Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio

Dynamic nuclear polarization with nitroxides dissolved in biological fluids.

The most widely used free radicals for dynamic nuclear polarization (DNP) experiments or related Overhauser imaging are nitroxides. The DNP parameters in biological fluids were measured in order to provide guidelines for the design of new nitroxides, adapted to the biological applications of DNP. Eighteen nitroxides were studied at a concentration of 1 mM. Extrapolation at complete electron paramagnetic resonance saturation and proton longitudinal-relaxation-time measurements enable calculation of the coupling factor between nitroxide free electrons and water protons. In deoxygenated phosphate-buffered solutions, the NMR signal enhancement by DNP ranged from -36.3 to -6.7, and the coupling factor ranged from 0.31 to 0.03. Nitroxides with a long side chain yield poor enhancement, although their relaxivity is far greater than that of nitroxides with small chains. In a 1 mM albumin solution, the loss in enhancement factor is mainly caused by the fact that proton relaxation occurs via interactions, not only with the dissolved free radicals but also with the albumin macromolecules. In serum, the enhancement factor is lower than that in an albumin solution, because of the higher protein concentration in serum. In red-blood-cell suspensions, the enhancement factor was further decreased. Two effects contribute to this decrease: first, the increased viscosity due to the presence of red blood cells, and second, the susceptibility effects of the paramagnetism of deoxyhemoglobin. The high sensitivity to oxygen of DNP in phosphate-buffered solution is also greatly reduced when nitroxides are dissolved in blood.(ABSTRACT TRUNCATED AT 250 WORDS