Habitat - Fish Passage Technical Assistance
Date Published: October 2002
Number of Pages: 31
Author(s): Gary Bell, Jason P. Kunz, Susan Cierebiej-Kanzler, Mike Barber and Paul Sekulich
During the past 62 years, the Washington Department of Fish and Wildlife (WDFW) has acquired approximately 808,000 acres of land statewide to benefit fish and wildlife and provide recreational opportunities. Due to the Agency’s and the Public’s increasing interest in factors affecting fish resources, in October 1997, the Habitat Program initiated an inventory of fish passage and water diversion features on all agency-owned and/or managed lands. WDFW’s Salmonid Screening, Habitat Enhancement and Restoration (SSHEAR) Section was assigned this task. The purpose of the inventory is to document and prioritize for correction, all agency-owned fish passage problems including culverts, dams, fishways, lake screens and unscreened or inadequately screened water diversions to ensure compliance with Washington State laws. According to RCW 77.55.060, “All dams or obstructions across or in a stream shall be fitted with a durable and efficient fishway” and RCW 77.55.040 requires that water diversions be fitted with a screen to prevent fish from entering the diversion.
Salmonids of the Pacific Northwest have long been impacted by structures installed in streams incorrectly or with no regard to the salmonid life cycle. Thousands of juvenile salmonids are killed every year when they enter inadequately screened or unscreened water diversions, by mutilation from a pump or being stranded in irrigation canals as the irrigation season comes to a conclusion. Screened water diversions improperly maintained can also impinge salmonids, either killing them directly or carrying them into the diversion system.
Culverts, dams, non-functioning fishways and lake outlet screens also have a very detrimental impact on salmonid populations. When these facilities result in a barrier to fish passage, spawning and rearing habitats become inaccessible. Each year, more of these structures become barriers to fish passage. Watersheds are continually being altered (e.g., development, logging, new roads, etc.), which substantially influences the hydrological dynamics of the watershed. Culverts, fishways, lake outlet screens, and water diversions that were once designed for a defined flow regime, are now incapable of handling the increased flow. Culverts may become velocity barriers and contribute to scouring of huge plunge pools, that in most circumstances result in large outfall drops. Even hydraulic drops less than 0.30 meter (one foot) in height are a potential barrier to adult chum salmon, juvenile salmonids and other fish species. Recent studies have shown that these small hydraulic drops can limit juvenile production by rendering valuable rearing habitat inaccessible.
In cooperation with the Lands Division of the Wildlife Program, SSHEAR staff designed a sampling protocol, database format, and Wildlife Area Scheduling Index for the inventory. To create the scheduling index of Wildlife Areas, a prioritization questionnaire was distributed to Regional Lands Coordinators, Regional Fish Biologists and Wildlife Area Managers. This enabled SSHEAR staff to take advantage of the many years of experience and data accumulated from local and regional WDFW managers.
The questionnaire was designed to prioritize wildlife areas based on four main factors:
- number of known fish passage problems,
- stock status,
- stock mobility, and
- high profile fish passage and water diversion screening issues of public interest.
This prioritized list was then used to guide, along with other management considerations, the sequence that the wildlife areas would be inventoried. After the index was calculated for each area, they were stratified according to the time of year in which the inventory could be accomplished. Eastern areas will be scheduled in the spring and summer months and the western areas will be inventoried in the fall and winter months. The Sunnyside Wildlife Area is the second inventory conducted in the eastern areas.