Finfish marine aquaculture in Northern Vietnam: Factors related to pathogen introduction and spread

Abstract Marine finfish aquaculture is a rapidly growing subsector in the Asia-Pacific region, including Vietnam. However, in-depth information about health management practices is often inadequate. Our objective was to describe multi-species marine finfish aquaculture in northern Vietnam at the farm and species level, and identify practices that may influence fish health. Two surveys were conducted in April 2014 and April 2015 on respectively 120 and 119 farms of which 57% were the same farms, located in floating villages near Cat Ba Island in Hai Phong Province, Vietnam. Most management practices were not different between the multiple species per farm. Duration of grow-out season was part of both surveys and differed for most species between surveys, and also with findings from other studies. Most farmers did not have aquaculture related education. Few farmers recorded stocking, harvesting or mortality parameters, and there was little involvement of health professionals. Most stock originated from China, which could pose a risk on emerging diseases. Median proximity of farms was 3 m, which is a large potential for spread of pathogens between farms. There were few biosecurity practices in place to prevent pathogens from entering the farm, e.g. few farmers treated fish before stocking, and none indicated disinfection of harvesters. Overall mortality was different between species, but overall 50–75% was expected for many production cycles. This study provides a basic understanding that could inform future outbreak investigations or development of risk-based surveillance programs. Statement of relevance This is the first study that provides a basic understanding of health related factors in marine finfish aquaculture management in northern Vietnam. As the sector is growing, early interventions to adapt farmers to better practices may lead to a cascade of improvements, and may optimize and stabilize the sector as more families become dependent upon the industry for their livelihoods.