Lake Washington Basin Predatory Fish Species Suppression: Legislative Proviso Report

Proviso Language The 2023 operating budget (SB 5147, Sec. 308(35), pg. 432) stated: (35)(a) $400,000 of the general fund—state appropriation for fiscal year 2024 and $300,000 of the general fund—state appropriation for fiscal year 2025 are provided solely to initiate a demonstration project to contribute to rebuilding of salmon runs in the Lake Washington basin through suppression of predatory fish species. The project shall include: (i) Removal of nonnative species and northern pike minnow using trap, nets, or other means; (ii) Assessment of the benefits of reduced predator abundance on juvenile salmon survival; and (iii) Assessment of the recreational fishing rules that were implemented in 2020 in the Lake Washington basin. (b) An interim report on the demonstration project must be provided to the appropriate committees of the legislature by December 1, 2024.

This document serves as the interim report for the first year of project work associated with the Lake Washington Predatory Fish Species Suppression proviso (Lake Washington Proviso) conducted in the 2023-24 fiscal year. All planning and spending during the first year of the Lake Washington Proviso project was done with the idea that $400k was available for use in the 2023-24 fiscal year.

Following an initial year of funding at the $700K/biennium level the Lake Washington Proviso funding was increased in the second year to $1.4M/biennium in the 2024 operating budget, with the revised language reading as follows: (35)(a) $700,000 of the general fund—state appropriation for fiscal year 2024 and $700,000 of the general fund—state appropriation for fiscal year 2025 are provided solely to initiate a demonstration project to contribute to rebuilding of salmon runs in the Lake Washington basin through suppression of predatory fish species. The project shall include: (i) Removal of nonnative species and northern pike minnow using trap, nets, or other means; (ii) Assessment of the benefits of reduced predator abundance on juvenile salmon survival; and (iii) Assessment of the recreational fishing rules that were implemented in 2020 in the Lake Washington basin. (b) An interim report on the demonstration project must be provided to the appropriate committees of the legislature by December 1, 2024.

History

Lake Washington is in the heart of an urban area of King County and Chinook, coho, and sockeye are well known, highly visible salmon species inhabiting the watershed. Chinook and particularly sockeye salmon returns to the Lake Washington watershed and the Cedar River have experienced precipitous declines in recent years and the Cedar River sockeye population is currently in a state of crisis. Research and monitoring conducted over the past decade in Lake Washington indicates that predation by non-native fish species and northern pike minnow is limiting survival for juvenile salmon. Climate change and continued illegal introductions of predator fish such as walleye and northern pike exacerbate the predation problem. Poor salmon returns in this highly populated watershed disproportionately affects under-served communities and Native American tribes. One management action that has been proposed to help recover sockeye and Chinook in Lake Washington is a program to reduce the abundance of piscivorous fish species, including all nonnative predator fish species and northern pike minnow, that prey on juvenile salmon rearing in the Lake. Hydroacoustic monitoring of juvenile Chinook and sockeye outmigration via sonar deployment provides a critical validation tool for determining success of predator removal.

First-year implementation of the demonstration project involved deployment of nets in Lake Washington to locate and remove predator fish species during the time that juvenile Chinook and sockeye salmon are rearing and migrating in the watershed. The project approach was informed by previous monitoring and research efforts that have identified areas of the Lake Washington watershed where non-native piscivorous fish species such as northern pike, walleye, yellow perch, bass, black crappie, and northern pike minnow consume juvenile Chinook and sockeye during the Lake-rearing and out-migration periods. Suppression of predatory fish species is intended to increase survival for Chinook and sockeye salmon, leading to increased adult returns and fishing opportunities for these species in Lake Washington. To assess the success of efforts to suppress predatory fish species, a juvenile salmonid hydroacoustic monitoring effort is underway to assess the abundance of outmigrating smolts. Using this technology in conjunction with supplemental juvenile PIT tagging efforts, this project aims to quantify survival trends of juvenile salmonids through the Lake Washington Ship Canal.

Nearly 2.5 million people live in King County where the Lake Washington watershed is located and more than 1 million of those people reside in cities directly adjoining Lake Washington itself (Seattle, Bellevue, Renton, Rainier City, Kirkland, etc.). The Lake Washington demonstration project, if successful, would benefit millions of people. Increased returns of adult salmon would result in direct and indirect benefits to all local residents and the many diverse communities located in the Seattle area.