Water quality suitability and water use indices: Useful management tools in coastal aquaculture of Litopenaeus vannamei

Abstract

Attempts were made to study the effect of stocking density and water saving approach on water and sediment quality, growth and production performance of shrimp (Litopenaeus vannamei). The experiment was carried outwith three stocking density of post-larvae i.e. 400,000 per ha (T1), 500,000 per ha (T2) and 600,000 per ha (T3).Water exchange was carried out depending on water quality parameters. Water quality suitability index (WQSI) was lower at higher stocking density as was evident in T3 followed by T2 and T1. A very good WQSI (7.5–9.0) was recorded up to 13th, 12th and 9th week of culture in T1,T2 and T3, respectively; which was ascribed to stocking density, smaller shrimp size and less initial feed input. In L. vannamei culture, optimum stocking density of 50 post-larvae per m2 (T2) led to total water use of 3.42 × 104 m3 and water exchange of 0.80 × 104 m3. It was perceived as a way to improve shrimp productivity (10.31 t/ha 120/d), consumptive water use index (1.93 m3/kg biomass), total water footprint (1426 m3/t biomass), net consumptive water productivity (USD1.13/m3) and ratio of output value to the cost of cultivation (1.99). Further, farming systems with low to moderate water exchange as in T2, helped maintain water quality suitable for the shrimp growth, improved water use efficiency (518 g biomass/m3 water), minimized quantity of sediment load (41.7 m3/t biomass) and effluent outputs (0.8 × 104 m3). The knowledge derived from this study could provide the basis to optimize pond rearing efforts in shrimp culture and the water management strategies can be tailored to minimize production costs.Statement of relevance: This paper presents findings and analysis, from a methodologically rigorous investigation and provides insight regarding density-dependent optimum water use, its effect on pond water quality, sedimentation rate, growth performance, water productivity and water footprint. The knowledge derived from this study may be a basis to optimize pond rearing efforts in shrimp culture and the water management strategies can be tailored to prevent wasteful use of water and enhance water use efficiency and water productivity.