An Evaluation of Steelhead Habitat and Population in the Gabilan Creek Watershed Julie Hager Capstone Project 5/24/01 State Water Resource Control Board

Primary Objectives vIs there suitable habitat for steelhead in the Gabilan Creek watershed? vHave populations existed there in the past? vDo populations currently exist, and if not, why?

Overview vSteelhead life cycle and characteristics vReconnaissance survey vSpawning and rearing habitat vPopulation survey

Limiting Factors Temperature (Preferred ° C) Dissolved Oxygen (Criterion >7.8 mg/L) Suspended Sediment (Criterion <25 mg/L) Cover (overhead and escape) Food (aquatic insects) Lack of Pools and Sufficient Flow Migration Barriers Substrate for Spawning (diameter cm) Pollution Overfishing

Gabilan Creek Watershed Reach 1 Reach 2 Reach 3

Phase 1: Reconnaissance Survey v perennial water vobstructions v creek pattern, profile, and roughness vimportant features: pool/riffle sequences dominant substrate bank condition riparian vegetation pollution sources adjacent land use fish and frog sightings estimates of bankfull width and depth

Reach 1

Reach 2

Reach 3

Phase 2: Detailed Habitat Assessment Rearing Index for Young-of-Year length, width,& depth velocity & embeddedness rate cover and roughness # fish per meter suspended sediment, DO, & temperature

Monitoring Above Preferred Range Can Prevent Migration

Phase 3: Population Assessment vElectrofishing was not conducted due to lengthy ‘take’ permit process vDuring ~400 visits, zero steelhead were observed vLocal residents reported 20 inch steelhead catch ~10 years ago

Is there suitable habitat for steelhead in the Gabilan Creek Watershed? vSuitable rearing and spawning habitat exists in the headwaters vWatershed has potential to support 30,000 young-of-the-year vReclamation Ditch and lower reaches are problematic for migration: lack sufficient cover lack woody debris uniform flow structure lacking pools and riffles high summer temperatures high suspended sediment concentrations YES

Have populations existed there in the past? Maybe vOne interview reported a catch 10 years ago vzero positive steelhead observations (lack of rainfall and flow) v16 Rainbow Trout were observed in headwaters vpotential exists due to polymorphic life-history allowing resident trout to assume anadromy Do populations of steelhead currently exist? No

Outcomes vPrior to this study, there was no information on steelhead habitat or population in Gabilan Creek vIncrease awareness within management, local agencies, & community about the potential for a steelhead run in Gabilan Creek vAddress problematic areas in the lower reaches (restoration, education, sustainable land use practices) vRDIPAC vContinue studies on steelhead habitat and population in the Gabilan Creek watershed

Acknowledgements Dr. Fred Watson Joel Casagrande Wendi Newman Thor Anderson SSS Team Dr. Lars Pierce Dr. Bob Curry Marc Angelo Dr. Doug Smith Scott Hennessey David Dettman Jennifer Nelson Joy Nguyen Cheri Everlove Dave Rosenow SWRCB: