___________________________________________________________________________________________________ Sustainability
How do you know what level of dissolved oxygen needs to be achieved? The correct level for ideal welfare and production will change throughout the year, based on various parameters. In fact, we’ ve seen first-hand over many years working closely with fish farmers that seasonal changes have a significant impact because they influence water temperature, salinity, oxygen solubility, and overall pond or tank conditions.
We know that in warmer months, water temperature rises, reducing the solubility of oxygen, ultimately meaning there is less dissolved oxygen available for the fish. At the same time, fish metabolism and feeding rates increase in warm water, creating a higher oxygen demand. Producers therefore need to consider how this imbalance can lead to stress, slower growth, and, in extreme cases, mortality if the oxygen levels drop too low. During these months, we’ ve seen producers need to increase the oxygenation rate to return the water to the right balance.
In colder seasons however, while oxygen solubility improves, fish activity and feed intake decrease. Demand for oxygen can typically reduce marginally in these months and our work ensures it can be carefully managed, so the levels do not dip too low, and we maintain efficiency and consistency in supply. Seasonal variations also affect algae growth and decomposition, which can further alter dissolved oxygen levels.
Oxygen levels for fish farms need to be consistently monitored, particularly during the summer months when oxygen depletion is most likely. Our experience working with producers means we can support them to pinpoint the correct concentration of oxygen based on source water, temperature, organisms and fish quantity.
With oxygen playing such a vital role in efficient and sustainable farming practices, it’ s critical that producers have the right mode of supply in place. Even a short interruption to supply can have a marked impact on the growing environment for the fish in the farm or hatcheries, potentially leading to direct economic losses for the producer.
Oxygen can be supplied to the aquaculture sector in a range of ways – including individual gas cylinders, large volume manifolded cylinder packs and larger volume liquid bulk supply service.
The volume of oxygen and mode of supply is dependent on several factors such as the location of the hatchery or fish farm and the system already in place, the temperature of the water, the type and quantity of fish being produced, production density and the stage of the production cycle. For example, in recirculating aquaculture systems, the oxygen supply needs to be continuous compared to open systems, making the choice of supply mode very important. There is, however, a solution available for each requirement.
Our expertise involves providing consultancy and guidance to our customers in making supply decisions for their business, as well as ongoing oxygen monitoring once in place. Different supply modes are not only needed due to the location of the fish farm, but also depending on the type of farm or tank that’ s being used, and whether it’ s landbased or offshore.
We know, for example, that many fish farms operate in Scotland, where the supply mode is often through liquid supply in tanks( for medium to large scale land-based operations) or in cylinders( for smaller operations, very remote sites where tanker access is difficult, or for offshore sea pens). Where necessary, we’ ve worked with customers to help manage the sensitivities and challenges of the rural areas that we service. This can include painting tanks to be sympathetic to the surrounding scenery.
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