yield was low due to small size at stocking (0,02 g), low stocking rate (17,500/ha), and short growout period (93 days).
The ongoing goal of most commercial prawn growers is to produce a large prawn (30 g+), but when prawns exceed approximately 17 g they begin to segregate into different size groups. Up to 17 g, there is virtually no size distinction, even between males and females. Successful marketing of such small individuals would produce additional revenue.
Crawfish are normally not available during summer and early fall, but prawns can be harvested during this period. The ideal size of prawns for molting troughs is about 17 g. Thus, prawns could possibly fill both a biological niche (rotation with crawfish in ponds) and a market niche (soft shell). Preliminary research indicates that prawns can be molted in the same shedding tanks as crawfish, and this could allow year-round production of a soft-shell product. The implementation of this would require new management strategies. Crawfish may have to be cultivated differently by introducing a formulated diet instead of allowing them to feed on rice forage. This management strategy could also produce a larger, more valuable crawfish (33 or less per kg), especially for the European market. Additionally, stocking systems will have to be developed to produce a 17-g prawn during those months when crawfish are normally not available. This study suggests that production of 17-g prawns is possible. Future research should concentrate on stocking dates, stocking sizes, stocking rates per hectare, and length of grow-out period.
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Asia, Malaysia, study, rice, fish, farming systems, resource utilization
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