The smallest fish in the sea are more than twice as valuable when they’re eaten by bigger fish than when they’re caught by humans, according to a report released Sunday by a scientific task force.

The 120-page analysis by the Lenfest Forage Fish Task Force — a group of 13 scientists specializing in everything from fish ecology to marine mammals and seabirds — underscores the growing concern researchers have about the fate of forage fish, including anchovies, mehaden, herring and sardines that serve as food for bigger fish, sea birds and marine mammals.

Forage fish account for 37 percent of the world’s commercial fish catch, with an annual value of $5.6 billion. (Only 10 percent of forage fish caught are eaten by humans; the remaining 90 percent are processed into fish meal and fish oil, which feed livestock and farmed fish.)

But the team of scientists, who worked for three years on their analysis, concluded that forage fish support $11.3 billion worth of commercial fish by serving as their prey. In the North Sea, for example, sand eels help sustain cod, and tuna in the eastern tropical Pacific Ocean feed on sardines.

The group’s economic analysis did not include the value forage fish provide to sea birds and marine mammals, many of which are highly dependent on them. University of Washington conservation biologist Dee Boersma, one of the task force’s members, has conducted studies showing that the breeding success of Magellanic penguins is directly related to how far they had to forage for food. If they could find fish between 30 and 50 miles of their colony they produced two chicks; if they had to travel more than 90 miles away, they had one; and if they had to go 125 miles, they had none.

In an interview, Boersma said that with fewer forage fish, seabirds were having to travel farther for less food. “Suddenly, instead of 90 percent, you’re settling for 10 percent. That’s what’s happening to seabirds. When fish is not there, they don’t do as well.”

Ellen Pikitch, chairman of the task force and executive director of Stony Brook University’s Institute for Ocean Conservation Science, said society may need to reassess its reliance on small marine species to sustain the growing aquaculture trade. Farmed fish accounts for roughly half of the world’s commercially sold fish.

“People don’t understand how massive this fishery is,” Pikitch said, referring to how many forage fish are processed. “It seems we may be on a collision course at some point, where increased demand is going to pull the rug out from under the ocean ecosystem.”

The issue has become increasingly important for fishery managers in the mid-Atlantic, who voted in November to cut the amount of menhaden that can be harvested annually from 183,000 metric tons to 174,000, out of concern that the fish have been depleted.

One company, Omega Protein, took 160,000 metric tons of menhaden — 80 percent of about 450 million fish harvested in 2010 — off the coast of Virginia, which is the only state that allows industrial fishing of menhaden.

Edward D. Houde, a task force member and a professor at the University of Maryland’s Center for Environmental Science at the Chesapeake Biological Laboratory, said the task force concluded that fishery managers should leave at least 40 percent of adult forage fish in the sea. Menhaden support a range of species in the Chesapeake Bay and Atlantic Ocean, including striped bass, osprey, bald eagles and brown pelicans.

Traditionally, fishery managers aim to leave 20 percent of adult fish unexploited. The Atlantic States Marine Fisheries Commission will finalize its mehaden rule next year, and is crafting limits that would ensure at least 15 percent of adult menhaden, and perhaps as much as 30 percent, are left to spawn in the ocean and its tributaries after the yearly harvest. Current limits are to leave at least 8 percent.

“That would not be as precautionary as we’re recommending in the task force,” Houde said, though he said it was a step in the right direction. “It’s still very hard for them to reduce fishing, which means reducing catches and reducing profits. It’s not easy for them to take these precautionary steps that are important for the environment.”