There's a catch: recreation takes toll on marine fish.

Sport-fishing isn't just a tiny, harmless nibble on saltwater-fish populations, according to a new analysis of federal data.

For species flagged for special concern in U.S. waters, sportfishing accounts for 23 percent of the harvest, says Felicia Coleman of Florida State University in Tallahassee. The percentage is even higher for certain regions. In the Gulf of Mexico, recreation takes 64 percent of the catch for troubled fish stocks, Coleman and her colleagues report in an upcoming Science.

Coleman dates her concern about the topic to her years on the federal council that regulates fishing off the Gulf Coast. "It was clear that recreational fishing was an enormous industry," she says, yet common wisdom held that it accounted for only about 2 percent of the fish landed and not released back into the water. "That seemed as if it was a bit of an underestimate," she says.

A first look at online data from more than 22 years of monitoring by the National Marine Fisheries Service does yield about that percentage, she and her colleagues report. However, a closer examination reveals gaps, such as the exclusion of data from the charter-boat fishing in the Southeast.

Coleman and her colleagues worked out ways to fill in the gaps. Their new estimate for the annual recreational landings for all species, not just the troubled ones, comes to 4 percent. In all the calculations, bycatch, discards, and catch-and-release fish are omitted.

The team removed from its analysis menhaden and pollack, the two species with the largest commercial catch. These fish are neither flagged for concern nor much targeted for sport. For the remaining 907 saltwater species, sportfishing accounted for 10 percent of landings.

The researchers then focused on fish that the National Marine Fisheries Service has assessed as either "overfished" or "experiencing overfishing." Coleman and her colleagues determined, for example, that recreation accounts for 59 percent of red snapper landings in the Gulf of Mexico and 93 percent of red drum landings in the southern U.S. Atlantic.

The researchers also calculated the share of recreation landings by region for the troubled species: 12 percent in the Northeast, 38 percent in the southern Atlantic, and 59 percent off the Pacific Coast.

The data may suggest a need for new limits on recreational fishing for some species, say Coleman and her colleagues. Often, anglers are permitted to catch only a limited number offish of a given species, but regulators rarely limit the number of people who may fish.

Michael Sissenwine, chief science advisor at the National Marine Fisheries Service in Silver Spring, Md., responds that the impacts of recreational fishing "have always been recognized" by fisheries managers.

According to Andrew Rosenberg of the University of New Hampshire in Durham, a former deputy director of the National Marine Fisheries Service, the role of sportfishing hasn't always been appropriately factored into management plans, "out often for political reasons, not lack of knowledge."

Marine ecologist Jane Lubchenco of Oregon State University in Corvallis welcomes the new report because, although some scientists worried about the impact of recreational fishing, "nobody had the numbers," she says.