Tom Hafer remembers the first time the fish stopped biting. It was a little over 20 years ago when fiber optic cables were being installed in waters off the coast of central California, where he fishes commercially for spot prawns and rockfish. The fishing was disrupted for “miles and miles,” says Hafer, who has been fishing since the 1970s.

Now, he and many other fishermen are bracing themselves for what could be a much larger threat looming in the water. Offshore wind farms, which are ramping up in the United States, could come at a tremendous cost to fishermen as they are being sited in prime fishing areas. And the process of erecting wind farms and their long-term presence in the water could alter aquatic ecosystems, potentially driving away fish and marine mammals.