Welfare Indicators for farmed rainbow trout: tools for assessing fish welfare

Abstract

Fish welfare is a key issue in commercial farming and is central to many decisions that farmers take during their daily husbandry practices and longer-term production planning. It is also a prominent topic for NGO’s, animal welfare organisations and charities, regulatory bodies, policy makers and consumers. Farmers have long been interested in optimising the welfare of their animals and actively employ strategies that address fish welfare concerns and attempt to minimise threats to fish welfare. Independent third-party organisations have even developed fish welfare standards and certification schemes for certain aquaculture species (e.g. RSPCA welfare standards for farmed Atlantic salmon and rainbow trout, RSPCA, 2018a, b). The topic of fish welfare has also been covered in numerous aquaculture research and review papers over the years, both from a fundamental and also applied perspective. This wealth of information and documentation can be spread over a wide range of sources that may not be easily accessible for the farmer and other end users. In many cases the wealth of information requires interpretation and representation before it is suitable for use out on the farm. Once the farmer has information on fish welfare, they need to implement it in their production systems and daily husbandry practices. This can be a serious challenge as even measuring fish welfare can be challenging and the tools available for measurement may not be suitable for all species or all life stages. To assess the overall welfare status of the fish we use Welfare Indicators (WIs). Welfare indicators can either be direct animal-based (something you get from the fish), or indirect resource-based (e.g. rearing environment, infrastructure etc.). However, some WIs may be too complex or too difficult to apply on a farm. WIs that are appropriate for on-farm use are termed Operational Welfare Indicators (OWIs). WIs that can be sampled on the farms but need to be sent to a laboratory or other remote analytical facility are termed Laboratory-based Welfare Indicators (LABWIs). There are other potential WIs that cannot currently be classified as either OWIs or LABWIs, these are mainly used in research but may be useful in the future or under specific circumstances at present. From the suite of appropriate OWIs or LABWIs available, the end user then needs to apply these to different production systems and husbandry routines. This is the goal of this handbook – to assemble a farm-friendly toolbox of fit for purpose Operational Welfare Indicators (OWIs) and Laboratorybased Welfare Indicators (LABWIs) for use out on fish farms in different production systems and husbandry routines. It also includes advice on their implementation and interpretation. The FISHWELL welfare indicator handbook for rainbow trout is an output of the Norwegian Seafood Research Fund (Fiskeri- og havbruksnæringens forskningsfinansiering, FHF) project «FISHWELL: Kunnskapssammenstilling om fiskevelferd for laks og regnbueørret i oppdrett». It utilizes the text and format of the earlier FISHWELL salmon handbook (Noble et al., 2018) as a basis for this work, updating the data and contents with literature based upon rainbow trout. The project group included a diverse range of welfare scientists and veterinarians from Nofima, the Institute of Marine Research, Nord University, the Norwegian Veterinary Institute (all Norway) and the University of Stirling (UK). For a list of authors see each specific section of the handbook.