a b s t r a c tAntimicrobials, parasiticides, feed additives and probiotics are used in Asian aquaculture to improve the health status of the cultured organisms and to prevent or treat disease outbreaks. Detailed information on the use of such chemicals in Asian aquaculture is limited, but of crucial importance for the evaluation of their potential human health and environmental risks. This study reports the outcomes of a survey on the use of chemical and biological products in 252 grow-out aquaculture farms and 56 farm supply shops in four countries in Asia. The survey was conducted between 2011 and 2012, and included nine aquaculture farm groups: Penaeid shrimp farms in Bangladesh, China, Thailand and Vietnam; Macrobrachium prawn farms, and farms producing both Penaeid shrimps and Macrobrachium prawns in Bangladesh; tilapia farms in China and Thailand; and Pangasius catfish farms in Vietnam. Results were analysed with regard to the frequencies of use of active ingredients and chemical classes, reported dosages, and calculated applied mass relative to production. A range of farm management and farm characteristics were used as independent variables to explain observed chemical use patterns reported by farmers within each group. Sixty different veterinary medicinal ingredients were recorded (26 antibiotics, 19 disinfectants, and 15 parasiticides). The use of antibiotic treatments was found to be significantly higher in the Vietnamese Pangasius farms. However, total quantities of antibiotics, relative to production, applied by the Pangasius farmers were comparable or even lower than those reported for other animal production commodities. Semi-intensive and intensive shrimp farms in China, Thailand and Vietnam showed a decrease in the use of antibiotic treatments. These farm groups utilised the largest amount of chemicals relative to production, with feed additives and plant extracts, probiotics, and disinfectants, being the most used chemical classes, mainly for disease prevention. The surveyed farmers generally did not exceed recommended dosages of veterinary medicines, and nationally or internationally banned compounds were (with one exception) reported neither by the surveyed farmers, nor by the surveyed chemical sellers. Factors underlying the observed differences in chemical use patterns differed widely amongst farm groups, and geographical location was found to be the only factor influencing chemical ingredient application patterns in the majority of the studied farm groups.

Over the past few decades, Asian aquaculture production has intensified rapidly through the adoption of technological advances, and the use of a wide array of chemical and biological products to control sediment and water quality and to treat and prevent disease outbreaks. The use of chemicals in aquaculture farms has raised environmental concerns owing to their potential impacts on downstream aquatic ecosystems. Currently little is known about the environmental fate and effects of the chemicals used in Asian aquaculture. Consequently, we reviewed recent information on the use of chemical and biological products in the most important Asian aquaculture producing countries and briefly summarize their main potential environmental impacts. We provide an overview of the main factors controlling the use of these chemicals and describe the international risk assessment guidelines available for aquaculture chemicals. Finally, data gaps and research needs for their implementation in Asian countries are discussed. Our review aims to form a basis for developing environmental risk assessment studies of the chemicals used in Asian aquaculture

Background: Recently, increasing evidence supports that some complex diseases are not attributed to a given pathogen, but dysbiosis in the host intestinal microbiota (IM). The full intestinal ecosystem alterations, rather than a single pathogen, are associated with white feces syndrome (WFS), a globally severe non-infectious shrimp disease, while no experimental evidence to explore the causality. Herein, we conducted comprehensive metagenomic and metabolomic analysis, and intestinal microbiota transplantation (IMT) to investigate the causal relationship between IM dysbiosis and WFS. Results: Compared to the Control shrimp, we found dramatically decreased microbial richness and diversity in WFS shrimp. Ten genera, such as Vibrio, Candidatus Bacilloplasma, Photobacterium, and Aeromonas, were overrepresented in WFS, whereas 11 genera, including Shewanella, Chitinibacter, and Rhodobacter were enriched in control. The divergent changes in these populations might contribute the observation that a decline of pathways conferring lipoic acid metabolism and mineral absorption in WFS. Meanwhile, some sorts of metabolites, especially lipids and organic acids, were found to be related to the IM alteration in WFS. Integrated with multiomics and IMT, we demonstrated that significant alterations in the community composition, functional potentials, and metabolites of IM were closely linked to shrimp WFS. The distinguished metabolites which were attributed to the IM dysbiosis were validated by feed-supplementary challenge. Both homogenous selection and heterogeneous selection process were less pronounced in WFS microbial community assembly. Notably, IMT shrimp from WFS donors eventually developed WFS clinical signs, while the dysbiotic IM can be recharacterized in recipient shrimp.

We investigated aquaculture production of Asian tiger shrimp, whiteleg shrimp, giant river prawn, tilapia, and pangasius catfish in Bangladesh, China, Thailand, and Vietnam by using life cycle assessments (LCAs), with the purpose of evaluating the comparative eco-efficiency of producing different aquatic food products. Our starting hypothesis was that different production systems are associated with significantly different environmental impacts, as the production of these aquatic species differs in intensity and management practices. In order to test this hypothesis, we estimated each system's global warming, eutrophication, and freshwater ecotoxicity impacts. The contribution to these impacts and the overall dispersions relative to results were propagated by Monte Carlo simulations and dependent sampling. Paired testing showed significant (p < 0.05) differences between the median impacts of most production systems in the intraspecies comparisons, even after a Bonferroni correction. For the full distributions instead of only the median, only for Asian tiger shrimp did more than 95% of the propagated Monte Carlo results favor certain farming systems. The major environmental hot-spots driving the differences in environmental performance among systems were fishmeal from mixed fisheries for global warming, pond runoff and sediment discards for eutrophication, and agricultural pesticides, metals, benzalkonium chloride, and other chlorine-releasing compounds for freshwater ecotoxicity. The Asian aquaculture industry should therefore strive toward farming systems relying upon pelleted species-specific feeds, where the fishmeal inclusion is limited and sourced sustainably. Also, excessive nutrients should be recycled in integrated organic agriculture together with efficient aeration solutions powered by renewable energy sources.

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