The estimated total economic impact of catfish farming in Mississippi ranks fourth behind poultry, forestry and cotton. The catfish industry in Mississippi is important nationally, accounting for 59% of the total national aquaculture output by weight and 65% by value. One of the most important water quality problems facing catfish producers is the development of off-flavors in fish, which refers to the presence of odorous metabolites in fish flesh that render the product unsuitable for marketing. The development of off-flavor is a severe economic burden for catfish farmers because it increases the length of time needed to raise a crop and interrupts the orderly flow of fish from the farm to the processor. Most flavor problems in pond-cultured catfish are caused by water-borne compounds that are synthesized by relatively few species of blue-green algae of known identities. As such, it may be possible to develop management strategies based on monitoring pond phytoplankton communities for the early development of problematic species. Control of algae-related off-flavors is difficult because it is not possible to predict the occurrence of flavor problems. Most current off-flavor management practices are reactive, and are implemented after fish have already developed flavor problems. Monitoring algal blooms for the presence of phytoplankton species that cause off-flavor can also improve decision making with respect to inventory management (i.e., harvesting), and, therefore, enhance cash flow. The ultimate goal of this research project is to provide catfish producers with a new tool for routine monitoring of ponds to detect phytoplankton that may cause off-flavor to cultured fish. If harmful species can be successfully discriminated with hyperspectral remote sensing, then catfish producers represent a potential market for remotely sensed images of production ponds.

The ultimate objective of this project is to determine whether reflectance data obtained by remote sensing can be used to monitor changes in the taxonomic composition of catfish pond phytoplankton communities. The goal is to develop a tool to detect low levels of odor-producing algal species to allow early intervention.

Specific objectives are to:

1. Develop unique pigment and radiance spectral profiles of pure cultures of phytoplankton species common to eutrophic catfish ponds.
2. Relate species biomass estimates, HPLC pigment profiles, and radiance spectral signatures to off-flavor metabolite production from single-species and mixed-species cultures of phytoplankton common in eutrophic, commercial catfish ponds.

Our general research approach will be to use a combination of microscopic examination of water, pigment, odorous metabolite and toxin analysis, and remote sensing as tools to discriminate phytoplankton species across multiple scales with progressively greater levels of system complexity. Studies will initially be conducted in simple systems consisting of laboratory cultures of phytoplankton. Direct microscopic examination of water will be used to determine wet biomass of phytoplankton. Pigment analysis will be used to develop unique spectral signatures for the phytoplankton species of interest. Hyperspectral radiometry will be used to detect and identify the presence of accessory pigments specific to groups of phytoplankton. Subsequently, the capacity of the technique to discriminate species within phytoplankton mixtures in cultures will be assessed.