Use of multiphase systems as a production tool in shrimp farming.

Shrimp production includes either direct stocking of post-larvae (PLs) into grow- out tanks until they reach marketable size (single-phase system) or stocking of PLs into transitional tanks (nursery ponds/tanks) followed by final transfer to grow-out ponds/tanks (Samocha and Lawrence, 1992). This culture system is defined as a two-phase system (Lawrence et al., 1985 and Lawrence and Hunter, 1987) when only a nursery phase is included and three-phase system when an additional pre – grow out phase takes place within the shrimp's grow out strategy. 

Multiphase systems are often adapted to fit a specific production plan and process flow which may change with respect to species characteristics, climate, facilities design and economic environment. There are many types of nurseries, including earthen ponds and /or floating nets (Apud et al., 1983; Aquacop, 1985; Issar et al., 1987; Seidman and Issar, 1988; Villalon, 1991 and Sturmer et al., 1992), tanks (Kumlu and Eroldogan, 2000), and raceways (Stern and Letellier, 1992).

The most important advantages of multiphase systems are: 1) provide an accurate estimation of biomass for stocking into grow-out ponds, 2) control of predators and competition, 3) crop predictability, 4) better utilisation of farm infrastructure and resources, 5) reduce feed waste (Aquacop 1985; Fast, 1991; Sturmer et al., 1992 and Hirono, 1983), 6) high survival (85- 95%), 7) production of larger and robust juveniles for stocking into next phases (Sturmer et al., 1992), 8) decreases the grow out period allowing to more than one production cycles per year (Samocha et al., 1990; Fast 1991and Clifford, 1985 & 1992;), 9) more uniformity in shrimp size at harvest, 10) better control of pathogens and treatment for diseases, 11) reduced risk management with stocking small sizes of shrimp fry (Stern and Letellier, 1992).

Therefore, a multiphase system could be considered as a production tool that helps to optimise shrimp farming operations using more efficiently the resources and maximising the production area while improving the productivity and sustainability of the business.