Assessing feed attractability in Pacific white shrimp (Litopenaeus vannamei) using an automated tracking software

Abstract

In shrimp farming, there has been a considerable focus on the development of novel additives that might reduce costs associated with the time taken by shrimp to locate and ingest feed. However, within these trials there has been little consideration of the role that feeding behaviour of individuals can play in assessing the attractability of additives. As such, the use of tracking technologies in the development of automated protocols is beginning to gain attention as an important tool for monitoring associated behaviours. Therefore the objective of the present study was to validate an automated tracking software (EthoVision) for assessing feed attractability in Pacific white shrimp (Litopenaeus vannamei). Twenty-seven juvenile shrimp (5.54 ± 1.37 g) were used to test three experimental diets with different theoretical levels of attraction; negative (0.07 M quinine-HCl), control, and positive diet (3% attractant). Shrimp were individually video recorded in test arenas for 20 min with each one of the diets. Recordings were also carried out at two times of day (morning and afternoon) to evaluate the effect of time of day on shrimp feeding behaviour. The behaviour of each individual was recorded three times per diet to determine levels of individual variation. Comparison between manual and automated observations validated the reliability of EthoVision in analysing L. vannamei feeding behaviour and the software detected clear differences in feeding behaviour according to diet. Shrimp provided with the positive diet (i.e. 3% attractant) arrived faster and spent longer on the feeding area. In contrast, with the negative diet (i.e. 0.07 M quinine-HCl), shrimp spent more time moving around the test arena and less time interacting with the feed. Time of day also had an effect on several behaviours, but not on the time spent on the feeding tray. Less individual variation in feeding behaviours was found when shrimp were fed the positive diet, suggesting attractive diets can decrease variability in feeding behaviour with potential applications to commercial ponds. Distribution heatmaps provided by EthoVision offered a quick and reliable assessment of feed attractability. The results of this study highlight the use of tracking technologies to assess feed attractability in L. vannamei and the feasibility of automated protocols for the industry.