Why is oxygenation crucial in sustainable fish farming?
Demand for UK-produced seafood, particularly Atlantic salmon, has increased significantly in both global and domestic markets, with aquaculture contributing over £1.2 billion in value to the UK economy in 2024. Iain McCaffer, expert for aquaculture supply across Scotland and Business Development Manager at Air Products, explores why having a continuous supply of oxygen leading to optimal levels of dissolved oxygen in the water is key to maximizing productivity in fish farms, while navigating seasonal changes to the water, and the number, type and welfare of fish.
The addition of oxygen into fresh or sea water in hatcheries and fish farms supports fish welfare as it supports healthy growth. Sufficient oxygenation levels reduce stress, improve growth rates, strengthen immune systems, and can even lower mortality rates.
Oxygen is not only vital for fish wellness and growth, it also increases productivity and business success in fish farming. Maintaining an optimal level of oxygenation can not only create the conditions for aquaculture stock to thrive, but also boost profitability, supporting the ability to meet growing demand.
Feed efficiency is a case in point. For producers, feed is often the largest production expense, sometimes accounting for 50-to-70 percent of total costs (according to the Food and Agriculture Organization). Creating the perfect production environment is the key to success and this is no different in fish farming, making it a key factor to consider in ensuring efficient farming practices and animal welfare. Low levels of dissolved oxygen can impair feed conversion efficiency, making farming less sustainable. However, boosting feed conversion through more accurate oxygen management can translate into better margins and more predictable performance – all while managing any negative impact on fish welfare and growth.
Oxygen levels
Optimal oxygen levels help to ensure that fish can metabolize feed well, leading to faster growth rates and reduced feed waste – two key factors in profitability.
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 land-based 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.
For those producers choosing liquid bulk supply, advanced telemetry mounted on the storage tanks measures oxygen levels and indicates when a delivery is required. Deliveries are scheduled to ensure constant supply. Telemetry systems reduce administration for our customers and optimize delivery schedules, helping to improve environmental footprint.
For offshore farming, however, where logistics are more challenging to get the oxygen to the pens, we recommend manifolded cylinders to combine large volume supply with transportability.
Careful planning is therefore key, including scheduling gas deliveries in advance, regardless of external factors such as extreme weather. Our role, working with producers, is not only to supply the oxygen, but also to provide ongoing monitoring, guidance and proactive support.
Oxygenation is one of several important factors in sustainable fish farming, and producers work with a broad range of partners to keep their operations running effectively. As an industrial gas supplier with more than 60 years’ experience operating in Scotland, our role is to support our customers with the oxygen they need and to collaborate closely with them as conditions change throughout the year.
Iain McCaffer
Iain McCaffer is Business Development Manager at Air Products. Air Products serves a broad range of industries, including refining, chemicals, metals, electronics, manufacturing, and food, providing essential industrial gases, technologies and applications expertise that enhance customers’ sustainability and improve their operations. The leading global supplier of hydrogen, Air Products is accelerating the energy transition through clean hydrogen megaprojects to decarbonize the hardest-to-abate industrial and heavy-duty transportation sectors.