Why Do Some Regions Drop Fish into Lakes Using Planes?

From experiments to advertising stunts, dropping things from planes has become a fairly common practice. It's easy to imagine planes spraying crops or fighting fires, but in some parts of the United States, especially in Utah, planes drop fish into lakes. Why would they do that?

Imagine spending a weekend by a lake, far from the city, with beautiful weather and peace and quiet... until a small plane starts dropping fish into the water. You are not losing your mind, and the pilot knows exactly what he's doing. So why? Why would someone in a plane go to the trouble of dropping fish into a lake? The idea seems ridiculous, very costly, and even cruel to the fish. However, the real story is quite different...

Why Fish Are Dropped from Planes

The Utah Division of Wildlife Resources uses the summer season to fly over its high-altitude mountain lakes to restore populations of trout, grayling, and other hybrids. The lakes are extremely popular for much of the year, and without a reliable restoration mechanism, they would run out of fish.

A plane can unload up to 35,000 fish per flight (distributed among a maximum of seven lakes), but it's not just a matter of throwing them out. The fish are raised under special conditions, replicating the temperature and other characteristics of the lakes they will eventually inhabit. At the same time, the fish are sterile, preventing a population explosion that could damage the ecosystem (some anglers often cause problems by introducing species illegally). All fish are counted and weighed for proper distribution.

Another key detail is that at the time of loading, the fish measure between one and three inches (2.54–7.62 cm). That size maximizes the survival rate of the fish when they fall from the plane, currently at 95 percent. The fall is about 45 meters, and with such small fish, the air acts (in part) as a cushion that softens the impact. The use of planes for fish restoration in Utah's lakes began in 1956, but before that it was done on horseback, carrying milk cans, a slower and riskier practice due to the natural difficulties of the terrain.