Hatchery culture of Macrobrachium rosenbergii (cherabin)
Introduction
The giant freshwater prawn Macrobrachium rosenbergii occurs in freshwater rivers in the tropical Indo-Pacific region, extending to Northern Australia. Aquaculture of the species in 37 countries produces about 30 000 tonnes of prawns per annum. In Australia, no commercial venture has successfully established hatchery production of juveniles in the north, despite several attempts (Morrissy 1983). Robert Emiliani operated a successful pilot hatchery at Independent Seafoods' establishment in Perth during 1992 and this report describes a spawning and larval rearing trial at the Western Australian Marine Research Laboratories (WAMRL) in 1993.
The early, planktonic larval life of the species is dependent on brackish-water (estuarine) levels of salinity for survival, unlike, longer post-larval juveniles and adults which live entirely in freshwater. Adults breed very readily during the summer wet season and in captivity; however, the larvae develop through 11 stages, requiring a moderate level of hatchery technology and considerable husbandry skill for rearing (New and Singholka 1982; New 1988; Thompson pers. comm.).
Materials and Methods
Juvenile stock were collected from the Ord River near Kununurra in Western Australia during March 1992, flown back to Perth and housed at WAMRL. The identity of the prawns was later confirmed, as adults, as M. rosenbergii : the only, of several, Australian species of the genus Macrobrachium for which the inner pair of spines adjacent to the telson is shorter than the telson is rosenbergii (Morrissy 1983).
The stock were maintained in a fibro-cement tank (1530 x 740 x 380 mm) with an undergravel filter, a shell grit substrate and a constant flow-through of heated, freshwater (bore), to give water temperatures of 26-30°C. The prawns were fed five days per week on trout pellets, steamed-rolled lupins, fish and mussels.
On 2 March 1993, one female of 15 cm total length (tail to rostrum) was newly berried, with bright orange-coloured eggs. This female was left in the stock tank until the eggs changed to a greyish brown colour about 2 weeks later, when it was placed alone in 60L of freshwater in an 81.5 L glass aquarium (740 x 290 x 380 mm) and the salinity was raised from freshwater to 12o/oo. (parts per thousand = g/L) with seawater over the first hour. The planktonic, backwards-swimming larvae hatched out three days later on the night of 17 March 1993 and the female was returned to the stock tank. An estimate of the number of larvae released was 18 000: a female of this size has between 10 000 and 30 000 eggs (New and Singholka 1982). Approximately 12 000 larvae were siphoned off into a 120 L larval kreisal tank (Chang and Conklin 1983). A flow-through of brackish water maintained an exchange rate of 10 changes per day, which was later reduced to 2 changes per day to retain the larval feed of decapsulated, brine shrimp nauplii for a longer period. The remaining larvae were left in the glass aquarium (density 100/L) with no flow-through of water, but half the water was changed daily at cleaning.
Water temperatures were maintained by aquarium heaters (Rena 200W) and water was recirculated in the kreisal tank with a small pump (Rena 240V 10L/min). Salinity was measured daily with a hand-held refractometer (American Optical Corporation).
Artemia (brine shrimp) cysts (Argentemia grade 2 lot # 0710f411) were decapsulated in 1 litre Imhoff settling cones, according to the method outlined by Bruggeman et al. (1980), and then hatched in 5L cone-bottomed containers, filled with brackish water (12-14o/oo). The feeding of Artemia nauplii to the prawn larvae was commenced 24 hours after the hatching, at a rate to give 5 000 nauplii /L in the aquaria and 9 000 nauplii /L in the kreisal tank. Artemia nauplii were provided twice daily to maintain these concentrations until day 20 when small amounts of minced fish and very small amounts of ground trout pellets were also added up to 4 times per day with Artemia reduced to 1 feed at night. At this time, water flow was increased to 10 changes during each day, to prevent fouling by the fish flesh, and reduced to 2 changes at night to retain the Artemia nauplii. The larval units were cleaned daily by turning off all aeration and water flow for a short period to allow the settling of uneaten feed, fecal matter and debris which were then siphoned off the floor. The siphoned material was placed on a sieve and checked daily from day 15 for post-larvae. On day 21 the larvae from the aquarium were added to the kreisal tank.
