Fisheries scientists are continuing an experiment with fish that respond to a dinner bell like Pavlov's dogs, despite a pending US court order that could stop the study.

Will young sea bass come to the call of a bell? Credit: S. Senne/AP

Food & Water Watch (FWW), a non-profit organization in Washington DC, is suing to halt research by scientists at the Marine Biological Laboratory in Woods Hole, Massachusetts, until further environmental analysis is completed. The laboratory has until 5 September to answer the organization's criticisms, but FWW is confident of a ruling on its request for a temporary injunction before then.

"The purpose of the study is to see if we can selectively harvest hatchery-raised fish after they're released into the ocean," says project leader Scott Lindell. If successful, the research would have implications for restocking wild fish populations and commercial fish farming.

The 5,000 hatchery-raised black sea bass (Centropristis striata), which associate a tone with feeding, moved in to their open-sea cage on 17 July. The geodesic 'aquadome' is anchored to the sea floor of Buzzards Bay in Massachusetts. The bass will be released this month and the researchers will then test whether the fish return to the dome when they hear the tone.

The experiment could pave the way for fish ranching in the open sea. "It's like cattle ranching. You don't put up fences, you let them roam around," says Michael Tlusty, director of research at the New England Aquarium in Boston, Massachusetts. But some say that such a system would have limited use in commercial fisheries. "It is more a biological curiosity than of any relevance to actual wild capture or aquaculture," says Ray Hilborn, a fisheries scientist at the University of Washington in Seattle.

Sound-trained fish could help efforts to boost wild populations, Lindell says, because released hatchery fish would return at the tone for a decent meal while they adjust to open-sea life. "It's to give them sort of an energy packet while they forage," he says.

FWW says that the US Army Corps of Engineers, which issued the permit for the underwater structure, failed to conduct a thorough enough environmental investigation. It is concerned that fish food and waste could pollute the waters around the cage, and that wild fish might learn to associate human activity with food.