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Columbia Basin Fish and Wildlife Program Columbia Basin Fish and Wildlife Program

Assessment Summary

ISRP Assessment 1995-009-00-ISRP-20060831
Assessment Number: 1995-009-00-ISRP-20060831
Project: 1995-009-00 - Lake Roosevelt Rainbow Trout Net Pens
Review: FY07-09 Solicitation Review
Completed Date: 8/31/2006
Final Round ISRP Date: None
Final Round ISRP Rating: Meets Scientific Review Criteria
Final Round ISRP Comment:
This popular program, supported by dedicated volunteers, appears fundable at the increased release level of about 750,000 rainbow trout per year, as was proposed. The response provided evidence and logic to indicate that the proposed expansion of the program would have minimal impact on hatchery and wild kokanee by way of increased predation by rainbow trout.

In the future, the proposal should place some additional emphasis in reporting the estimated harvest (number, or percentage, of the fish released from netpens that are caught and those kept by anglers). Those data should be gathered regularly through the Fisheries Evaluation Program. As project personnel are aware, a successful netpen project will be one that, among other things, returns a good percentage of fish to the angler, not just into the lake.

Reviewers applaud the decision to move into 100% triploid rainbow trout releases beginning after 2007. The ISRP recommends that only female triploids be stocked, because male triploids (in mixed sex production lots) will engage in courtship behavior with native trout, possibly leading to gamete waste (from the native trout). The ISRP notes that standardized Quality Assurance/Quality Control protocols are not yet established for using sterile female triploids to provide recreational angling in waters inhabited by native trout. Large-scale production of triploid female rainbow trout is not 100% effective. Sponsors should have the production lots they stock evaluated for the percentage of triploids, and report this as part of the project monitoring. The efficacy of avoiding hybridization between stocked and native trout is unknown when less than 100% of the stocked fish are triploids. Ongoing evaluation of hybridization in contemporaneous native trout populations will be needed in the future. Stocking triploid females to provide recreational angling in regions with highly sensitive native populations is not yet justified. See Kozfkay, J. R., J. C. Dillon, and D. J. Schill. 2006. Routine use of sterile fish in salmonid sport fisheries: are we there yet? Fisheries 31(8):392 - 401.
Documentation Links:
Proponent Response: