The Benefish consortium reports on the influence of system water refreshment rates on realized feed load, weight development, fish physiology and behaviour in turbot

Farmers with recirculation aquaculture systems (RAS) have a greater necessity and capacity to control the culture conditions of their farms than farmers with other aquaculture systems. Water quality is one of the factors that is closely monitored and managed in order to maintain the optimal levels of oxygen, ammonia, temperature, pH, and CO2. Effects of these parameters on growth and health are well studied and almost immediately noticeable. In RAS it often occurs that, although water quality conditions seem to be optimal, the feed intake of the fish might suddenly diminishes, thus reflecting a situation of sub optimal welfare of the animals. This phenomenon is particular relevant in marine RAS where these situations of reduced feed intake occur even though the normally monitored water quality parameters and husbandry conditions appear to be optimal. Similar phenomena also occur in other aquaculture culture systems, such as flow through systems, where feed intake fluctuates whilst the reasons are not always known, although there is typically less control and monitoring compared with RAS. It is therefore necessary to actively monitor deviation of expected feed intake, in combination with the monitoring of culture conditions and farm management on pilot-scale level. Only through this intermediate level experimental work and farm observations for the assumed relationship between deviation of expected feed intake and fish welfare can be validated. It is furthermore necessary to provide refinements to causative relationships expected to be found on commercial farms, where it is often claimed that e.g. lower system water refreshment rates or more closed RAS are leading to growth retardation and lower feed intake in fish and thus lower production. The present study is, therefore, intending to prove the hypothesis that changes in feed intake can be associated with changed fish welfare status, using turbot as model species. It is furthermore hypothesized that this changed fish welfare status is caused by different system water refreshment rates and fish and system management. As a final result, feed intake should relate by same efficiency to lower fish growth in closed RAS compared to flow through systems. The objectives are therefore to validate the relationships between deviation from expected feed intake and fish welfare, and their causative factors on the commercial farms interpreting data on feed intake, behavior, endocrinology and immune patterns as welfare indicators

Aquaculture system diversity and sustainable development : fish farms and their representation

Initiatives for the sustainable development of aquaculture have so far focused on the production of codes of conduct, of best management practices, of standards etc., most of which have been developed by international organisations, the industrial sector and non governmental organisations. They were, to a large extent, produced using a "top down" process and inspired by models from intensive industrial shrimp and sea fish farming (mainly salmon). However, most of global aquaculture production comes from small-and medium-sized farms, essentially in Asia which contributes 92% of the total world aquaculture production volume. The objective of this article is to define the contours of systemic typologies that are able to express the sustainability conditions of aquaculture systems. The proposed approach builds on surveys of aquaculture systems which differ in terms of their biogeographical nature (temperate/tropical and north/south countries) or their farming techniques and their governance systems. This work is a prerequisite to any attempt at an individualised and comparative evaluation of specific aquaculture systems from either global or territorial viewpoints. In order to go beyond the cleavage of a typology based on the differentiation between developed and developing countries, three typologies were produced. These typologies allow for discriminatory variables to be identified such as for example the marketing methods or the pace of innovation: a structural typology, a functional typology and a systemic typology. Finally, the representations of aquaculture activity and of its sustainability that producers have of the 4 different types that emerge from the systemic typology were recorded and analyzed

Three systems of rail tourism: the example of French railways

International audienc

Water delivery capacity of a vacuum airlift : Application to water recycling in aquaculture systems

International audienc

Mass transfer efficiency of a vacuum airlift-application to water recycling in aquaculture systems

International audienc