Sustainability of farmed fish not as bad as previously thought

The sustainability – or rather the unsustainability – of fish has been the subject of much discussion for a long time. Overexploitation of wild fish populations disrupts ecosystems, but the seemingly more sustainable alternative – farmed fish – poses problems of its own. In 2016, for example, the Keuringsdienst van Waarde found out that four kilos of wild fish are required to produce one kilo of farmed salmon. Results from a new study by former Sustainable Development master's student Björn Kok, recently published in the scientific journal Aquaculture, strongly question these numbers. The study shows that those 4:1 ratios – and ratios of other farmed fish species – are probably lower than expected. Thanks to plant-based fish food and Kok's new ‘eFIFO’ method, the ratio of the entire fish farming industry is 1:3 to 1:4 – one kilo of fish in, three to four kilos of fish out.

Man feeding farmed fish

Farmed fish feed is partly comprised of fish meal as a protein source, and fish oil as a source of omega 3 fatty acids. Fish meal and fish oil are procured from wild caught fish, often anchovy. How many kilos of wild fish are required to produce a kilo of farmed fish is calculated using the so-called FIFO ratio: Fish In - Fish Out. There are several methods to calculate the FIFO ratio, but often these methods result in inaccurate and inconsistent numbers. A new method, developed as part of Björn Kok's master thesis, does provide an accurate and consistent forecast of how many kilos of wild fish are needed for one kilogram of farmed fish.

By-products as a free resource

Kok's new method, eFIFO, takes into account shortcomings of other methods. “In a way that does justice to the socio-economic incentives of catching fish for the production of fish meal and fish oil,” he says. “It's a consistent and accurate way of calculating exactly how much wild fish you need to feed your farmed fish.”

In the last years, a lot of progress has been made by replacing animal products.

Björn Kok, lead author paper

Additionally, eFIFO takes into account the use of by-products: fish heads, bones, fins. “Everything except the fillets; about 30% of fish meal and fish oil is produced from these by-products. Other methods see this as a ‘free resource’ and underestimate the FIFO ratio.”

Sustainability labels and certificates still use old methods for their certificates. “Their certificate requirements are set based on old FIFO methods, but if that calculation is not correct, it is difficult to set these goals.”

Person feeding fish in aquaculture pool

Plant-based fish food

Since 2000, partly driven by the high price of fish meal, plant-based protein sources have also been used as an alternative to fish meal. The price of fishmeal went up from 500 to 1,550 USD per ton between the 1990s and 2015, and that of fish oil from 500 to 1,800 USD per ton. Soy, on the other hand, went from 200 to 400 USD per ton in the same period of time. “A lot of progress has been made in recent years regarding the replacement of animal products,” says Kok. But a good source of omega 3 as an alternative to fish oil is not yet widely available, and when vegetable oil is used, the nutritional value of the farmed fish goes down.

The FIFO for salmon, for example, has also fallen sharply since 1995. “With that lower FIFO from plant-based feed, and my more accurate method, you actually get a salmon FIFO of less than 1:1. That is a lot lower than the 4:1 ratio that we know so well. ”

Most sustainable meals

Salmon is not the only fish that Kok has studied. “If you purely look at kilos, carp and tilapia are the most sustainable fish to eat. Pangasius is also doing well. But all three of these fish have a very different – lower – nutritional value compared to salmon.”

So how do other, older methods calculate the FIFO?

Counting double

So how did other, older methods calculate FIFO? Kok explains: “One of the old methods, developed by Albert Tacon and Marc Metian in 2008, separates fish meal and fish oil. Farmed salmon, for example, requires more fish oil compared to fish meal. In order to meet the demand for fish oil, more wild fish must be caught, but the fish meal that is produced along with the fish oil is ‘discarded’ in these calculations. Farmed carp, on the other hand, does not need fish oil at all: when calculating the FIFO ratio of carp, in this case fish oil is ‘thrown away’. In practice, fish oil and fish meal are not discarded. But if you look at multiple types and uses of fish meal and fish oil at the same time, you actually count the amount of wild fish needed to feed farmed fish twice in the calculation. Then it seems as if you need much more fish than is actually the case.”

The other method, developed by Andrew Jackson in 2009, does not take into account the difference in yield of fish oil and fish meal from wild fish. “100 kilos of anchovies yields about 5 kilos of fish oil and 22.5 kilos of fish meal,” says Kok. “Jackson combines the use of fish meal and fish oil and adds up these yields from wild fish, so that the used fish is evenly distributed between the fish meal and fish oil. However, this does not take into account the difference in yield and the economic value of the fish meal and fish oil. Fish oil supplies are often the limiting factor in fish farming, and Jackson's approach obscures the effect of the growing demand for fish oil. As a result, increasing pressure on fisheries to produce fish for fish oil is incorrectly reflected.”

Kok developed this paper as part of his thesis for his Master Sustainable Development – Energy and Materials at the Copernicus Institute for Sustainable Development, Faculty of Geosciences, Utrecht University. He worked closely with researchers and experts from the University of Stirling, University of Massachusetts Boston, Kafrelsheikh University, The University of Edinburgh, IFFO and Harper Adams University. During his PhD at the University of Stirling, Kok will conduct further research into the environmental effects of farmed fish and alternatives to fish feed.

Publication: Kok et al. 2020. Fish as feed: Using economic allocation to quantify the Fish In : Fish Out ratio of major fed aquaculture species. Aquaculture, 528.