The Changing Dynamics of Predatory Fish in the Columbia and Snake Rivers
Over nearly a decade, the management of walleye and bass populations in the Columbia and Snake rivers has undergone significant changes. Initially, Oregon and Washington removed bag and size limits on these fish to support the conservation of salmon and steelhead. However, times have changed, and the ecological landscape has evolved dramatically.
While the salmon family continues to struggle, the presence of non-native species such as walleye and bass has increased substantially. These invasive predators have expanded their ranges, with walleye particularly notable for their spread into the Snake River up to the Salmon River. This shift highlights the complex interplay between native and non-native species within the river systems.
Walleye were first introduced into Lake Roosevelt (Grand Coulee Dam) in the mid-20th century for both food and sportfishing purposes. From there, they gradually made their way downstream, becoming a common catch by 1980. Today, their presence is widespread, from Vancouver and Portland to the Willamette system’s Dexter Dam and Lookout Reservoir.
Efforts are currently underway in Lake Roosevelt to eliminate northern pike, aiming to prevent them from following a similar path as walleye and bass. This proactive approach underscores the importance of managing invasive species to protect native ecosystems.
A Nostalgic Reflection on Walleye Fishing
In 1988, a memorable walleye fishing trip took place out of Boardman, where the winner of that year’s Oregonian Fish Story Contest was taken on a journey. The experience included catching limits weighing between seven to 13 pounds, using worm harnesses while trolling along the bottom near submerged mounds. The late guide Mike Jones encouraged the winner’s wife to mount her 13-pounder, calling it a “wall hanger.” He emphasized that nothing over 12 pounds would be filleted, highlighting the significance of these catches.
Jones also remarked, “You can’t fish the walleye out…They’re here to stay,” a statement that proved prophetic. The walleye population has indeed become a permanent fixture in the region.
The Impact of Invasive Species on Salmon Populations
The spreading influence of walleye has prompted a reevaluation of predator control strategies. The pikeminnow bounty program, initiated in 1991, aimed to reduce the impact of predatory fish on juvenile salmonids. Early results from the John Day pool highlighted the significant role of pikeminnows in juvenile losses, with pikeminnows accounting for 78 percent, walleye for 13 percent, and smallmouth bass for 9 percent.
However, the dynamics have shifted. Biologists now focus on loss reduction rather than assigning blame. A 10-20% annual reduction in pikeminnow numbers corresponds to a 20-40% annual savings in the loss of juvenile salmonids to all three species.
Grant Waltz, the pikeminnow program leader for the Oregon Department of Fish and Wildlife, notes that the Columbia River system is dynamic and varies from pool to pool. Factors such as climate change, warming water temperatures, snowpack, dam operations, agricultural diversions, avian predation, and interactions among predatory fish all contribute to the complexity of the ecosystem.
Ecological Considerations and Future Outlook
Waltz emphasizes that the removal of one predator can lead to another filling its ecological niche, a phenomenon known as “compensation.” This complexity requires ongoing monitoring and adaptive management strategies.
Biologists use electro-shocking techniques to capture and examine predatory fish, comparing current findings with historical data. Crayfish, shad fry, crustaceans, and baby lamprey often share the diet of these predators, with walleye notably preying on salmon in Bonneville’s tailraces.
Despite the challenges, the bounty program has shown success in reducing juvenile salmon losses. However, Waltz cautions against applying these results uniformly across all pools. The distribution of walleye and bass varies, and localized efforts remain crucial.
Implications for Sport Anglers and the Future of Fishing
For sport anglers, the expansion of walleye and smallmouth bass presents both challenges and opportunities. While concerns about salmon returns persist, the bounty program has likely prevented even greater declines in salmon populations. The removal of pikeminnows has played a critical role in this effort.
Additionally, the growth of walleye and bass populations offers a glimpse into the future of angling. Unlike salmon, which face uncertain prospects, these species are expected to remain a staple in the region. Their presence may redefine the fishing landscape, providing new opportunities for anglers and communities reliant on fishing activities.
As the ecosystem continues to evolve, the balance between native and invasive species will require ongoing attention and adaptive strategies to ensure the sustainability of the Columbia and Snake rivers’ fisheries.
