Quantification of biofluorescence emitted by the Pacific whiteleg shrimp Litopenaeus vannamei during a stocking density trial

Welfare monitoring methods for the Pacific whiteleg shrimp Litopenaeus vannamei are currently limited to manual visual assessments. This widely cultured crustacean is increasingly reared under high stocking densities, and the development of non-invasive, automated monitoring tools is essential to improve welfare outcomes and farming performance. In this exploratory study, we recorded and quantified the fluorescent emissions of L. vannamei for the first time, investigating changes in biofluorescence in response to handling and a 3-h increased stocking density trial. Litopenaeus vannamei produces fluorescent emissions characterized by a broad green slope (∼ 500–560 nm) followed by a pronounced red secondary peak (∼ 700–730 nm). However, the intensity and anatomical areas of fluorescence were similar across triplicate experimental groups (n = 30) during pre-sampling, significant shifts were observed post-sampling. High individual variability was observed in the spectral data emitted from sampled haemolymph, with no clear relationship between external and haemolymph fluorescence at group level. This study suggests how to extract features from hyperspectral images that can be used for quantifying fluorescence emissions from L. vannamei, and the results presented here demonstrate the importance of proper handling of the shrimp to acquire useful data. The species is considered ideal for exploring digital optical monitoring of biofluorescence. Future research should establish baseline fluorescence profiles, which could serve as a non-invasive, real-time method to monitor health status and welfare in aquaculture operations.