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1994 Columbia River Basin Fish and Wildlife Program |
| Council document 94-55 | |
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5.7 Reduce Predation and Competition
Hydropower development in the Columbia Basin resulted in an environment that favors salmon predators. Additionally, introduction of non-native species, development of some hatchery programs, and greatly increased numbers of seals and sea lions as a result of protection of the Marine Mammal Protection Act, have resulted in an increase in the adverse effects of predation and competition on salmon. Conditions beneficial to predatory fish include increased predator spawning habitat, slightly warmer water temperatures, and the introduction of millions of hatchery fish that are diseased and ill-suited to escape predation. Other factors that improve predator success include concentrations of smolts at hydropower facilities and the incapacitation of smolts passing through generator turbines. Hydropower development also increased predation by birds. Predator vulnerability may also be increased for juvenile fish passing through existing bypasses and sluiceways. The introduction of non-native species, as well as certain hatchery management practices, have also resulted in increased competition for a number of the weak runs.
In this section, the Council calls for measures to reduce predation and competition, including a squawfish management program that employs targeted fisheries or other measures to achieve the removal of more than 20 percent of the squawfish population, with the expectation that this will result in more than a 50-percent reduction in the present consumption of juvenile salmonids. This is a modification to the current predator control effort and increases the rate of squawfish removal, which will progressively reduce predation on smolts. A comprehensive monitoring and evaluation program will evaluate the effectiveness of predator control efforts. These efforts will then be modified, if necessary.
5.7A Performance Standards for Reducing Predation
Bonneville, Corps of Engineers and Mid-Columbia Public Utility Districts
5.7A.1 Squawfish: Reduce squawfish population by more than 20 percent in the Snake and Columbia rivers with the expectation that this will result in more than a 50 percent reduction in the present consumption of juvenile salmonids.
5.7A.2 Shad: Explore the population ecology of shad to determine effective methods for control and develop programs to eliminate shad from the Columbia River system above Bonneville Dam and reduce the shad population below Bonneville Dam.
5.7A.3 Other Non-Native Fishes: Reduce numbers of non-native fish wherever they exist with listed species or weak runs, and curtail recruitment of non-native fish into the habitats of listed species and weak runs.
5.7A.4 Steelhead: Evaluate the extent of residualism (precocious males) in hatchery steelhead populations. Determine the causes of residualism in hatchery steelhead populations and initiate actions, based upon the results of these determinations, to reduce the incidence of residualism by at least 50 percent to reduce the potential for residual hatchery steelhead to prey on or compete with natural salmon/steelhead populations.
5.7A.5 Trout: Use alternative planting strategies for release of hatchery trout which will reduce predation and competition to acceptable levels. Evaluate effect of native trout on survival of weak stocks.
5.7A.6 Birds: Monitor and assess predation by birds and identify non-lethal methods of control.
5.7B Predation Control Actions and Evaluations
Bonneville and Other Parties
Squawfish
5.7B.1 Continue implementation of the current squawfish project and increase the rate of squawfish removal thereby progressively reducing predation on smolts.
5.7B.2 Document current population dynamics, life history and behavioral attributes of squawfish throughout the migratory corridor to identify times and places where squawfish are vulnerable to control measures, to document sources of recruitment and to provide the data necessary to monitor responses of squawfish populations to control measures.
5.7B.3 Monitor the squawfish program effectiveness directly; i.e., measure total consumption by the predators, or rate of survival by the salmon, or both, if feasible. Other monitoring indices such as exploitation rates in the fisheries and age structures of the squawfish populations, are ancillary and informative for analyzing the program operations. The control program will be implemented and evaluated in a phased process, beginning at one or two carefully selected locations and then expanding to more areas. Evaluations should quantify changes in predator populations and in the overall rate of predation. Provide an annual report to the Council on the effectiveness of this program.
5.7B.4 Expand the program that monitors fish communities and populations to measure and assess the effects of squawfish control. Of particular interest would be other salmon predators and competitors, and any changes in their impacts on salmon concurrent with changes in squawfish population levels.
5.7B.5 Explore the development of methods to reduce squawfish population numbers at all appropriate life stages. Continue the present fisheries (sport reward fishery, dam angling and commercial harvest) as interim measures until more directly effective methods of squawfish control are found and implemented.
5.7B.6 Explore the development of methods to capture squawfish by concentrating them through flow manipulation or other means into slack water areas where they would be more or less isolated from migratory salmonids and more vulnerable to capture.
5.7B.7 Examine potential conditions and feasibility for the use of Squoxin.
5.7B.8 Implement a formal process for annual peer review of the program performance.
Shad
5.7B.9 Explore population ecology of shad to determine the extent of adverse interactions with salmonids and identify effective methods for control.
5.7B.10 Concurrent with exploration of population ecology, develop programs to eliminate shad from the Columbia System above Bonneville Dam. Alternative upstream passage designs should be evaluated to find methods for preventing the upstream passage of shad while allowing salmon and steelhead to pass. The program will have to account for the very large biomass of adult shad that enter the system each year, and include components for separation of shad from salmon, their removal from the waterway, and their utilization in some responsible way.
