WDFW lunchtime seminar series presents:
****** Bob Vadas, WDFW Habitat Program ******
“Long-term population response of Coastal Cutthroat Trout to environmental
fluctuations in a temperate-rainforest stream: hydrology, temperature, and
invasive weeds and other biotic factors”
Monday, December 17, 12:00 – 1:00 pm
NRB 172 and anywhere there you have internet via Skype
Talk overview:
In well-forested Irely Creek within Olympic National Park, adfluvial Coastal
Cutthroat Trout (CCT = Oncorhynchus clarkii clarkii) coexists with anadromous
Coho Salmon (O. kisutch) and two resident-fish species. Each spring during
2001-2012, we counted trout redds in mainstem and tributary habitats there,
finding a statistically significant relationship between redd counts and the
previous year’s minimum level for downstream Irely Lake, where all or most
adults rear to adulthood. Run-size estimates (twice the redd count) were
highest (at viable levels) during the first two years, but escapement has since
declined by an order of magnitude, reflecting more-frequent (including
consecutive-year) lake dry-outs along with expansion of exotic reed canarygrass
(Phalaris arundinacea) in the lake. Indeed, wet years elicited incomplete
CCT-run recovery, as resultant population increases were weaker than population
drops from lake dry-outs. Multivariable-statistical analyses for this ‘natural
experiment’ showed complications from time lags, so preceding (last) year
freshwater conditions were better correlated with trout-run success than
same-year biotic and physical conditions. In contrast, winter/spring snowpack
and spring/summer precipitation indices were more-weakly related to CCT-run
size, and full water-year precipitation was uncorrelated with trout abundance.
Although surface (non-hyporheic) water in adult habitat was limiting with a
short time delay for this trout, cumulative-year hydrologic indices for lake
level were even better predictors of escapement than were single-year indices.
Complications for biotic parameters were curvilinear responses, likely
reflecting density dependence for the highest trout-escapement year (2002), but
quadratic-regression terms did not improve predictive ability. The
mechanistically valuable variables for our best multiple-regression models
included (a) cross-year conditions for lake level (that assumed moderately good
cutthroat recovery after past dry-outs) and peak-spawning temperatures
(reflecting the trout’s coldwater preferences); and (b) last-year cutthroat
escapement and coho-carcass counts. Hence, both physical and biotic
(stock/trophic) factors appeared to be important for cutthroat productivity, in
negative vs. positive ways, respectively. So our best monotonic-regression
model can realistically predict future trout escapements, based on
environmental changes from natural and human impacts, to be tested with
more-recent (2015-2018) redd-count data collected with the help of volunteers.
If reed canarygrass is contributing to lake dewatering, or at least stagnation
(water-quality) impacts during partial dry-outs, then this emergent weed’s
removal (starting in 2018) should improve lake conditions and thus contribute
to improved trout escapements in future years. Finally, understanding the
population dynamics of a Pacific salmonid with a relatively simple life cycle
like Irely Creek CCT should make ecohydrologic studies of sea-run salmonids
more tractable.
Bob’s bio:
I have received the following degrees: B.A. in zoology/botany (Ohio Wesleyan
University), M.Sc. in stream-fish ecology (University of Maryland), and Ph.D.
on fish instream-flow issues (Virginia Tech). I have since worked for 2
consulting companies in Alberta and have completed 2 postdoctoral projects in
British Columbia and California on fish-habitat and other issues, with
collective focus on riparian and instream-flow impacts to freshwater and
estuarine ecosystems. I have recently worked as a state-agency biologist,
including past estuarine fish-habitat work with the Florida Marine Research
Institute and present fresh/saltwater (especially salmonid) work with WDFW’s
Habitat Program. My focus has been on hydrologic, habitat, and dietary needs of
fishes, using field sampling, statistical analysis, and ecological synthesis.
Formal instream-flow training includes a postgraduate course at Virginia Tech
in stream-hydraulic modeling, USFWS courses on field and modeling techniques
for PHABSIM, and USGS courses on 2-D hydrodynamic modeling and natural-resource
negotiations. My Washington work has included much field work (including
snorkeling) on spawning and rearing habitat use of cutthroat and coho,
laboratory gut analyses on coho and prickly sculpins, some spawning and rearing
habitat work on Chinook salmon and bull trout, and spawning work on pink, chum,
and sockeye salmon, steelhead, lampreys, and suckers. My British Columbia work,
which had a riparian focus, included much field/lab work on habitat and food
use by Chinook, steelhead, mountain whitefish, and various other stream fishes.
I’m also an active member of the South Sound Estuary Association (which runs
the Puget Sound Estuarium) in Olympia, acting as a scientific advisor and
beach-naturalist teacher for salmonids, other fishes, etc. I also enjoy music
and sports, including active roles, and regularly like to express my odd sense
of humor.
For webinar participants—you can join this meeting from any computer that has
internet access!
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Upcoming talks:
January 14—Daniel Donato and Josh Holofsky, DNR, wildfires on the west side of
the Cascades
January 28—Dan Thornton, WSU professor, using remote cameras to evaluate
wildlife habitat use and population parameters in North Cascades
February 11—Stephanie Kuhns, WDFW, citizen science
March 18—Sara Hansen, WDFW, mule deer population monitoring
April 15—PAO, Licensing/Marketing, and Lands Division Team (Cynthia Wilkerson,
Jason Wettstein, Matt Trenda, Shannon Haywood), Lands Showcase Marketing and
Communications Research and Messaging
May 13—John Calambokidis, Cascadia Research, gray whales in N Puget Sound or
ongoing work on humpback whales
June 17—Carissa Bourdon, WDFW, “leave a legacy” type presentation that is
specific to how to organize work before you retire
