More fish and seafood on the plate instead of pork, beef and chicken - that would not only be healthier for people, but also for the climate. The problem of marine meals: With its catches, by-catches and trawls, the fishing industry is considered the greatest destroyer of the seas. Aquacultures for shrimps, mussels or salmon are supposed to remedy the situation. Even today, the plants around the world deliver as much as wild catches. But the breeding tanks also have disadvantages: the chemicals and medicines used pollute the water; the production of feed, whether fish or soy meal, destroys habitats elsewhere. Researchers from the University of Melbourne are now making it clear in the specialist journal "Conservation Biology": The breeding does not have to harm nature. Used wisely, they can even help her.
"Algae and mussels grown in coastal waters could remove excess nutrients from urban or agricultural runoff," explains lead author of the study, Kathy Overton. "Toxic algal blooms become less likely." Thanks to the mussel farms in Denmark, for example, pollutants are removed from polluted stretches of sea; in China, algae cultures are to remove all phosphorus from the waters by 2026.
Studies had also shown that the plants provide a habitat for endangered species. The Mediterranean seahorse, for example, which has become rare in some zones, is surprisingly common in mussel farms: it preys on crabs, larvae and fish eggs - and is protected from fishing nets. According to the researchers, the environment even benefits from cages and ropes, because corals, sponges and other sessile organisms can settle on them, and fish find shelter on them. Targetedly populated with native mussels, imported foreign mussels can be pushed out, which can increase species diversity in the long term.
Pollutant filter, protection, basis - despite these advantages, the ecologists emphasize to keep an eye on the overall effects of the systems. "Individual positive aspects do not mean that they are overall good for the environment," explains Tim Dempster, co-author of the study and professor of marine ecology at the University of Melbourne. Only an honest balance sheet prevents the industry from advertising ecological advantages while continuing to destroy rivers and seas.
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