A researcher releases a pelican from Strawberry Lake after examining its stomach contents. utah.gov
It’s a centuries-old battle: pelican against trout fisherman. Those lanky intruders pick up all the fish, don’t they? Not so fast, says a team from Utah State University’s Quinney College of Natural Resources studying predator-prey relationships between pelicans and cutthroat trout. Turns out the winged pescatarians might help we catch more fish.
Strawberry Reservoir, a 27-square-mile man-made lake southeast of Salt Lake City, is Utah’s most popular fishery. As part of the state’s Blue Ribbon Fisheries program, it logs 1.5 million fishing hours a year, providing anglers with plenty of opportunities to catch cutthroat trout, rainbow trout and salmon kokani. Its tradition dates back to a catch in 1930, when, according to the Utah Division of Wildlife Resources, Mrs. E. Smith caught the state record non-native cutthroat weighing 26 pounds 12 ounces.
But migratory American white pelicans, which breed in Canada and the northwestern United States and winter in California, Mexico and the Gulf Coast, also stop there to fish. And since cutthroat populations have fluctuated dramatically in the reservoir over the past few decades, lead author Phaedra Budy and her team decided to investigate whether pelicans were to blame.
While cutthroats are well established in the reservoir and its feeder stream system, the adult fish population has fluctuated widely over the past two decades, from 220,000 to 464,000. de Budy captured pelicans over a two-year period and studied their stomach contents. They found that the birds’ diet consisted of 85% Utah sucker, 6% Utah chub, and 3% cutthroat trout. During spawning grounds, when squadrons of pelicans form feeding “fences” that block the mouths of tributaries, the percentage of cutthroats eaten by pelicans increased to 10%. But overall, about 1% of adult cutthroats in the reservoir were taken by the birds, according to the research.
“Because the pelicans are so visible and congregate in large numbers at Strawberry Reservoir, anglers assume they are eating tons of trout,” said Budy crew member Frank Howe. “But the study shows that pelicans aren’t interested in the same species of fish that are prized by human anglers.” Instead, pelicans primarily eat native suckers and chub, species whose populations have increased and are of concern to wildlife managers. Thus, Budy and his study conclude that pelicans are likely doing fishermen a favor by eliminating competing native fish.