Characterization of water quality in shrimp ponds of different sizes and with different management regimes using multivariate statistical analysis

Abstract

Coastal shrimp aquaculture in Bangladesh is mostly practiced in an agricultural unit called a Gher, which is a special type of agricultural field with elevated surrounding embankments/ borders situated by the side of a river that is used to grow rice in winter and shrimp in summer. Ghers of different sizes are managed in different ways. An on-farm project was carried out to study the effects of Gher size and their related management practices on water quality, shrimp production and the economic returns of shrimp farming in the Southwest coastal region of Bangladesh. We present here the results of this project with respect to water quality as explored through factor analysis, which was applied as a way to understand the nature and extent of the effects of different variables. For the majority of the variables and factors, one-half to two-thirds of their variability was explained by changes over time (months), and a further one-quarter to one-third was explained by Gher size and associated management practices. The alternating dry/monsoon season and water management practices determined long-term and large-scale (annual) water exchange in the Ghers that mainly affected processes related to live and dead particles suspended in the water column. Processes related to decomposition and nitrification were more dependent on short-term (days) water circulation in the Ghers, which is turn was reliant on the time span between the exchanges of water in the Ghers and river. Our results show that improved management leads to higher natural and shrimp productivity in the smaller Ghers and strongly support the argument put forward by the policy makers and scientific community in Bangladesh that the smaller the Gher, the better they can be managed and the better the possibility of increased shrimp survival and production.

Economic risk associated with white spot disease and stochastic variability in economic, zootechnical and water quality parameters for intensive production of Litopenaeus vannamei

“…Kongkeo (), Milstein et al . () and Islam et al . () indicate that small ponds allow better management and lead to increased growth, survival, yields and economic returns of P. monodon .…”

Effects of season on ecological processes in extensive earthen tilapia ponds in Southeastern Brazil

“…The large amounts of water entering the studied ponds bring in allochthonous materials, and lead to higher water exchange rates. Rain and large amounts of water inflows lead to low salinities and decreased electroconductivity (Milstein et al, 2005), as well as higher turbulence, which maintains materials suspended in the water column (reduced Secchi disc visibility). Turbidity and cloudiness (rain) reduce photosynthesis (Factor1+), hence dissolved oxygen, pH, chlorophyll-a, algal populations, and cladoceran grazers.…”

Stock model and multivariate analysis for prediction of semi-intensive production of shrimp Litopenaeus vannamei as a function of water quality and management variables: A stochastic approach

“…Small ponds have been recommended for improving shrimp cultivation; it is generally acknowledged that they can be stocked at higher densities, compared with large ponds Milstein et al, 2005;Ruiz-Velazco et al, 2010a,b). We did not find evidence that pond size affected growth and mortality of shrimp, yet because of the high stocking densities, the smaller ponds had higher production.…”