Aquaculture is using many more wild fish for food than previously estimated – Mother Jones

Fish farming cages reside on the Mediterranean coast.Images by Karol Serewis/SOPA via ZUMA Press Wire

This story was originally published by Inside Climate News and is reproduced here as part of the Climate Desk collaboration.

In 2022, Fish farms produced an unprecedented 131 million tons of seafood, officially surpassing the global wild-caught fishing industry for the first time, according to a report released in July. Also known as aquaculture, the fish farming sector is often touted as a sustainable way to quickly increase production of crucial sources of fish protein without taking them directly from wild habitats.

But there’s a problem – literally. Some of the main ingredients that farmers feed their fish are, ironically, wild-caught fish. And a new study suggests that the aquaculture industry uses far more wild fish than previously estimated. The investigation is the latest in a wave of criticism against fish farming, which a group of scientists and conservationists say is fueling environmental degradation.

However, global demand for fish is expected to soar in the coming decades. Some experts say that despite its shortcomings, aquaculture is improving and will be a crucial part of the sustainable food supply chain.

Although certain species, such as mussels, primarily eat algae, omnivorous and carnivorous fish require a certain amount of fish in their diets to thrive on farms. To quantify aquaculture’s reliance on wild-caught fish, researchers rely on a deceptively simple equation: how much fish goes into food to produce a certain amount of farmed fish – also known as “fish-in: fish-out.” (FIFO). metric.

In 1997, aquaculturists used a staggering amount of fish in their feed to produce relatively low quantities of farmed fish, with an overall FIFO of about 1.9, according to a 2021 study. That’s almost two fish for every fish that comes out, by weight. In some cases, it took up to 3.16 kilograms of wild-caught fish to produce a single kilogram of salmon. That investigation found that the FIFO ratio declined dramatically in 2017 as the aquaculture industry sought alternative feed ingredients.

However, there are several ways to calculate this metric. A new study shows how different the results can be if we broaden the definition of the “fishing within” side of the equation. Using data from four industry-reported feed composition sources during 2017, researchers calculated the contribution of fish to farmed production in a range of 0.36 to 1.15. This upper limit is about four times the previous study’s estimate.

One of the main reasons for this discrepancy is that the researchers factored in several additional factors into their equation, including updated values ​​for fish oil and something called wild fish trimmings. These are the body parts of marine animals that are removed during the processing of wild-caught fish because they are undesirable to many consumers (think coin toss).

These parts are often used in fish feed, but are rarely accounted for in FIFO equations as they are considered residual by-products. In a separate calculation, the authors also took into account estimates for some of the unintentional animal deaths involved in the fishing process, including the accidental capture of non-target species known as bycatch. This increased the FIFO numbers even further.

“The main recommendation that emerges from the work is to take a closer look at the data,” said study co-author Jennifer Jacquet, professor of environmental science and policy at the University of Miami’s Rosenstiel School of Marine, Atmospheric and Earth Sciences. me by email. “When that happens, what becomes clear is that the picture is not as rosy as the aquaculture industry or the fishing industry would have us believe.”

Small fish like Anchovies and sardines are among the main target species for aquaculture fishmeal. The point is that wild animals also depend on these fish for food. Studies show that the depletion of these stocks can be particularly harmful to seabirds. For example, penguins in Cape Town are declining, largely due to intense fishing pressure on sardines and anchovies, which I wrote about last year.

“One of the takeaways I really liked from this paper was it underlined that we need greater transparency and data availability to really get a good understanding” of the different proportions and species of wild-caught fish used in aquaculture, said Halley Froehlich, assistant professor at the University of California, in Santa Barbara, which studies the sector and was not involved in the study.

However, Froehlich noted that the study’s conclusions may not be as bad for wild ocean fish populations as they seem, because using fish trimmings in food is seen by many as a sustainable option.

“This creates a circular economy,” she told me in a phone interview. “Otherwise, (fish trimmings) would simply be thrown away.”

The tricky part is that fishermen can earn additional income by selling their trimmings, study author Matthew Hayek, an assistant professor of environmental studies at New York University, told me in an email.

This “provides further incentives for fisheries to continue contributing to this value chain”, he said. The study also notes that whole fish from less desirable species on the market – dubbed “junk” fish – are sometimes also added to this mix.

To help mitigate To solve the problem of wild aquaculture fish, scientists and companies are formulating plant-based alternatives, which are increasingly being integrated into the diets of carnivorous fish, especially salmon. This option presents its own set of risks, according to the new study. For example, they say that soy and corn feeding options can increase the generation of agricultural emissions, as well as the consumption of fresh water.

“Our conclusion is that the metrics used to assess the sustainability of aquaculture feed manufacturing left out large aspects of its environmental impacts, both at sea and on land,” said study author Spencer Roberts, a PhD student at Rosenstiel School at the University of Miami. “These omissions helped portray fish and shellfish farming as exceptionally efficient or sustainable. Our research shows that it is most similar to other forms of animal farming, albeit with an unusually high reliance on harvesting wild fish.”

Despite these impacts, research shows that our appetite for seafood is expected to double by 2050. As a result, demand for aquaculture is also increasing. Froehlich stressed that the industry has to find a way to feed fish somehow, and that plant-based foods or other alternative foods — especially microalgae — are the most sustainable options right now. In the end, she said, “there is no such thing as a free lunch.”