An international group of marine scientists is calling for cuts in commercial fishing for sardines, herring and other so-called forage fish whose use as food for fish farms is soaring. The catch should be cut in half for some fisheries, the scientists say, to protect populations of both the fish and the natural predators that depend on them.

“The message is, if you cut back on harvesting of forage fish, there will be benefits,” said Ellen K. Pikitch, director of the Institute for Ocean Conservation Science at Stony Brook University and chairwoman of the task force that produced a report on the issue that was released Sunday.

The report, “Little Fish, Big Impact,” financed by the Lenfest Foundation through the Pew Charitable Trusts, details how fishing has increased for these fish, which now account for 37 percent, by weight, of all fish harvested worldwide, up from about 8 percent half a century ago. The consumer market for forage fish is relatively small; most of the fish are ground and processed for use as animal feed and nutritional supplements and, increasingly, as feed for the aquaculture industry, which now produces about half of all the fish and shellfish that people eat.

Forage fish are an important link in the food chain, eating plankton and being consumed, in turn, by large fish like tuna and cod, as well as by seabirds and dolphins and other marine mammals. The task force estimated that as a source of food in the wild for larger commercially valuable fish, forage fish were worth more than $11 billion, or twice as much as their worth when processed for aquaculture and other uses.