Land-based aquaculture is of increasing interest; however, the supply of fresh unpolluted water is becoming scarce in many areas of the world. This will put increasing pressure on aquaculture businesses to develop recirculation systems . Water quality is one of the most critical factors in aquaculture. Optimum water quality is essential for survival rate as well as growth rate of fish in the different phases of the life cycle and maximise the productivity per m3 effective tank volume. Fish are often overfed and there is considerable discharge of food spill, faeces and gases in the water. In addition to this, the fish consume the oxygen in the water. With increasing reuse and recirculation of water, monitoring water quality becomes of vital importance.
Supersaturation of gases in aquaculture (nitrogen [N2] argon [Ar] and carbon dioxide [CO2]), are a big concern because these gases account directly or indirectly for some 30% of fish mortalities in aquaculture . However, recognition of this problem can be slow because the impacts of low levels supersaturation can be subtle, variable and confused with other problems and is usually only recognised after conditions become lethal. Extended exposure to low levels cause fish stress, deplete their energy reserves and immunity and increase vulnerability to disease, with mortality rates up to 10% being very common .
By producing a technology that is capable of continuously monitoring the gas saturation of the water within the aquaculture tanks, we will significantly reduce the issue of gas supersaturation and thereby reduce the loss of fish in aquaculture, increasing the income for the large numbers of SMEs in the industry.
Our project will develop an integrated monitoring and control system for the critical operation parameters of air/water ratio, salinity, N2, CO2, O2, Argon, temperature, pressure, rate of flow and pH. The monitoring system will be low cost, simple and low energy which will make it suitable for a wide variety of aquaculture applications. The monitoring system will be able to monitor all the above in one simple unit to allow for ease of use. The system will be fully automatic, so the farmer will not need to control degassing equipment or pumps himself. The control system will be programmed to maintain optimised conditions for specific fish species at each stage of their growth.
There are a number of technical barriers to be overcome:
- The identification of the optimum water quality conditions for all species of farmed fish at each stage of their life cycle
- The corrosion of materials caused by long term contact with salt water – we will need to identify a material that will have minimal or no corrosion in addition to not affecting the water quality.
- A method of monitoring all these characteristics in one simple, low cost unit
- Integration of the low-cost monitoring device into a feedback-controlled system that automatically operates dosing, degassing and feeding units for use with existing infrastructure.
- To create an understanding of the effects of dissolved gases in water on fish growth rate and oxygenation of water for different species at different stages of life to specify the demands in terms of the feedback system
- To characterise the other factors in water affecting the dissolved gases such as temperature, pH, salinity and the effects of other pollutants such as food waste and fish faeces.
- To produce a database of the requirements of the life cycle of different fish species utilising data provided by the SME-Associations involved in the project
- To produce a fully integrated monitoring system for air/water ratio, salinity, N2, CO2, O2, Argon, temperature, pressure, rate of flow and pH to all be measured within the same unit.
- To define a suitable material and design for the monitoring system to allow permanent submersion in saline water without suffering from significant corrosion for a period of at least 3 months.
- The production of algorithms and software for the control system to relate the results from the tank with the degassing and other control equipment used in fish farming.