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200102800 - Banks Lake Fishery Evaluation Project

Sponsor: Washington Department of Fish and Wildlife (WDFW)

Budgets: FY07: $482,076 | FY08: $609,631 | FY09: $471,756

Short description: The Banks Lake Fishery Evaluation Project proposes to enter an implementation phase, applying results from the past 4 years to create strategies to maximize kokanee production in the lake with the creation of an artificial spawning channel.

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Final Council recommendation (Nov 2006)

Funding category: Expense

Recommended budgets: FY07: $0 | FY08: $0 | FY09: $0

Comment: Include project in review of kokanee projects through kokanee workshop. Funding to be identified and contingent on outcome of workshop. Consider moving the project to the Intermountain province.

ISRP final recommendation: Fundable in part


The non-fundable element is the proposal to create a spawning channel for kokanee (withdrawn by sponsor in their response). The ISRP has serious misgivings about the project’s emphasis on creating a kokanee fishery by other means, as well, because significant populations of non-native, top-predator fishes exist in the lake. However, kokanee stocking could justifiably proceed under appropriate monitoring and evaluation, and in view of the sponsor’s revised proposal to manage angling to reduce the lake’s walleye population. The project involves the problem-prone situation of an artificially created and artificially manipulated water body that contains an artificial assemblage of fishes, including species not native to the region. The lake functions in some unnatural ways to which the fish are not adapted, and some members of the fish assemblage are not adapted to interact well with each other. The sponsors' task of trying to manage this system to suit a diversity of angling interests is difficult indeed. The project’s stated purpose is fishery mitigation for the loss of anadromous salmon. The proposal's main focus is on creating a kokanee fishery, secondarily rainbow trout, walleye, and bass. Its more specific goals involve increasing natural-origin kokanee (thus reducing fishery reliance on hatchery-origin kokanee), while maintaining “quality fisheries” for walleye, bass, and burbot. Toward this, and based on the project’s previous studies, the sponsors proposed two lines of work: (1) to continue studying water quality, food limitation, angling exploitation, predation by exotic fishes, and the effectiveness of hatchery kokanee releases (adaptive management implied) and (2) to increase the lake’s kokanee production by enhancing spawning habitat and improving access at Northrup Creek and adjacent shorelines. The ISRP considered the idea of trying to boost kokanee production by creating an artificial spawning channel unsound, partly because a concentrated source of kokanee fry could attract walleye to the entry area, and thus much of the new production would just feed predators. In response, the sponsors withdrew that part of the proposal. Moreover, the ISRP considered the original proposal's overall emphasis on kokanee scientifically unsound and thus not fundable because the sponsor maintains major fisheries for walleye and bass in the lake, and these are top predator species capable of preying on kokanee. The proposal indicated that the project’s studies to date found predation by walleye to be a limiting factor for kokanee in the lake. The narrative stated: "Predation has been identified as the predominate factor affecting survival of kokanee in Banks Lake. Annual kokanee losses to walleye predation are 13-17% . . . a conservative estimate since acute predation occurs during stocking events." Also, the proposal stated that smallmouth bass are about three times more abundant than walleye but did not mention their effects on kokanee. The ISRP suggested that the effort to manage for a significant kokanee fishery in the lake halt, pending literature evidence from elsewhere that suggests kokanee can thrive in the face of predation by walleye and bass, species with which kokanee did not co-evolve. The ISRP suggested also that the sponsors should clearly eliminate alternative hypotheses for low numbers of kokanee before accepting the alternative that shortage of spawning habitat is the problem. The ISRP recognized that a strategy of eliminating walleye and bass from the lake probably would be impractical from a management standpoint and undesirable for many of the lake’s present anglers. The ISRP rated the proposal as not fundable and explained that it did not request a response because the proposal presented enough information to determine, based on science, that the management strategy described had a very low probability of success. In other words, the project did not meet criteria for benefit to fish and wildlife. The sponsors submitted a reasonably thorough response that showed thoughtful consideration of the issues. They dropped the idea of a kokanee spawning channel, but maintained that continued emphasis and study of kokanee stocking should continue. They argued, somewhat in contradiction to statements in the original proposal, that predation on kokanee by walleye is not great enough to impair the development of a viable kokanee population and fishery. They held that bass predation must be insignificant. They offered other evidence (mainly gray literature and personal communications) to support those positions, pointed to recent improvement in kokanee catch (probably due to changed stocking procedures), and said they could liberalize angling regulations so as to reduce the walleye population. Regarding bass predation, they contend that bass occupy shallow areas that do not overlap significantly with salmonid habitat of the same lake, that bass would not eat many salmonids, and that kokanee exist in other Washington lakes that contain bass. On the other hand, the ISRP is aware of evidence that bass eat many rainbow trout in some California lakes. Furthermore, the sponsors have not yet truly measured predation by walleye and bass in Banks Lake. A related problem is that the sponsors can express the fish populations only in terms of relative size (percentage of total species composition) and do not know their numerical abundances. This is understandable in a large body of water that is difficult to sample for abundance estimates. The ISRP recommended that the sponsors search literature for evidence that kokanee are compatible with walleye and bass. In an intensive search for this, the sponsors found little: the only reports on waters containing all three species together came from Lakes Roosevelt and Rufus Woods, where harvest and escapement goals for hatchery kokanee have not been achieved. The sponsors feel those situations do not apply to Banks Lake. The response stated: “We can find no literature to support [the ISRP] conclusion that these species [kokanee, walleye, smallmouth bass] are not compatible . . .” This isn’t surprising, for kokanee, a Pacific drainage species, did not coevolve with those Atlantic drainage species. There is, however, reason to expect low success in trying to maintain a kokanee fishery in the face of walleye and bass populations because kokanee are unlikely to be well adapted for coexistence with those predators. The ISRP still has serious concern about the advisability of trying to manage for kokanee in a walleye and bass lake but believes the project could be funded in part to continue testing that effort.

Response loop edit

See the sponsor's revised proposal from the response loop. You'll be taken to CBFWA's proposal system in Section 10 where most sponsors uploaded revised narratives or other responses to the ISRP comments.

State/province recommendation: Washington

Review group: Washington list

Recommended budgets: FY07: (n/a) | FY08: (n/a) | FY09: (n/a)

Comment: See Washington guidance