Distribution and Abundance of Umpqua Chub and Smallmouth Bass in the South Umpqua Basin

Transcription

1 Distribution and Abundance of Umpqua Chub and Smallmouth Bass in the South Umpqua Basin Joe Tomelleri Cory Sipher 1, Casey Baldwin 2, Jim Peterson 3, 1 Bureau of Land Management, Roseburg, OR US Forest Service Tiller Ranger District, Tiller, OR and Paul Scheerer 4 3 USGS Oregon Cooperative Fish and Wildlife Research Unit, 104 Nash Hall, Oregon State University, Corvallis, OR Oregon Department of Fish and Wildlife, Highway 34, Corvallis, Oregon 97333

2 Overview Study objectives Umpqua chub background Potential limiting factors Previous surveys Study design Current distribution Factors affecting occupancy Next steps

3 Study Objectives Pilot study to assess the use of snorkeling to assess trends in Umpqua chub distribution and abundance in S. Umpqua subbasin o Tested the use of N-mixture and multi-state occupancy model with snorkeling data collected in summer 2015

4 Umpqua chub (Oregonichthys kalawatseti)

5 Umpqua chub habitat

6 Co-occurring Native Fishes Largescale sucker

7 Umpqua Chub Background Recognized as new species (Markle et al. 1991) State of Oregon sensitive and BLM Special Status Species Apparent range restriction and abundance decline coincided with expansion of smallmouth bass

8 Potential limiting factors Smallmouth bass o Predation o Competition Climate change (favors SMB?) Estuary salinity (fragmentation)

9 Historical Distribution Tiller

10 Previous chub surveys (snorkeling)

11 Umpqua chub and smallmouth bass snorkel surveys Smallmouth bass Umpqua chub Simon et al. 2008

12 Study design Discussed need to reinitiate Umpqua chub monitoring at 2015 Umpqua Chub Working Group Meeting Describe current distribution in South Umpqua and Cow Creek Model population abundance and multi-state occupancy

13 Survey design 28 sites sampled on consecutive days Snorkel counts on right and left bank (~5 m band on each shore) Same surveyors on consecutive days Estimated abundance using a N-mixture model (based on count data) and described multi-state occupancy of both Umpqua chub and smallmouth bass

14 N-mixture model (Royle 2004) Uses repeated count data which minimizes handling (none with snorkeling) and requires no marking of animals Goal - find estimates of detection probability and average abundance across all sites that will generate results that closely match the field data Assumptions o Population closure between surveys o Spatial distribution (# individuals occurring at each site) follows a prior distribution (e.g. Poisson), which allows the detection probability to vary among sites o Whether or not an animal is detected at a site is a function of the number of individuals at site

15 Umpqua chub abundance

16 Smallmouth bass abundance

17 Multi-state occupancy model Goal- estimate the probability of occupancy (or proportion of sites occupied) for Umpqua chub and smallmouth bass Models both occupancy and detectability parameters 3 States: absent, present, or present and abundant Nondetection = species genuinely absent or present but not detected (imperfect detection) Assumptions: o Target species is never falsely detected at as site when it is absent (no mis-identification) o Site is closed to changes in the state of occupancy (repeated counts closely spaced in time) Can look at changes in occupancy states over time (versus changes in abundance over time) to assess trends in species status

18 Probability of occupancy Probability of abundant state Probability of Detection Occupancy Modeling Umpqua chub Probability of occupancy parameters o Percent aquatic vegetation Probability of detection o Aquatic vegetation Conditional probability of abundant o Cobble substrate, aq. vegetation Percent vegetation Percent vegetation Percent Vegetation P(abund, cobble) P(abund, not cobble)

19 Occupancy Modeling Smallmouth Bass Probability of occupancy parameters o Average depth Conditional probability of abundant o Average depth Probability of detection o Intercept only (p = 0.77) Pr(occupancy) Pr(abundant) Average depth (m)

20 Next Steps Conduct additional repeated surveys (more than 2 site visits) to describe seasonal changes in occupancy o One location had high abundance of Umpqua chub on first two visits but found no Umpqua chub on next two visits one month later Refine habitat occupancy relationships Identify overlapping habitat characteristics of Umpqua chub and smallmouth bass Estimate the power to detect changes in population abundance or occupancy?

21 Habitat management considerations Use modelling results to identify opportunities to improve habitat for Umpqua chub at occupied sites and restore habitat at unoccupied sites o Vegetation o Substrate o Depth Identify whether habitat partitioning occurs o Deep water for bass o Shallow shoals for cyprinids

22 Habitat management considerations Manage stream temperatures through riparian treatments on tributaries (esp. considering potential impacts from climate change) Instream temperature and/or flow modifications through dam releases Construct season migration barriers for smallmouth bass?

23 Acknowledgements Casey Baldwin Paul Scheerer Jim Peterson Steve Clark Jeff McEnroe Jason Wilcox Scott Lightcap Kelli Van Norman USFS field crew Gina Fritzman Joe Otto Lindsey Negherbon

24 Questions??

25 Questions??

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27 Extra slides

28 Umpqua chub Smallmouth bass Detection probability (percent) Population estimate Occupied sites (n = 28) Umpqua chub Smallmouth bass

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31 Abundance estimates Site Umpqua chub Smallmouth bass A Site Umpqua chub Smallmouth bass

32 Simon 2008

33 Umpqua chub abundance

34 Smallmouth bass abundance