5.7B.11 Managers should use whatever methods are available to reduce the numbers of shad that spawn below Bonneville Dam.
Other Non-Native Fishes
5.7B.12 Wherever non-indigenous species exist with listed species or other weak runs, use any measures practicable to reduce populations of non-indigenous species. In addition, recruitment of these species into habitats of the listed species should be curtailed.
5.7B.13 Sport harvest of non-indigenous species should be allowed anytime, with no bag limit or size restrictions.
5.7B.14 There should be no programs that would directly improve habitats, production, or survival of introduced species.
5.7B.15 Monitor populations of non-indigenous species as part of the program that monitors reservoir fish populations and communities that was recommended for squawfish control. These data and other information should be used to identify potential times and places that populations of these species are vulnerable to control measures.
5.7B.16 Application of the provisions and authority of the Non-indigenous Aquatic Nuisance Prevention and Control Act of 1990 should be evaluated and pursued as a vehicle to control and reduce the populations of non-native fishes in the area inhabited by the listed species.
Steelhead
5.7B.17 Assure that all hatchery steelhead are released at a time and in a physiological condition that will encourage rapid migration through the Columbia River system to reduce the extent of interactions with natural stocks of salmon and steelhead.
Trout
5.7B.18 No hatchery trout should be released into waters essential for spawning and rearing of the listed species or weak stocks unless alternate planting strategies can be used that will reduce predation-competition to acceptable levels.
5.7B.19 Evaluate the effect of native trout on survival of the listed species in areas where the listed species and other weak stocks cohabit.
Birds
5.7B.20 Add predation by birds in the Columbia and Snake river reservoirs as part of a continuing monitoring and assessment program, including examination of stomach contents.
5.7B.21 Initiate a comprehensive study immediately to evaluate salmonid consumption in the estuary. Emphasize Caspian tern and cormorant colonies utilizing manmade dredge-spoil islands in the lower river.
5.7B.22 Identify non-lethal methods of control. For example, netting or other materials can be employed to interfere with the ability of birds to reach the fish, or manmade habitats can be altered to limit population size.
Corps of Engineers, Bonneville and Federal Energy Regulatory Commission
5.7B.23 Evaluate and expeditiously implement measures to reduce smolt mortality due to fish and avian predation at bypass system release sites. Currently, the outfalls dump the fish into the river a short distance downstream from the dams, usually near the shore in an area likely to have high predation rates. Measures should be designed to disperse juvenile fish releases below dams and should include, but not be limited to, modifications to existing bypass system outfall structures, modification of project or bypass system operations.
National Marine Fisheries Service
Additional information is needed regarding the extent of marine mammal impacts on salmon populations.
Marine Mammals
5.7B.24 Investigate the relationship between the Endangered Species Act and the Marine Mammal Protection Act. Seek language in the Marine Mammal Protection Act that will permit the Secretary of Commerce the authority to allow the lethal removal of pinnipeds once all reasonable non-lethal means of deterrence have been exhausted. This type of control should be applied to pinnipeds affecting all weak stocks of salmon and steelhead, not only those that are listed.
5.7B.25 Develop a protocol for marine mammal predation control for immediate implementation in the event that evidence indicates control is needed to support listed species? recovery.
5.7B.26 Collect data on marine mammal distribution and abundance on a year round basis.
5.7B.27 Collect marine mammal food habit data, including the examination of fresh stomach contents from seals and sea lions in an area where they are assumed to be predatory on salmon.
5.7B.28 Observe and document the incidence and location of salmon predation. This should include the incidence of removal of salmon from fishing gear.
5.7B.29 Radio-tag chinook as they enter the mouth of the lower river so they can be tracked to ascertain their interactions with the marine mammal population.
5.7B.30 Radio-tag seals and sea lions.
5.7B.31 Radio-tag scarred fish at Bonneville Dam to determine their survival during the up-river migration.
5.7B.32 Conduct captive predation studies to validate the causes of scarring and determine size and species preference.
5.7B.33 Develop a computer model to simulate the effects of removing non-breeding male sea lions.
Mid-Columbia Public Utility Districts
Predators in Mid-Columbia
5.7B.34 Subject to Federal Energy Regulatory Commission approval, develop a coordinated study plan with the fishery managers to evaluate the extent of predation on juvenile salmon migrating through the five mid-Columbia River reservoirs. By October 1993, all five reservoirs should be indexed for predator populations. The public utility districts should prepare a comprehensive report on the extent of predation and predator indexing in the five mid-Columbia River reservoirs by January 1994. The three mid-Columbia coordinating committees should consult with the Council to determine the need for predator control programs. If the mid-Columbia coordinating committees and the Council jointly determine that predator control programs are warranted, then the public utility districts will implement, monitor and evaluate measures to alleviate juvenile salmonid predation in the appropriate reaches of the five mid-Columbia reservoirs beginning in June 1994.