Kathleen Mae Trebol’s scientific contributions

The majority of shrimp producers utilize probiotics derived from terrestrial sources as part of their aquaculture management. The beneficial effects of terrestrial probiotics on shrimp may be affected due to environmental differences between the cultivated species and the source of the probiotics. To ensure maximum effects on the host, it is essential to use probionts derived from the host or the environment of the cultured organism. Consequently, the objective of this study was to isolate and characterize potential probionts from brackishwater by enriching the water with organic sources containing a high ratio of carbon to nitrogen (C:N). Six 10-li containers were filled with brackishwater from an estuary for a mesocosm experiment. To stimulate bacterial growth, water was enriched with either molasses or brown sugar at a C:N ratio of 15. After twenty days, all heterotrophic bacteria in the enriched water were enumerated. The in vitro antagonistic activities of distinct bacterial colonies against Vibrio harveyi, a crustacean pathogen, were evaluated on fresh Nutrient Agar plates containing 1% sodium chloride. There were 10 bacterial isolates with in vitro antibacterial activity. These bacterial isolates are categorized as belonging to the putative genera Acinetobacter, Pseudomonas, Sphingobium, and Rheinheimera. The implications of this study suggest that enriching brackishwater with organic carbon sources at high C:N ratios may increase the likelihood of isolating and developing potential probionts for shrimp aquaculture.

Nursery production of shrimp is usually done in small ponds; however, the use of small and circular tanks with plastic liners is gaining popularity. From an industry standpoint, there is still a need to assess how nursery systems can be of benefit to the shrimp production cycle. Hence, the use of small circular tanks coupled with the incorporation of biofloc technology was assessed in terms of its viability during the nursery production of the Pacific whiteleg shrimp, Penaeus vannamei. A 450m 2 plastic lined circular tank was installed and prepared for the stocking of P. vannamei postlarvae (PLs) at a density of 500 PLs per m 2. Biofloc was produced and maintained throughout the nursery phase using brown sugar as carbon source at a carbon to nitrogen (C:N) ratio of 10. Water quality was monitored daily, while presumptive Vibrios were enumerated weekly. Sampling for growth was done at the 14 th day post-stocking and weekly until harvest on the 30th day. The different water quality parameters were within optimum levels required for shrimp growth. Presumptive Vibrios were dominated by the yellow colonies. At the end of the nursery phase, there was 100% survival and the shrimp attained an average body weight of 1.26 g and a feed conversion ratio (FCR) of 0.43. Our results indicate that the use of small circular tanks with biofloc during the nursery production phase of whiteleg shrimp is feasible and can be incorporated in the grow-out culture of this shrimp species.

The increasing global population resulted in intense pressure on the food production sectors to meet the rise in food demand. The aquaculture industry, which is one of the major food production sectors, provides opportunities in addressing issues on malnutrition and poverty alleviation. Shrimp farming is an important sub-sector in aquaculture because shrimp are not only good sources of food, but they contribute to the national economy through export revenues. This resulted in the rapid intensification of shrimp aquaculture, which created negative issues on sustainability and environmental impacts. Hence, this necessitates an urgent need to develop aquaculture production systems that yield high productivity and profitability yet possess a low carbon footprint. Biofloc technology (BFT) fit into these criteria as this technology permits intensive culture of aquatic species, less use of resources, and improved water quality as a consequence of the production and activity of beneficial microbial biomass, which, at the same time, can be utilized as a source of feed for the growing shrimp. BFT has been shown to be successful on a commercial scale during shrimp grow-out, and recent studies have shown that this technology can be further refined and optimized for the production of shrimp during the nursery phase. This review, therefore, highlights the basics of BFT and how this technology is being optimized in the production of shrimp during the nursery phase. More specifically, this discusses the benefits of this approach in ensuring a productive yet sustainable way of producing shrimp in the context of Philippine aquaculture.