EXTRACELLULAR POLYSACCHARIDES (EPS) IN AQUACULTURE AND THEIR IMPORTANCE IN HATCHERIES, BIOFLOC AND BIOFILTERS
Extracellular Polymeric Substances (EPS), or exopolymers have received limited attention in aquaculture, despite their influence on all aspects of production systems from hatcheries to biofloc production. EPS serve an important role in nutrition both directly through particle selection for instance by filter or detrital feeders, and indirectly, through their contribution to microflora in the larval gut of both fish and invertebrates. EPS are also integral to biofloc production and are well understood for their roles in the biofilters of recirculating aquaculture systems. Hatcheries have long dealt with EPS in microalgal cultures or larval rearing systems when quantities manifest themselves visually as biofilms or mucilaginous aggregates.
Despite this, they have received limited attention for their roles in hatcheries, perhaps on account of their invisibility using normal microscopy and extremely small size, both factors which may explain why they are sometimes also referred to as transparent exopolymeric substances (TEPs). In this presentation, we will provide an overview of EPS in aquaculture, with a particular emphasis on their role in hatchery biofilms and 'green water' (or microalgal) production, and we will provide preliminary results from experiments testing the roles of extracellular polysaccharides on feed quality.
Our results suggest that EPS production has important implications for micronutrient bioavailability and bacterial loading in hatcheries that produce crustaceans, shellfish as well as systems for production of rotifers and Artemia that are used as live fish-feeds. The reliability of hatchery production and quality of feed could be improved by taking EPS characteristics and quantities into account. We suggest that development of sensors capable of monitoring EPS production is feasible and potentially a cost-saving measure that could enhance the quality of feed for cultured organisms.