Recirculating aquaculture systems (RAS) are intensive systems where water is reused through mechanical and biological treatment to reduce water consumption and maintain good quality. Adequate water quality is essential to ensure the growth and survival of aquaculture species reared in RAS.
Traditionally, water quality parameters have been measured at specific intervals using manual sensors and laboratory analysis, requiring trained technical personnel.
Currently, a variety of sensors and monitoring equipment are available for real-time monitoring of water quality parameters. However, these modern systems require competent users and regular maintenance and calibration.
Researcher Petra Lindholm-Lehto from the Natural Resources Institute Finland (Luke) published a scientific review summarizing water quality parameters, sensor variety, and monitoring technologies to provide an overview of current water quality monitoring systems.
Water Quality Parameters
In the aquaculture industry, various parameters need to be monitored and measured to understand water body conditions. These include pH, temperature, dissolved oxygen, salinity, and turbidity.
Fluctuations in water quality parameters directly affect the health, growth, and feeding utilization of reared species. For instance, dissolved oxygen affects feed consumption, feeding efficiency, metabolism, and fish growth.
Temperature fluctuations impact feed utilization and induce stress that can lead to disease outbreaks. Similarly, pH can be influenced by bacteria, CO2 content, and chemicals in the system. Low water pH can be hazardous for aquatic species.
Water Quality Measurements
Successful intensive aquaculture requires monitoring various water quality parameters. In recent years, instrumentation, automation, and monitoring systems have been developed, becoming common for measuring basic parameters.
The development of information technology and low-cost sensors has increased the feasibility of monitoring through wireless sensor networks (WSN).
Efficient real-time water quality monitoring is essential to ensure cost-effective RAS management. The aquaculture industry is trending towards automatic remote monitoring and computerized control systems.
Water quality monitoring should encompass multiple parameters. Some require constant monitoring (e.g., dissolved oxygen, CO2, pH) to prevent detrimental RAS disruptions, while others can be monitored less frequently (e.g., off-flavors, trace elements, metals).
However, effective online monitoring systems are not available for all parameters, especially at a reasonable cost.
Several methods for water quality monitoring have been reported. Typically, they measure basic water quality factors (e.g., DO, pH, temperature) significantly affecting reared species’ survival.
Recent years have seen a variety of monitoring systems, such as a remote monitoring system for aquaculture, achieving long transmission distances, rapid communication, and high-quality transmission with 4G technology. In the future, 5G technology will further enhance data transfer.
Internet of Things (IoT) in Aquaculture
In recent years, the Internet of Things (IoT) has become common. In aquaculture, IoT has been applied to real-time water level and pumping adjustment monitoring.
IoT systems in the aquaculture industry typically employ WSNs with broad coverage and scalability. These technologies include Zigbee, Bluetooth, and General Packet Radio Services (GPRS)/CDMA/long-term evolution.
The fusion of digital technologies and IoT usage can transform a traditional farming model into a smart farming model. In smart aquaculture, the integration of artificial intelligence and IoT systems can manage risks, enhance aquatic production quality, and ensure reared species survival.
“Although several advanced options are available for monitoring basic water quality parameters, real-time measurements of more advanced parameters still require further development,” the researcher concluded.
She listed the following conclusions:
- In recent years, the development of information technology and low-cost sensors has enabled monitoring through WSNs, online monitoring systems, and IoT applications allowing real-time monitoring, automatic data collection, and storage.
- Smart systems can predict problems in advance based on water quality changes. Early warning signals are valuable for farmers to detect abnormalities and take action before significant issues arise. However, many modern sensors and monitoring systems require competent users and regular maintenance and calibration.
- All new IoT-based monitoring systems can monitor basic water quality parameters (DO, pH, temperature, turbidity, and salinity), which may be sufficient for regular monitoring purposes. However, more advanced analyses (e.g., off-flavors, cortisol levels) still need to be conducted in a laboratory and cannot be done in real-time.
The study was funded by NordForsk: Sustainable Aquaculture – Research and Innovation Projects.
Natural Resources Institute Finland (Luke), Aquatic Production Systems,
Survontie 9A, FI-40500 Jyväskylä, Finland.
Reference (open access)
Lindholm-Lehto, P. (2023) Water quality monitoring in recirculating aquaculture systems. Aquaculture, Fish and Fisheries, 3, 113–131. https://doi.org/10.1002/aff2.102