Bull trout population assessment and life history characteristics

Bull trout population assessment and life history characteristics in association with habitat quality and land use: a template for recovery planning • Phaedra Budy Utah Cooperative Fish & Wildlife Research Unit • Howard Schaller • Jeff Kershner

Overall Project Goals • Population abundance, density, and growth – – – Juvenile (sub-adult) Adults Life-stage specific survival rates Movement Annual rates of population change • Relationships between populations and survival versus habitat quality and land use • Develop analytical tools for USFWS recovery planning and prioritize areas for habitat improvement

Imnaha Subbasin • Proposed Sites – Imnaha mainstem – Lick Creek – Big Sheep Creek • Sites were chosen based on: – Need for basic population data for recovery planning – Contrast in habitat quality – At least some present or historical data available – Subbasin contrast (Imnaha vs. Little Salmon)

Bull trout in the Imnaha • Migratory and resident forms • Population size unknown • Some data: – Intermittent redd counts (USFS) – Presence/absence surveys – Isolated and limited trapping and snorkel surveys – Radiotelemetry

Study Design 1. Comprehensive population assessment: • Marking – PIT and floy tags • Recapture – electroshocking, seining, screw traps, snorkeling (resighting), and trapping: • • • Big Sheep Creek Weirs Screw traps at confluences Pass-through PIT tag antennae Little Sheep Creek North Fork South Fork Lick Creek Imnaha River Snake River

Study Design 2. Comprehensive population assessment (cont. ) : • Snorkel surveys – juvenile and adult abundance and density estimate • Adult spawner and/or redd counts • Fecundity, sex ratio, and age -- borrow from literature, sample scales for age

Study Design 3. Stream and riparian habitat assessment (USFS): Land use and current management (e. g. , road density or culvert failure rate) Riparian / floodplain and habitat (e. g. , fragmentation of riparian vegetation) In channel and community integrity (e. g. , water temperature, sediment)

Expected Results • Population abundance form M/R (+/-) and snorkel: • • Resident adults Migratory adults (trapping and redd counts) Juveniles Life-stage specific survival rates (e. g. , egg-to-parr survival) • Movement among streams and subpopulations • Habitat use and preference (broad scale and micro-habitat)

Expected Results (cont. ) • Annual rates of Population Change (lambda) • Pradel M/R model • Lambda = f { apparent (recruitment – survival)} • Simple life-cycle model: • • • predict annual rates of population change (lambda) to monitor trends response variable

Expected Results (cont. ) • Relationships between habitat quality and land use & bull trout survival and abundance • • • Broad Scale – USFS sites as index of bull trout habitat, prioritizing streams etc… Local habitat preference and limiting factors S Eggs S Fry S S Parr Subad S S X X X

Evaluate feasibility of passthrough PIT-tag technology • Larger PIT tags (23 mm) • Cost Effective Passive hoop detection • Backpack-wand mobile detection • Feasibility check --2002 in smaller streams , 2 -3 sites per stream, near headwaters and at confluences • Provides: • • • Recaptures Movement Microhabitat use

Needs and Limiting Factors • For bull trout management and recovery planning: – Basic population abundance data • Evaluate population status • Monitor population trends and effectiveness of management actions – Information about the relationship between habitat quality and population abundance • Understand how habitat affects bull trout survival and movement • Identify and prioritize core areas for habitat improvement – Analytical tools and information on population attributes for bull trout planning • other areas where data are lacking – Cost effective methods for monitoring and evaluation