The aquaculture industry is becoming increasingly aware of the importance of water chemistry on production and organism welfare when considering environmental change and technologies such as Recirculating Aquaculture Systems (RAS). Reduced growth, feed conversion ratio, and condition factor as well as increased bone remodelling, incidence of cataracts and kidney stone formation has been observed in fish exposed to elevated CO2 synonymous with RAS . However, such impacts are not always observed suggesting that the interaction of CO2 with other water chemistry variables is not fully understood regarding organism physiology.
Key factors which determine water chemistry include the local geology impacting the source water (Fig. 1) , farm water management strategies (e.g. oxygenation, CO2 stripping, addition of alkali, biofiltration) and system design ( e.g. flow through tanks , RAS, sea cages) . In the UK, the range of water chemistries experienced by rainbow trout is currently unknown. My research aims to create the first overview of trout farm water chemistry in the UK and determine any links with fish physiology, health, production etc . This has been determined by farmer su rveys and collecting water samples from farm sites to measure oxygen, temperature, salinity, CO2, total alkalinity, sodium, potassium, magnesium, calcium, chloride, nitrate, phosphate, and sulphate. Furthermore, information was gathered on local geology, farm management strategy, system design and common health problems. Data were analysed to determine which factors contribute the most to farm water chemistry and whether there were any relationships between water quality , intensity of production and fish health. There is also further scope for sampling outside of the UK, including Denmark (Fig. 1).