Larval stages were identified according to the morphological descriptions provided by Uno and Soo (1969). For recording rate of development, the latter workers observed the mean number of days taken by individual larvae (12-50) to attain each stage; in this trial, a mean stage was calculated for a day from the stages of individuals in a sample taken from the tank (Dr R. Thompson, pers. comm.).
The first, settled post-larvae (PL) appeared on the siphon sieve on day 23. PL from the sieve were placed into a stock tank. A large number of PL (2500) were visibly present in the kreisal tank on day 34 and the tank was drained; the larvae and PL were placed on a sieve and then resuspended in a small tank where the larvae were separated out from the PL, which were counted and placed into a stock tank. The larvae were returned to the kriesal tank for a further 2 days of development, after which 200 PL were found and placed in the stock tank; the remaining (300) larvae were discarded. Usually when the majority of larvae have settled the whole batch is transferred to a nursery (New and Singholka 1982).
Results
The mean water temperature of 28.0 oC (sd 0.88) and salinity of 14.3o/oo. (sd 2.3) were comparable to those used by Uno and Soo (1969), i.e. 28.0 oC (sd 0.5) and 6.58-6.81o/oo.
Table 1 compares the development rate of the larvae in this WAMRL trial with that found by Uno and Soo (1969).
| Table 1. Development rate of Macrobrachium rosenbergii larvae. | ||
|---|---|---|
| Days from hatching | Stage | |
| Uno & Soo (1969) | WAMRL | |
| 0 | 1 | 1 |
| 2 | 2 | 2 |
| 4 | 3 | 3.2 |
| 7 | 4 | 4.4 |
| 10 | 5 | 5.7 |
| 14 | 6 | 6.9 |
| 17 | 7 | 7.4 |
| 20 | 8 | 8.1 |
| 24 | 9 | 8.8 |
| 28 | 10 | 8.9 |
| 31 | 11 | 8.9 |
| 34 | 9.8 | |
| 36 | PL | 11.9 |
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| Figure One - Stages of growth | |
References
Bruggeman, E., P. Sorgeloos and P. Vanhaecke. 1980. Improvements in the decapsulation technique of Artemia cysts. In the Brine Shrimp Artemia. 1980. Vol 3. Ecology, Culturing, Use in Aquaculture. G, Persoone, P. Sorgeloos, O. Roels and E. Jaspers (Eds). Universa Press, Wetteren, Belgium.
Chang, E. S. and D. E. Conklin. 1983. Lobster (Homarus) Hatchery Techniques. In CRC Handbook of Mariculture Vol. 1. Crustacean Aquaculture. J. P. McVey (Ed).
Morrissy, N. M. 1983. The potential of freshwater prawns in Australia. Proceedings of the first Freshwater Aquaculture Workshop, Narrandera, 21-25 February, 1983. pp 99-107.
New, M. B. 1988. Freshwater Prawns: Status of Global Aquaculture, 1987. Bangkok, Thailand: Network of Aquaculture Centres in Asia, 1988. iii, 58 p. (NACA Technical Manual; 6).
New, M. B. and S. Singholka. 1982. Freshwater prawn farming. A manual for the culture of Macrobrachium rosenbergii. FAO Fisheries Technical Paper No. 225. (Revision 1, 1989 is available from Hunter Publications in Collingwood, Victoria).
Thompson, Dr R. K. Personnal communication, March 1985.
Uno, Y. and K. C. Soo. 1969. Larval development of Macrobrachium rosenbergii (De Man) reared in the Laboratory. Journal of the Tokyo University of Fisheries, 55 (2) 179-190.
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| Figure Two - Survival of Larvae |
Produced July 1993 - Chris Bird, Research Services Division, the Department of Fisheries
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