March 8, 2023 — A new study in the Proceedings of the National Academy of Sciences finds that large-scale fish releases negatively impact ecosystems as a whole, while offering little benefit and some harm to the species they seek to support.
For over a century, fisheries and natural resource managers have bred native fish in captivity and then released them, en masse, into the wild. It’s a popular method for supporting commercially important or threatened populations: More than 2 billion captive-bred Pacific salmon were released in the U.S. in 2016 alone.
Unfortunately, the 150-year-old practice may be doing more harm than good, say researchers at UNC Greensboro, Hokkaido Research Organization, Hokkaido University, and the National Institute of Polar Research in Japan.
UNCG freshwater ecologist Dr. Akira Terui, who led the study and whose research focuses on community ecology, was not surprised by his team’s results. “Many resource managers believe that releasing captive-bred native species into the wild is always a good thing,” he says. “However, ecosystems are delicately balanced with regards to resource availability, and releasing large numbers of new individuals can disrupt that. Imagine moving 100 people into a studio apartment—that’s not a sustainable situation.”