For a long time there was hope that we could avert overfishing of the seas simply by cultivating fish, algae and mussels ourselves. But this system of aquaculture is not only ecologically controversial, it will also not be sufficient to cover global demand, as scientists have now calculated. According to this, aquaculture production is simply growing too slowly to ever be able to feed the world population. In addition, the breeding stations are distributed very unevenly around the world, which would disadvantage some countries in the long term.
In aquaculture, aquatic creatures such as fish, shrimp, algae and mussels are bred and kept in large cages or nets. While algae and mussels can simply filter their food out of the water, fish and shrimp need to be fed. Their diet consists mostly of fishmeal and oil from wild fish. Because fish still have to be caught and the fish food also pollutes and over-fertilizes the sea, aquaculture is controversial. Nevertheless, the system of aquaculture or aquafarming has long been treated as an opportunity to become largely independent of wild fish stocks, i.e. to be able to feed the world without overfishing the seas.
Balance sheet from 70 years of aquaculture
Researchers led by Rashid Sumaila from the Canadian University of British Columbia have now extrapolated whether it is really that easy. To do this, they evaluated publicly available data from the Food and Agriculture Organization of the United Nations. It listed the production volumes of farmed aquatic animals and plants between 1950 and 2018 for various countries. Sumaila and his colleagues first identified the ten most commonly farmed species and the leading fish farming countries worldwide.
In order to find out whether the world's population can be fed with the farmed fish, mussels and algae, Sumaila's team also calculated how much the production of popular marine life has increased in recent years. Based on this, it examined whether aquaculture could meet human needs for fish and seafood by 2030. The researchers calculated that 173 million tons of aquatic life would be needed. However, we are currently producing just 82.2 million tons. The goal can therefore only be achieved with high growth rates.
Not to satiate world hunger through aqua farms
But that is not in prospect: "We show that the growth rates in aquaculture have already peaked in all of the cases examined and are now declining," report Sumaila and his colleagues. This peak had already taken place in 1996. Although the production of the ten most important cultivated species has continued to increase since then, this increase is becoming smaller and smaller. According to the researchers, the aquaculture of Atlantic salmon has been hardest hit by this decline. While their growth rate was 314 percent in 1970, it has now fallen to 0.9 percent.
"The global hunger for fish and seafood cannot be satisfied primarily through aquaculture," summarizes co-author Rainer Froese from the GEOMAR Helmholtz Center for Ocean Research in Kiel. Even with technological innovations, the gap can no longer be made up. That being said, more animals wouldn't directly mean more food. Large aqua farms are prone to diseases and toxic algal blooms.
Return to fishing recommended
According to the researchers, even if it were technologically, ecologically and economically feasible to meet all or at least most of the world's fish needs from aquafarms, there is still an ethical reason that would prevent it. Aquaculture production is distributed very unevenly around the world. 90 percent of the total production is in Asia, 60 percent in China alone. The remaining ten percent is divided between the other continents, with Europe having a share of four percent. In the long term, this imbalance would mean that many countries would only be able to meet their needs by importing aquatic animals from Asia, the researchers explain. That would be expensive and would lead to hunger, especially in developing countries.
Sumaila and his colleagues advocate not just relying on aquaculture, but also developing sustainable strategies for catching wild fish. "A conversion of the fishing industry to an ecologically compatible fishing would offer a significantly higher future potential," explains Froese. For example, Europe alone could increase its catches by around five million tons if it were to rebuild and properly manage the fisheries. That would be more than the annual yield that Europe currently gets from its aqua farms. At the same time, comprehensive new fisheries regulations could also prevent marine biodiversity from suffering indirectly as a result of catching forage fish for aquaculture.
Source: GEOMAR Helmholtz Center for Ocean Research Kiel; Article: Frontiers in Marine Science, doi: 10.3389/fmars.2022.984354