Balancing fish and pelican conservation

For birds that make their living eating fish, the 1960s and 1970s were a hard time.  Bioaccumulation of pesticides in and from their primary prey, weakened eggs and led to widespread hatch failure. Bird populations crashed, causing widespread concern. Fast forward 50 plus years, and many of these bird species have made a remarkable comeback, including Idaho’s own American white pelican. A combination of better regulation of some pesticides (like DDT) as well as increased protection through the Migratory Bird Treaty Act have helped tremendously. 

While the comeback of pelicans should be celebrated as a national conservation success story, increases in any predator population often lead to concerns about prey populations. Idaho’s pelican story is no different. During the 1990s, the number of breeding pelicans in Idaho average about 500 breeding pelicans and concern about pelican effects on fish populations were rare. By 2013, the number of breeding pelicans in Idaho peaked at slightly more than 7,700. Increases of this magnitude raised concern among anglers, which led to more attention from biologists looking to maintain a balance between a predator and its prey and to maintain social tolerance for a predatory bird.  

Several intensive research projects were started by Fish and Game biologists. The results indicated that pelicans were having negative effects on certain fish populations in specific locations and decreasing fisheries quality for some anglers.  In some cases, the pelicans were causing declines of native cutthroat trout – Idaho’s state fish or eating a high proportion of stocked trout. The hardest hit areas were the Blackfoot River drainage, several hatchery-supported water bodies across southern Idaho, and Silver Creek. But in contrast, pelicans had little impact on game fish populations in other locations. 

Fish and Game’s biologists worked cooperatively with federal conservation partners like the US Fish and Wildlife Service and Department of Agriculture to develop a plan to manage conflicts associated with pelicans. This plan included efforts to reduce conflict between birds, fish, and anglers and has included the use of a wide variety of techniques to reach a more desired balance. 

Monitoring both bird and fish populations is a central component to this program.  Statewide pelican counts are completed from airplanes every few years to track how pelican numbers and locations are changing over time.  The majority of birds are counted near breeding colonies located at Minidoka National Wildlife Refuge, Blackfoot/Chesterfield reservoirs, and Island Park Reservoir, though non-breeding birds are distributed throughout most of the state. Also, juvenile pelicans are tagged at most colonies to learn about survival and movement to better understand pelican biology and responses to management efforts. On the fish side of the equation, biologists are tracking changes in fish populations and using specialized tags to estimate pelican predation.  This information is helping to develop strategies to improve fish survival and maintain or increase populations.  

In addition, biologists and partners deter pelicans from using certain locations or waterbodies where predation is a big problem. Scaring off pelicans (called “hazing”) might include things like using loud noises, lazers, or simply by the presence of people walking nearby. Hazing often requires diligence, even round-the-clock activity, as once pelicans find a favorite fishing spot, just like us, they don’t like to leave it.  If done effectively, hazing eventually leads to pelicans learning to use other habitats that are less popular with anglers due to more abundant non-game fish populations, which addresses conflict without the need to further reduce pelican populations.

While hazing has worked well in some cases, other more aggressive methods have also been necessary to reduce predation and effects on fish populations elsewhere. In areas where the pelican population is too large and predation is a big problem, fences are used to limit the amount of nesting habitat that pelican may use eventually decreasing local pelican predation in the long run. Furthermore, some pelican eggs are oiled to reduce nest success. This helps stabilize populations and prevent them from continuing to increase.  With more substantial conflict, pelicans are lethally controlled, which serves to reduce predation to a sustainable level or otherwise reinforce hazing efforts.

More work is needed, but these efforts have already started to pay off. As of 2022, the number of breeding pelicans has decreased to slightly more than 3,000, and fish survival has improved.  At the same time, Idaho still supports healthy pelican populations. Finding the desired balance between a protected bird with a remarkable comeback story, native fish species, and introduced game fishes is a non-stop, tight-rope walking act. Circumstances and bird behavior are constantly changing and will continue to do so, requiring that the department remain committed to managing birds, fish, and anglers.