How To S urvive A D rought - PowerPoint Presentation

Slide1

How To Survive A Drought

The bioenergetic efficiency of juvenile Chinook salmon feeding strategies during a drought in the San Joaquin River, CaliforniaTaylor Spaulding

Justin Sullivan/Getty Images

John Walker — Fresno Bee Staff PhotoSlide2

OutlineProblem

MechanismQuestionOrganismHypothesis and Predictions

VariablesMain Factors

Main Effects

ConsiderationsExperimental Design & Sampling

HabitatPrey

Salmon

Modeling

Statistics and TestingInterpretation and DeliverablesSlide3

ProblemMechanism

Salmonids can employ two different strategies when feeding, Drift (A) and Benthic (B) foragingDrift = ambush

Usually more efficient, allowing energy to be conserved and net energy intake optimizedBenthic = searching

Usually, less efficient, requires actively swimming and searchingSlide4

Bioenergetic

modeling of salmon only includes drift foraging; assumed to always be more efficientEfficiency of drift foraging is dependent on many factors:TemperatureTurbidity

VelocityPrey availability and qualityInfluenced by velocity

Predation riskC

ompetitive exclusionDrought conditions in rivers may lessen the efficiency of drift foraging

Increased temperaturesDecreased prey availability/quality

Increased competition and predation risk due to habitat loss

Problem

MechanismSlide5

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

QuestionSlide6

Chinook Salmon (Onchorhyncus tschawytschaRear 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

OrganismSlide7

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

.

HA1: 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 populationSlide8

Variables

Main Factors affecting foraging efficiencyWater 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 efficiencyIncreased rates of growthConsiderations

Habitat characteristics (vegetation, substrate, temperature, and water velocity) can affect prey assemblagesSlide9

Experimental Design & SamplingHabitat

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

o

xygenSlide10

Experimental Design & SamplingPrey

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 OrderSlide11

Experimental Design & SamplingSalmon

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 calculationSlide12

Experimental Design & SamplingModeling

Stable Isotope Modeling

Modeling of diet using ratios of

δ13C & δ15N found in salmon liver tissue and invertebrate whole tissue.

Liver resolution is ~ 1 weekMixed 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)Slide13

Experimental Design & SamplingModeling

Bioenergetics/Population Modeling

Using

inSTREAM, a model of whole populations with a focus on individuals

Developed by Steve Railsback and Brett HarveyComponents

Water velocity, depths, and refugia derived from hydrological modelsTemperatureTurbidity

Prey Quality and Quantity (Both benthic and Drifting)

Output

Daily and average growth rates for each individual within the populationSlide14

Testing & Statistics

Output from

bioenergetic model is growth rate which is directly comparable to growth rates derived from Otolith

analysesGrowth Rates from models or observations to testDrift

Drift + BenthicObservedMean TestingH0

testable using ANOVADunnet’s test would be an excellent post-hoc test, setting the observed growth means as the controlOther mean testing operations may be available

Residual Testing

Testing the residuals of the models to determine how well it fits the observed dataSlide15

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

*Slide16

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. Slide17

Questions?