The growing interest in sustainable aquaculture has driven the development of technologies like Recirculating Aquaculture Systems (RAS), which optimize production and reduce environmental impact. To effectively transfer knowledge to students and producers, state-of-the-art facilities are crucial. In this context, the University of Hawaiʻi at Mānoa has developed the Tuahine Aquaculture Research and Education Center (TAREC), a facility designed to integrate research, education, and outreach.
An initial study was conducted to validate the capabilities of this new facility by comparing the growth of Mozambique tilapia (Oreochromis mossambicus), a species of significant commercial interest, in freshwater (FW) and artificial seawater (ASW) RAS. The results not only confirm TAREC’s versatility but also provide valuable data on the performance of this species at different salinities.
Key findings
- A novel aquaculture center (TAREC) was built at the University of Hawaiʻi, designed with two RAS to operate simultaneously with freshwater and seawater.
- The first trial evaluated the growth of Mozambique tilapia (Oreochromis mossambicus) in freshwater (FW) versus artificial seawater (ASW) over three months.
- Fish farmed in artificial seawater (ASW) showed a significantly higher specific growth rate (SGR) and final weight than those in freshwater.
- Feed efficiency was superior in the saltwater group, with an overall feed conversion ratio (FCR) of 0.84, compared to 1.04 in the freshwater group.
- The study successfully validates the TAREC center’s capability as a versatile facility for applied research, education, and training in aquaculture.
A cutting-edge center for future aquaculture
TAREC is a compact and adaptable facility housing two main RAS, designated R1 (designed for saltwater) and R2 (for freshwater). This dual configuration allows for the simultaneous cultivation of freshwater and marine organisms, as well as experiments with salinity gradients.
The center’s design prioritizes efficiency and sustainability. Water from the culture tanks flows by gravity to filtration systems for solids removal (swirl filters and fixed-bed filters) before passing to a moving bed bioreactor (MBBR) for biofiltration. Finally, a single variable-speed pump per system returns the treated water to the tanks, minimizing energy consumption.
This infrastructure directly supports Hawaiʻi’s strategic priorities by enabling research in:
- Diversification of marine and freshwater species.
- Improved cultivation of key species for local food security, such as tilapia.
- Development of Integrated Multi-Trophic Aquaculture (IMTA) and aquaponics.
- Practical training for students and future industry professionals.
The Experiment: Mozambique Tilapia Put to the Test
To evaluate and validate the operation of TAREC’s RAS, researchers conducted a three-month growth trial with Mozambique tilapia.
- Experimental Design: Ten tanks were used—five connected to the freshwater system (R2) and five to the artificial seawater system (R1).
- Population: Each tank was stocked with 25 tilapia with an initial average weight of approximately 13 grams, reaching an initial biomass of 0.6 kg/m³.
- Acclimation and Conditions: The fish in the saltwater group were gradually acclimated to a salinity of 33‰. Water temperature was maintained between 26-30°C in both systems.
- Feeding and Measurements: Fish were fed once daily ad libitum. Body weight, total length, and feed consumption were measured weekly to calculate the specific growth rate (SGR) and feed conversion ratio (FCR). Water quality, including total ammonia nitrogen (TAN) and nitrite-nitrate, was continuously monitored.
Salinity Makes the Difference
The study demonstrated clear advantages in the performance of tilapia raised in artificial seawater compared to freshwater.
Stay Always Informed
Join our communities to instantly receive the most important news, reports, and analysis from the aquaculture industry.
Superior Growth in Saltwater
At the end of the 13-week trial, fish in the ASW system reached a significantly higher body weight than those in the FW system. Weight differences became statistically significant from week 5 onward, while differences in length were observed as early as week 3. The overall specific growth rate (SGR) was notably higher in the ASW group (1.50) compared to the FW group (1.30).
Better Feed Efficiency
One of the most relevant findings was the difference in feed efficiency. Although the total amount of feed supplied to both groups was not significantly different, the fish in ASW converted that feed into biomass much more efficiently.
The overall FCR was significantly lower for tilapia in ASW, with a value of 0.84, compared to the 1.04 FCR recorded in the FW group. This indicates that less feed was required to produce the same amount of fish in the saline environment.
Water Quality and System Performance
Water quality parameters remained within optimal levels for tilapia farming throughout the experiment. Concentrations of total ammonia nitrogen (TAN), nitrites, and nitrates were kept well below the toxic thresholds reported for the species (less than 0.35 ppm for TAN and 22 ppm for nitrite-nitrate). This confirms that TAREC’s biofiltration systems performed effectively even as biomass increased.
Conclusions and Implications for Tilapia Farming
This first trial at the TAREC facility has not only successfully validated the design and operation of its dual RAS but has also reinforced knowledge about the physiology of Mozambique tilapia. The results corroborate previous studies conducted in flow-through systems: this euryhaline species grows faster and more efficiently in saltwater environments.
For aquaculture producers, this underscores the potential of farming tilapia in indoor RAS using saltwater, which could improve profitability by reducing the FCR. Furthermore, TAREC’s capacity to host applied research, train the next generation of professionals, and collaborate with the industry positions it as a key hub for advancing sustainable aquaculture in Hawaiʻi and the Pacific region.
Contact
Andre P. Seale
Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resilience, University of Hawai‘i at Mānoa,
1955 East-West Road, Honolulu, HI 96822, USA
E-mail: seale@hawaii.edu
Reference (open access)
Seale AP, Fox BK, Celino-Brady FT, et al. Evaluation of a novel recirculating aquaculture center for research, education, and extension at the University of Hawai’i at Mānoa. Israeli Journal of Aquaculture – Bamidgeh. 2025;77(3):56-67. doi:10.46989/001c.142156
Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.
