Farming Fish Not Environmentally Sound

 

Spencer Roberts, Jennifer Jacquet, Patricia Majluf, Matthew N. Hayek; Feeding Global Aquaculture; 2024/10/18; DOI: 10.1126/sciadv.adn9698; Journal: Science Advances Volume: 10; Issue: 42; Feeding global aquaculture

The below article is excerpted from the article cited above and the Press Release from the University of Miami and some thoughts from "Salmon Wars" by Douglas Frantz and Catherine Collins.

 

A study published this month in the journal Science Advances suggests that fish farming, or aquaculture, relies on much larger quantities of wild-caught ocean fish than previously calculated. These miscalculations have helped to portray fish farming as uniquely efficient or sustainable. Instead, the above cited study portrays fish farming like other forms of animal farming, albeit with a uniquely high reliance on wild fish extraction.

This wild fish extraction to feed the farmed fish also diverts millions of tons of food-grade fish (e.g., anchovies and sardines) and nutrients from countries with high rates of hunger to farmed aquatic animals (e.g., salmon and shrimp) intended for luxury markets of the world. Millions of people in Africa rely on fish for protein.

For too long, the fish-farming industry has wrapped itself in a cloak of virtue, asserting that it is feeding the world and putting healthy food on the table. The use of fish trimmings (heads, tails and guts) in feed is seen by many as a sustainable option and evidence of a circular economy in fish farming.  That is an illusion. The use of by-products and trimmings has not phased out the capture and use of whole wild fish in feeds for aquaculture. The offshore aquaculture industry is growing so rapidly that the wild-caught fish is not being replaced in their feed. Instead, other feed sources are just supplementing wild fish use.

Small fish such as anchovies and sardines are among the main species targeted for aquaculture fishmeal. The issue is that wild animals depend on these fish for food as well as the local communities. The 3,400-mile-long Atlantic coast of West Africa and the Pacific coast of Peru have been overfished to the point of threatening the viability of the native communities who depended on fishing and fish for survival. Penguins in Cape Town are declining largely due to the intense fishing pressure on sardines and anchovies and other species are also under stress.

The research cited above provides a reassessment of the "fish-in:fish-out" (FI:FO) ratio for global fed aquaculture to evaluate the efficiency and sustainability of aquaculture. By analyzing multiple industry-reported datasets, the researchers provided a range of estimates and highlighted uncertainties in current reporting practices. They found that the aquaculture industry relies more heavily on wild fish extraction than previous research had suggested.

The findings indicate that the ratio of wild fish inputs to farmed fish outputs is 27% to 307% higher than previous estimates, ranging from 0.36 to 1.15 compared to an earlier estimate of only 0.28. When accounting for wild fish mortality during capture and excluding unfed aquaculture systems, the ratio rises even further to 0.57 to 1.78. (The lower number reflects the use of terrestrial crops in some aquaculture species.) For carnivorous farmed species like salmon, trout, and eel, wild fish inputs likely exceeded twice the farmed fish biomass produced.

"Our study reveals that the aquaculture industry relies more heavily on wild fish extraction than previous research has suggested,” said Spencer Roberts, a doctoral student at the Rosenstiel School in the Department of Environmental Science and Policy, and lead author of the study. “This demonstrates the scale at which aquaculture could be impacting marine ecosystems."

The research team's approach included accounting for previously overlooked sources of wild fish in aquaculture feed, such as trimmings and byproducts from wild-caught fish. They also incorporated collateral fishing mortality, including "slipping"—a practice where unwanted catch is released but a large portion of the animals often do not survive. By analyzing multiple industry-reported datasets, the team provided a range of estimates and highlighted uncertainties in current reporting practices.

The researchers stress that while their study provides a more comprehensive view of aquaculture's environmental impacts, further research is needed to fully understand the sector's effects on issues such as nutrient pollution, habitat destruction, and the spread of diseases to wild fish populations.

Matthew Hayek, an assistant professor in the Department of Environmental Studies at New York University and the  corresponding author of the study, stated "It's crucial that we have a more complete understanding of the industry's impact on both marine and terrestrial ecosystems and reduce these uncertainties.” He emphasizes that even with the wide uncertainty ranges reported, the impacts are still larger than previously reported, and “most offshore finfish aquaculture facilities produce carnivorous fish, and therefore are responsible for depleting far more fish from the ocean than what they can produce.”