Transcript of How To Survive A Drought The bioenergetic efficiency of juvenile Chinook salmon feeding strategies...
- Slide 1
- How To Survive A Drought The bioenergetic efficiency of
juvenile Chinook salmon feeding strategies during a drought in the
San Joaquin River, California Taylor Spaulding Justin
Sullivan/Getty Images John Walker Fresno Bee Staff Photo
- Slide 2
- Outline 1. Problem a. Mechanism b. Question c. Organism 2.
Hypothesis and Predictions 3. Variables a. Main Factors b. Main
Effects c. Considerations 4. Experimental Design & Sampling 1.
Habitat 2. Prey 3. Salmon 4. Modeling 5. Statistics and Testing 6.
Interpretation and Deliverables
- Slide 3
- Problem Mechanism Salmonids can employ two different strategies
when feeding, Drift (A) and Benthic (B) foraging Drift = ambush
Usually more efficient, allowing energy to be conserved and net
energy intake optimized Benthic = searching Usually, less
efficient, requires actively swimming and searching
- Slide 4
- Bioenergetic modeling of salmon only includes drift foraging;
assumed to always be more efficient Efficiency of drift foraging is
dependent on many factors: Temperature Turbidity Velocity Prey
availability and quality Influenced by velocity Predation risk
Competitive exclusion Drought conditions in rivers may lessen the
efficiency of drift foraging Increased temperatures Decreased prey
availability/quality Increased competition and predation risk due
to habitat loss Problem Mechanism
- Slide 5
- Is the inclusion of benthic foraging a more efficient feeding
strategy during drought conditions; optimizing net energy intake?
Are observed patterns of growth in salmon reared during a drought
consistent with estimates produced with models inclusive of both
strategies? Problem Question
- Slide 6
- Chinook Salmon (Onchorhyncus tschawytscha Rear in freshwater
from approximately January until May/June Small, approximately 30mm
to 120mm (~1- ~4.7) Eat invertebrates such as flies (dipterans),
caddisflies (trichopterans), mayflies (ephemeropterans), Mites
(Hydracarina), and Zooplankton (Daphnidae, Amphipoda, Copepoda)
Problem Organism
- Slide 7
- Hypotheses and Predictions H 0.1 : Models of drift feeding
behavior of juvenile Chinook Salmon will not produce significantly
different estimates of growth rates from those observed in nature
or from models which also include benthic feeding. H A1 : Models
that include benthic and drift feeding strategies will produce
growth rate estimates that are significantly greater than growth
rates produced in models of only drift feeding. H A2 : Models that
include benthic and drift feeding will produce growth rate
estimates that are not significantly different from observed growth
rates within the natural population
- Slide 8
- Variables Main Factors affecting foraging efficiency Water
temperature Prey Quality (Metcalfe et. al. 1999) Prey Quantity
(Metcalfe et. al. 1999) Water velocity (Shirvell 1994) Turbidity
(Gregory & Northcote 1993 & DeYoung 2007) Competition
(Nakano 1995) Predation risk (Gregory & Northcote 1993) Habitat
characteristics (cover/refugia) Main Effect of foraging efficiency
Increased rates of growth Considerations Habitat characteristics
(vegetation, substrate, temperature, and water velocity) can affect
prey assemblages
- Slide 9
- Experimental Design & Sampling Habitat FIGURE 3: MAP OF SAN
JOAQUIN RESTORATION AREA FROM SJRRP (2011) SHOWING LOCATIONS OF
STUDY SITES FIGURE 4 SCHEMATIC OF SAMPLING DESIGN. SOLID LINES
DENOTE TRANSECTS DOTS ON TRANSECT 3 REPRESENT NODES FOR SAMPLING OF
WATER VELOCITY AND SUBSTRATE HOLLOW BOXES DENOTE SAMPLING STATIONS
FILLED BOXES REPRESENT RANDOMIZED SAMPLE SITE FOR BENTHIC SAMPLES.
Four 100m study sites spaced along Restoration reaches 1A and 1B
Reaches divided into 10m transects Recorded water velocities,
temperatures, substrate classes, turbidity, and dissolved
oxygen
- Slide 10
- Experimental Design & Sampling Prey Prey collected using a
stratified random sampling of each site Drifting prey gathered with
depth integrated nets Benthic prey collected using kick-nets.
Sorted to Family or lower dependent on Order
- Slide 11
- Experimental Design & Sampling Salmon Wild fish only
Collected in weirs by the Bureau of Reclamation Trap and Haul
effort led by Don Portz Dissected out livers and muscle tissue for
stable isotope analysis (SIA) Dissected out otoliths for growth and
age calculation
- Slide 12
- Experimental Design & Sampling Modeling Stable Isotope
Modeling Modeling of diet using ratios of 13 C & 15 N found in
salmon liver tissue and invertebrate whole tissue. Liver resolution
is ~ 1 week Mixed using MixSIAR a Bayesian model of dietary inputs.
Can use priors to inform the model Output is used to determine prey
quality (preference for each prey item)
- Slide 13
- Experimental Design & Sampling Modeling
Bioenergetics/Population Modeling Using inSTREAM, a model of whole
populations with a focus on individuals Developed by Steve
Railsback and Brett Harvey Components Water velocity, depths, and
refugia derived from hydrological models Temperature Turbidity Prey
Quality and Quantity (Both benthic and Drifting) Output Daily and
average growth rates for each individual within the population
- Slide 14
- Testing & Statistics Output from bioenergetic model is
growth rate which is directly comparable to growth rates derived
from Otolith analyses Growth Rates from models or observations to
test Drift Drift + Benthic Observed Mean Testing H 0 testable using
ANOVA Dunnets test would be an excellent post-hoc test, setting the
observed growth means as the control Other mean testing operations
may be available Residual Testing Testing the residuals of the
models to determine how well it fits the observed data
- Slide 15
- Predicted Results Results should indicate that the growth
experienced by the wild population is more similar to one model
than the other. Testing the residuals will be used to evaluate
model fit If the model fits well, it can be used for future
analyses *Not real data *
- Slide 16
- Future Directions Best fit model can be used with future San
Joaquin River hydrological modeling to better predict salmon growth
and survival in the river Results from study may indicate a lack of
sophistication in current models when used to describe growth under
sub-optimal conditions Results may show that benthic foraging is an
effective foraging method under certain conditions.
- Slide 17
- Questions?