Introduction
Over 400 billion shrimps are farmed each year worldwide, more than five times the total number of all farmed land animals. Despite these facts, our scientific knowledge on shrimp behaviour and welfare is quite weak.
This study focuses on the feeding behaviour of Penaeus vannamei . According to the literature, shrimp feed in small quantities; offering feed increases exploration, crawling and feed grabbing; while f eed-deprivation and molt status influence the feeding behaviour . Nevertheless, there are controversial studies regarding the preferred feeding time by shrimps and the best feeding frequency. Moreover, the way shrimp behave in groups during feed distribution is still unknown.
Material and methods
The study aimed to observe shrimp behaviour directly in raceways in commercial farms, with one raceway being fed every hour during daytime (from 7 am to 7 pm) and the other being fed every hour during day and night, with the same feed quantity per 24h in both raceways. The behaviour of shrimp has been recorded every three days, four times a day, for 15 minutes around feeding time via GoPro. These videos have been analyzed based on an ethogram designed for this study . Water quality has been recorded several times a day and 60 shrimp have been sampled every day to score eight health indicators to see how shrimp react to different feeding schedules. To estimate shrimp activity levels, we performed image scans every 30 seconds over the course of 15-minute video recordings. At each scan (i.e., video still frame), we counted the number of shrimps that were resting on the substrate versus those that were suspended in the water column. This snapshot-based approach allowed us to quantify temporal patterns of activity based on spatial positioning. Furthermore, weight has been recorded every two days based on a shrimp sample leading to a weight mean.
Results
One of the main concerns of farmers was the water quality and the possible deterioration in case of frequent feeding. The results showed no difference in the two raceways which is good news for producers. Furthermore, c oncerning weight, shrimp fed day and night gain more weight than those fed only during the day .
The scan sampling based on videos r evealed that shrimp fed only during the day were significantly more active—i.e., more frequently observed in suspension—during the feeding compared to shrimps fed day and night . This higher activity for shrimps fed during the day only was also observed before the first feeding of the day (7 am) suggesting an anticipatory response to food availability.. To conclude, feeding the shrimp every hour during night and day lead to have behaviours closer to natural shrimp behaviours which tend to rest more on the substrate.
Conclusion
It is a pioneer study as it has never been done to observe and analyze shrimp behaviour in commercial farms without using AI. A better understanding of shrimp feeding behaviour will help many farmers and also improve the lives of many shrimps in commercial farms.
More similar studies would be a key to confirm the different results, especially concerning the weight to ensure that all shrimps gain more weight.