Introduction
The iFishIENCi project aims to demonstrate the viability of sustainable feeds that support the development of new production species with improved growth and feed utilization efficiencies. This involves the implementation of effective monitoring systems for fish health and welfare, as well as the adoption of efficient feeding practices that reduce the pressure on sources of fish-feed ingredients such as agricultural crops and wild-caught fish for fishmeal and oil. The project targeted several species, including Asian seabass (Lates calcarifer), rainbow trout (Onchorynchus mykiss), and catfish (Clarias spp.), and employed a multidisciplinary and holistic approach at AquaBioTech group to develop feed and feeding technology in RAS.
Experiment 1
The Asian seabass, Lates calcarifer, is a popular farmed species with an established market, and its potential for expansion of barramundi farming worldwide has been noted (Lawley, 2010). However, the cultivation of this fish in a recirculating aquaculture system (RAS) needs further development (Larkin, 2000). The trial performed within the project compared the growth and body quality traits of Asian seabass reared at two different salinity levels in RAS, and tested the potential benefits of a microalgae extract (Nannochloropsis gaditana) for fish growth, health, and fillet traits. The study found no significant differences in weight, specific growth rate, and most body quality traits between the different treatments, but fish in higher salinity (S1) had a significantly higher visceral-somatic index (VSI) compared to those in lower salinity (S2). The microalgae extract did not have a significant effect on the growth, health, or fillet traits of the fish. These findings suggest that further research is needed to optimize the RAS culture of Asian seabass and to determine the potential benefits of microalgae extracts in improving fish growth and health.
Experiment 2
Catfish is one of the fastest-growing sectors in the aquaculture industry, and its production has increased significantly over the past few years (FAO 2020). Clarias is one of the most popular types of catfish, and its hybridization has been studied to improve growth and disease resistance (Rahman et al., 2018). Sustainable aquaculture production is crucial, and aquaculture sustainability requires reducing dependence on traditional raw materials (Shah et al., 2018). The experiment compared the growth performance, morphometric indexes and body colour intensity of hybrid catfish (Clarias gariepinus ♀ x Heterobranchus longifilis ♂) fed with a control diet consisting primarily of land-based and animal-based ingredients with two experimental diets containing Candida utilis at 10% and 20% inclusion levels. The results showed no significant difference in growth performance among the treatments. The bio-morphometric indexes also showed no significant difference. However, the red/green coordinate in the body colour intensity of the 20% inclusion diet was significantly higher than the control diet. The inclusion of C. utilis reduced the plant-based ingredients in the diets by about 14% and 28% but did not affect growth performance. The study demonstrates the potential of C. utilis as a novel and sustainable alternative protein source for the aquafeed industry. Although the results are promising, further investigation is required to evaluate the interaction among the ingredients in formulated diets and the relative effect on digestibility and gut impact in hybrid catfish. The study suggests that catfish farming is a valuable candidate for further investigation due to its growing interest worldwide and the development of related technology.
Experiment 3
To ensure economic benefits and efficient growth in aquaculture, appropriate feeding management is crucial. Inadequate feeding strategies can lead to low growth and feed conversion efficiency, resulting in increased labour costs (Wu et al., 2004). Temperature is also a crucial factor affecting fish growth and survival, as it affects physiological and biochemical functions. The gastric evacuation rate (GER) in fish is a significant factor affecting feed intake and digestion and it can be estimated through the serial retrieval of gastric contents, and the optimal feeding frequency is closely related to GER conditions (Seymour, 1989). Overfeeding can lead to negative consequences such as gastrointestinal overload and reduced food utilization efficiency (Jobling, 1986).
This study aimed to determine the optimal feeding strategies for rainbow trout (Onchorynchus mykiss) at different temperatures (16±1°C, 18±1°C, and 20±1°C) by conducting a gut transit study after starvation for various time frames. The digestive tract of the sampled fish was divided into three parts (stomach; anterior + mid intestine, and posterior intestine), and the collected gastric content was weighed and stored separately. The wet and dry weights obtained after drying the samples at 60°C for 24 hours were used to calibrate a digital twin model (FishMet) for rainbow trout under different temperature. The results will be presented as part of the project implementation.
References
Food and Agriculture Organization of the United Nations (2020). Global Forest Resources Assessment 2020 (FRA 2020), Food and Agriculture Organization of the United Nations, Food and Agriculture Organization of the United Nations, Rome(URL: https://doi.org/10.4060/ca9825en).
Jobling, M. (1986). Gastrointestinal overload—a problem with formulated feeds?. Aquaculture, 51(3-4), 257-263.
Larkin, B. (2000). Recirculating aquaculture systems in Australia: a synthesis of systems, species and the networking approach. In Proceedings of the 3rd International Conference on Recirculating Aquaculture, Roanoke, VA (USA) 20-23 Jul 2000.
Lawley, D. B. (2010). Repositioning Australian farmed barramundi: Online consumer survey findings. University of Sunshine Coast, Sunshine Coast, QLd.
Rahman, M. A., Lee, S. G., Yusoff, F. M., & Rafiquzzaman, S. M. (2018). Hybridization and its application in aquaculture. Sex control in aquaculture, 163-178.
Seymour, E. A. (1989). Devising optimum feeding regimes and temperatures for the warmwater culture of eel, Anguilla anguilla L. Aquaculture Research, 20(3), 311-324.
Shah, M. R., Lutzu, G. A., Alam, A., Sarker, P., Kabir Chowdhury, M. A., Parsaeimehr, A., ... & Daroch, M. (2018). Microalgae in aquafeeds for a sustainable aquaculture industry. Journal of applied phycology, 30, 197-213.
Wu, G., Saoud, I. P., Miller, C., & Davis, D. A. (2004). The effect of feeding regimen on mixed-size pond-grown channel catfish, Ictalurus punctatus. Journal of Applied Aquaculture, 15(3-4), 115-125.
Acknowledgement
This research was conducted under the iFishIENCi H2020 project. The iFishIENCi project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 818036.