Influence
of temperature on Chinook salmon survival and abundance across the
species range.
Currently,
I am comparing likely direct effects of future temperature patterns on
Chinook
salmon across their latitudinal range. In
collaboration with Mary Ruckelshaus and Tim Beechie of NOAA Fisheries
and
several others in a working group, I have developed a mechanistic
lifecycle model
predicting effects of peak temperatures on survival during Chinook egg,
juvenile,
and adult lifestages. Collaborators at
the University of Washington Climate Impacts
Group of and University
of Montana NTSG
provided a large scale hydrological model estimating
historical and future
river temperatures at the 1/16th degree
resolution under two global
climate model scenarios.
Focal
watersheds were identified at interior
river basins in the Sacramento, upper Columbia, lower Thompson, and
Yukon
rivers where adult
escapement, harvest,
age structure, and juvenile abundance data were available. Traditional stock
recruitment methods were used
to estimate contemporary productivity rates. Chinook
salmon have optimized run timing to make
use of freshwater habitats within their temperature limits. From the
northern
to southern edge of their distribution, we identified case studies
reflecting
recent impacts of high temperatures. This has allowed
us to synthesize species level
functional relationships between temperature and survival, and to
forecast
survival and abundance patterns at local basins. With the hydrological
model providing
estimates of the historical/future temperature landscape, our
assessment of
current population dynamics allowed us to evaluate likely future
effects of
temperature on freshwater productivity rates, assuming community
interactions
and other factors remain constant.
Incubation
temperatures during fall and winter may be a strong factor determining
spawning
habitat for some populations, resulting in optimal emergence timing for
growth
in the spring. Using Columbia river region hydrological data inputs, we
are
exploring seasonal thermal patterns in habitat preferred by early runs
of
Chinook salmon under a simple growth model, and are trying to identify
the
relative significance of peak
summer
temperature restrictions vs.
selection
for optimal emergence timing.
Sympatric speciation, and population genetics of high
dispersal species
I conducted
a phylogeographic study with widow, black and
blue rockfish (Sebastes),
with two years of adult and
juvenile cohort samples in collaboration with Libby Gilbert, Carlos
Garza, . In this effort, we attempted to resolve the
significance of species-specific behaviors in determining mean lifetime
alongshore dispersal among species sharing spawning season and adult
habitat. Secondly, we addressed the importance of contrasting
circulation patterns in central California vs. northern California and
Oregon on rates of alongshore dispersal. Among all species, nearly
panmictic levels of gene flow were observed over 850km distances.
A surprising outcome of using high resolution nuclear genetic markers
for this study (14-17 microsatellites) was the observation of
two
morphologically-similar subspecies among the previously recognized
single species of blue rockfish (Sebastes
mystinus). The two groups of blue rockfish are
reproductively isolated, and
have developed a moderate level of genetic differentiation
equivalent
to several other discrete, but closely related Sebastes
species pairs. The two species are sympatrically distributed
over
several hundred kilometers of overlapping range, and the low level of
gene flow implies that behavior plays a major role in
decreasing
hybridization and maintaining isolation.Sampling efforts
are underway to learn the distribution, mechanism of reproductive
isolation, ecological habitat associations, and length-at-age
relationships of both species for stock assessment purposes.
Cryptic Blue rockfish -
A new species discovery? NOAA statisticians
involved in
stock assessments routinely interview fishers to verify and groundtruth
collected data. One on our team found that several boat
operators
in the area of Crescent City, CA ( Bruce Miller ) have long recognized
two color morphs of blue rockfish with a list of correlated traits.
While most morphological types in nature result from simple
color
polymorphisms rather than reproductive isolation, the credit for
species discovery probably should be credited to traditional
knowledge of fishers of this highly abundant speices. In the field, it
can be challenging to identify these cryptic types.
Ecological
applications of physical ocean models
With
an applied fisheries perspective, I developed a Matlab toolbox for
processing lagrangian floats data from a 3-D coastal ocean model (ROMS)
in collaboration with Chris Edwards of UC Santa Cruz. In a central
California implementation of this model, we measured the effect of
coastline topographical features on mesoscale movement of drifters
which could be assigned to display simple behaviors and
seasonality. Assessment of interannual variation and
seasonality
was conducted with COAMPS wind field forcing over 1999-2004.
In collaboration with Steve
Ralston, qualitative and statistical
comparisons were made with a dataset of larval rockfish fish, krill and
phytoplankton sampled interannually by NOAA Fisheries within the
central and northern California region.
Effect of cross-shelf position on retention, and expected distributions
of alongshore dispersal outcomes was assessed for floats either fixed
at several isobaric depths or permitted to move vertically. We
have designed many aspects of this model to
be relevant to evaluation of scale and seasonality of
drift
movement, connectivity between subregions,
the marine reserve performance monitoring that my collaborators are
directly
involved in Marine
Protected Area (MPA) performance,
Examples:
Destination after 30 days (note - Quicktime required to
view animation files)
This
shows a series of ROMS (Regional ocean modeling system) simulations in
central California, restarted one month apart during the year 2002, and
each lasting for 30 days duration. Floats at 5m depth are color coded
by their position after 30 days. This is done in order to show the
start region of floats which are retained over the shelf, which could
be considered analogous to successfully settling marine larvae. Yellow
indicates floats further than 60km from shore, and red, green and blue
are 0-20km, 20-40km, and 40-60km respectively. The running date is
indicated in the title. The compass arrow shows the wind direction and
magnitude at Monterey Bay buoy.
Exiting
north/south/offshore border by 1 month
Here,
simulations are each restarted one week apart during the year 2002,
with each lasting for 30 days duration. Floats at 5m depth are color
coded by the border they will hit by before one month (northern - blue,
southern - red, offshore - green), or those retained within the model
domain (black). Apologies - the fraction of floats in each exiting
category is printed in the legend, however the text is difficult to
read in this reduced size version-focusing on the colors will provide
most of the experience.
My doctoral work was carried out in the lab of Zack Powell. This
entailed field sampling of range and abundance, phylogeographic and
population analysis of two species of introduced and native estuary mud
crabs. To explore the feasibility of nonanthropogenic coastal dispersal
by invasive estuary organisms, I developed an oceanographic model of
alongshore transport in the NE Pacific, with a statistical examination
of factors contributing to asymmetrical directionality of larval
dispersal as well as temporal patterns of episodes of long-distance
dispersal.
In
collaboration with Carol E. Lee, I carried out several physiological
studies related to the repeated evolution of freshwater tolerance by
the copepod Eurytemora
affinis
