Review of Expanded Proposal for Lake Roosevelt Northern Pike Suppression Project (1994-043-00)

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At the Northwest Power and Conservation Council’s June 2, 2017 request, the ISRP reviewed a proposal from the Spokane Tribe of Indians (STOI) to increase and expand northern pike removal efforts in Lake Roosevelt as part of Project #1994-043-00, Lake Roosevelt Data Collection. Specifically, the project proponents propose to prevent further establishment and geographic spread of northern pike within and downstream of Lake Roosevelt by reducing northern pike abundance in the Kettle Falls area. In their proposal, the proponents explain the need for an expanded removal effort: “The Lake Roosevelt Northern Pike population is experiencing chronic recruitment and exponential growth. Since the initial 2015 pilot study, the Lake Roosevelt Co-Managers have removed over 2,000 Northern Pike in the Kettle Falls area, encountered an increasingly diverse size-class structure, and documented the presence of age-0 Northern Pike in the Kettle River, Colville River.”

The ISRP had previously reviewed a 2016 proposal for a pilot removal effort (ISRP 2016-6) and recommended the project met scientific review with qualifications. The Council considered the ISRP’s review and recommended implementation of the project through 2018 with the condition that the ISRP’s qualifications be addressed in contracting and that funding beyond the Fiscal Year 2018 field season will depend on ISRP and Council review. In the 2016 proposal, the proponents stated it is critical that a monitoring and suppression plan be developed immediately while abundance is still relatively low… to reduce the risk of Northern Pike numbers expanding within Lake Roosevelt and beyond.”

ISRP recommendation for the 2017 expanded effort: Meets Scientific Review Criteria (Qualified)

The STOI proposal partially meets scientific criteria by providing evidence that the northern pike population is now reproducing and spreading in Lake Roosevelt. Northern pike are likely to have a significant effect on native fishes, including anadromous salmonids, if their distribution expands further downstream from Lake Roosevelt. The ISRP is not surprised that further suppression efforts are needed, as we had previously questioned (ISRP 2016-6) whether the current removal effort would be sufficient to control the spread of northern pike in Lake Roosevelt. Even though the quantitative catch per unit effort (CPUE) data from standardized surveys presented in the proposal for 2015-2017 do not demonstrate a substantial increase in the northern pike population, other information regarding abundance and age distribution of catches in recent sampling efforts suggests that additional suppression is warranted.

Other aspects of the proposal fall short of expectations. Most of the previous ISRP qualifications have not been adequately addressed. The description of objectives is improved but still not adequate. Objective 1 for suppressing northern pike is stated quantitatively, but the 5-year timeline for achieving this objective does not match the 1-year time frame of this proposal. Objective 2 identifies catch limits for non-target species but it does not specify limits per unit time or unit of fishing effort, and it includes limits for non-native piscivores. Objective 3 describes a method for gillnetting rather than an expected outcome quantified with a timeline to track progress.

Thus, the following concerns, along with our original qualifications (see Part B below), must be addressed. The responses to the qualifications and concerns should be described in the next annual report and also in the Three-year Northern Pike Relative Abundance Survey and Suppression Plan. The ISRP should review the annual report and the Suppression Plan before long-term commitments are made for this project.

  1. Provide quantitative objectives and timelines, as discussed below and in ISRP 2016-6. Clearly articulate quantitative catch limits for non-target species.
  2. Provide justification for terminating the suppression of northern pike if catch limits are exceeded for non-native walleye and smallmouth bass and hatchery trout.
  3. Describe in more detail the methodology and level of effort associated with the proposed expansion of the removal effort, and demonstrate how the methodology will be adequate to track the status of northern pike in Lake Roosevelt over time.
  4. Assess whether the benefits of longer nighttime set times outweigh the harm to other species by comparing catch rates of northern pike and mortality rates of other species in daylight versus nighttime sets, and using gillnets versus electrofishing.

In summary, the ISRP recommends that the current proposal sufficiently meets scientific criteria to begin expansion of efforts to suppress the spread of northern pike in Lake Roosevelt, provided the proponents can at the same time meet the urgent qualifications listed above, with emphasis on developing and implementing a monitoring program. However, the ISRP cautions that much more analysis and policy development is needed to justify a long-term program to suppress northern pike in Lake Roosevelt. Indeed, the overall strategy for controlling northern pike and other non-native predators requires broader discussion within the Fish and Wildlife Program.