Factors affecting faeces characteristics of yellowtail kingfish (Seriola lalandi).

During the past years, high value marine fish species gained importance in aquaculture. One of these marine fish species, which gained attention due to its rapid growth and high market price, is yellowtail kingfish (Seriola lalandi). However, farmed yellowtail kingfish have a significant higher eutrophication impact than other finfish species. This is related to its poor faecal quality, which is also characterized as “diarrhea-like” faeces by yellowtail kingfish farmers due to their instable consistency and fine faecal particles. This poor faecal quality makes it difficult to remove the faecal solids from the water, causing therefore high concentrations of total suspended solids (TSS) in the system and discharge water. For this reason, problems concerning animal health, system functioning, and environmental eutrophication occur. However, the TSS load in the system and discharge water is not only faecal quality dependent (water treatment efficiency), but also quantity dependent (e.g. digestibility of diets). Consequently, the overall project focusses on investigating factors affecting faeces quality and quantity of yellowtail kingfish. First, it is aimed to investigate the natural faeces consistency of yellowtail kingfish, to steer the later research. Thereafter, experiments will be performed to investigate the effect of different nutritional factors on faeces quality and quantity, including in depth research on the digestion kinetics of yellowtail kingfish. Lastly, it is aimed to validify these observations under semi- and full-practical conditions (‘Proof of principle’). Overall, this project should contribute to improve feed formulation for improving TSS management for yellowtail kingfish and may lead to practical tools to reduce TSS on farm level.