Flying fish devour frogs

The California Department of Fish and Game (DFG) has announced that it will, at least temporarily, stop throwing fish from airplanes at 200 miles an hour.

Call it bizarre. Call it a testament to human ingenuity. But for 50 years the DFG has made a practice of dropping trout fingerlings from airplanes in order to stock naturally fishless lakes and ponds in the Sierra Nevada and Cascade Mountains for the purpose of sport fishing.

The department has announced a one- to three-year moratorium on aerial stocking—not because it kills many of the fish, but because non-native trout in the Sierra may be killing off native frogs, by feasting on their tadpoles and eggs.

Scientists have for years been concerned about the rapid decline of the indigenous mountain yellow-legged frog, once found in abundance throughout the Sierra.

The die-off had been noted as early as the turn of the century, and the introduction of fish has been a prime suspect since the 1920s. The decline seemed to accelerate during the 1950s and 1960s, when DFG began using airplanes to stock lakes otherwise unreachable in the high elevations. As a result, the yellow-legged frog has disappeared from some 80 to 90 percent of its natural habitat, says Dr. Roland Knapp, biologist with UC Santa Barbara’s Sierra Nevada Aquatic Research Laboratory.

Department biologists will study the effects of not restocking until they can determine what impact it has on the frog population. Knapp thinks the department should go further and begin removing the fish from at least some lakes and ponds.

The policy is expected to anger some anglers, but several groups such as Trout Unlimited and the publication Field and Stream have indicated support. Knapp said trout populations in areas where restocking has ceased, such as Yosemite and other National Parks, have actually proven to be self-sustaining.

Knapp borrows a phrase from one of the founders of wildlife biology, Aldo Leopold, as he explains why people should care about a bunch of yellow-legged frogs: “The first rule of intelligent tinkering is to save all of the parts,” said Knapp.