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The concept of "biofloc technology" is changing the facet of intensive aquaculture with scope to attain high productivity in a sustainable manner. In biofloc, dense heterotrophic bacterial community is developed through C:N ratio manipulation, where the system becomes bacterial dominated rather than algae dominated and takes care of the wastes generated through in situ bioremediation. Protein is utilised in two ways; as feed for the shrimp and as microbial floc when the heterotrophic microbes convert the nitrogenous wastes into protein. It also promises a healthy rearing system, which is increasingly identified as one possible solution for disease problems especially those striking at early stages. The purpose of this study was to evaluate the effect of biofloc and periphyton technology (BPT) on the growth and immunomodulatory performance of Pacific white shrimp Penaeus vannamei during nursery and grow-out culture. The experimental BPT treatments with three tier substrate system with molasses as carbohydrate (CHO) source were compared with the conventional autotrophic system. The immunomodulation and cumulative percentage mortality upon challenge with pathogenic strain of Vibrio parahaemolyticus were assessed in the reared animals. We have successfully demonstrated the BPT based nursery and growout systems for P. vannamei with the advantage of providing significantly (p<0.05) better growth (27.6% improvement in average body weight, ABW) and feed utilisation (31% improvement in feed conversion ratio, FCR). A production level of 4-4.5 kg m -3 of water was achieved through this BPT system registering a significant improvement over the conventional system (p<0.05). The cumulative percentage mortality following pathogen challenge was significantly lower (p<0.05) in the biofloc grown shrimps compared to that of the control group, thus showing better resistance to pathogenic challenge. Furthermore, the biofloc reared shrimp did exhibit significant improvement in non-specific immune response in terms of serum phenoloxidase activity and total haemocyte counts possibly suggesting potential immunostimulatory role of the biofloc associated heterotrophic bacteria. This eco-based technology as revealed through our studies brings substantial improvement in productivity, minimising water requirement, recycling in situ nutrients and organic matter in turn improving farm biosecurity, augmentation of natural food, improvement of FCR and better health of the cultured shrimp.

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Shrimp aquaculture in India is synonymous with coastal aquaculture. Like other agricultural activities, it appropriates a wide range of environmental goods and services, and is vulnerable to impacts of climate change as the cultured animals are sensitive to various kinds of biotic and abiotic stressors. Climate change affects the shrimp aquaculture directly by extreme weather events and seasonal variations, and indirectly alter the primary and secondary productivity, structure and composition of the ecosystems or by influencing the availability of fishmeal, fish oil and other goods and services required for aquaculture farmers. The perceptions of farmers on the impacts of climate change on shrimp aquaculture in inland and coastal areas of Krishna District, Andhra Pradesh are discussed. Cyclone and flood were perceived by all the farmers, whereas irregular season, high temperature, heavy rain and drought were perceived by 79, 89, 91 and 5 % of farmers, respectively. Environmental, biological, and economic impacts of climate change drivers on aquaculture indicated 20 to 30 % loss due to seasonal variations and 50 to 100% loss due to extremely heavy rainfall, flood and cyclones. The economic risk rating was high with flood followed by the cyclone and the magnitude was more in coastal areas compared to inland areas. There is no universally applicable list of adaptation measures and need to be evaluated for individual aquaculture systems. Autonomous and planned adaptation measures to be implemented by farmers, researchers and policymakers are discussed for climate-resilient aquaculture. Planned adaptive measures are either at the primary level or non-existence, hence policy initiatives are required to formulate planned adaptive measures to enhance the adaptive capacity of the farmers.