Project summary

Aquaculture has known benefits to society, such as increased availability of high-quality animal protein, poverty alleviation, increased employment, foreign exchange earnings for developing countries, and profit for entrepreneurs and investors (Tucker et al., 2009a). However, most forms of aquaculture are perceived to have adverse environmental effects (Tucker et al., 2009a). Even though there are signs that the rate of growth for global

There have been concerns about the low rate of adoption of best management practices (BMPs) aimed at improving water quality (Valentin et al., 2004). A possible explanation for this reluctance is that farmers are uncertain of the impacts of adopting these BMPs on farm profitability (Valentin et al., 2004). Additionally, resources are scarce (Alston et al., 1998), and all governments and foreign aid donors need to justify their investments. However, the economic value of public investments may not be obvious (Masters et al., 1996; Antle et al., 2010). This difficulty is because economic impacts of projects are widely spread out, both spatially and temporally.

The impacts of the adoption of several technologies have been studied, with varying results (e.g. Valentin et al., 2004; Qaim, 2006; Antle et al., 2010; Dey et al., 2010). Impact assessment can be grouped into two types: ex-post studies, for technologies already being used, and ex-ante studies, for technologies not yet adopted (Masters et al., 1996; Antle et al., 2010). Ex-post impact assessments are believed to be more reliable than ex-ante assessments, because the former involves actual surveys, whereas the latter must rely on researchers’ trials and extrapolations (Masters et al., 1996). In both cases, however, the success of impact assessments depends on the judgment of the researchers in designing the survey, and collecting and interpreting their data (Masters et al., 1996).

An ecosystem service represents the benefits human populations

aquaculture may have peaked, high growth rates may continue for some regions and species, such as the sub-Saharan African region and tilapia (Oreochromis niloticus), respectively (FAO, 2007). These are usually small-scale operations in earthen ponds, which are fed with inexpensive and easily accessible sinking pelleted feed, and drained after every production cycle (Frimpong et al., 2009). Practices that enhance the profitability and efficiency of these small-scale aquaculture operations while protecting the environment must be encouraged.

Best management practices (BMPs) are increasingly regarded as meaningful goals in the overall reduction of cumulative impacts of agriculture (Clay, 2009). The two BMPs to be examined in this study are water reuse, and use of pelleted, floating feed (as opposed to sinking feed). Water use is inextricably tied to issues of waste discharge because increasing water input volume will increase water discharge volume (Tucker et al., 2009b). Also, wastes from uneaten feed and excreted nutrients are potential sources of pollution if effluents are discharged from the facility, even though nutrients function as fertilizer for primary production when left within the system (Tucker et al., 2009b). Therefore, the reuse of water by a farmer effectively prevents the export of sediment and nutrients from his ponds into effluent-receiving streams for those cycles that old-production water (water from a previous production cycle being used for fish culture) is employed.

Most manufactured feed meets high quality standards, but poor feeding practices can negate benefits offered by the feeds (Tucker et al., 2009b). Also, avoidance of feed wastes saves cost and contributes to farm profitability (Engle and Valderrama, 2004). Therefore, if a farmer can observe the feeding activity of fish and adjust feeding rate accordingly, pond water quality is improved and feed costs are cut. Extruded, floating feed allows the farmer to observe the feeding activity of his fish in order to make the necessary changes to his feeding regime.

derive from ecosystem functions (the habitat, biological or system properties or processes of ecosystems), such as waste assimilation (Costanza, 1997). The Minimum Data Method of the Tradeoffs Analysis by Antle and Valdiva (2006) has been shown to have several uses. It basically models the supply of ecosystem services (from an innovation, such as a BMP) from the spatial distribution of opportunity cost of providing those services. From this model, the rate of adoption of the BMP and the changes in social welfare and farm profitability in a region, as a result of the adoption of the BMP, can be determined (Antle and Valdiva, 2006; Antle et al., 2010). For this study, the amount of sediment (total suspended and settleable solids) and nutrients (nitrogen and phosphorus) that is prevented from entering effluent-receiving streams will represent the ecosystem service being supplied from the adoption of the BMPs under consideration.