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Spatial variation in the trophic position of freshwater fishes in the Bear River Drainage, Great Basin, Utah. Mason Segura, Jeff Wesner and Mark Belk Department of Biology Brigham Young University. Background. Northern leatherside chub. Upper Bear River (UT, WY), Snake River

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Presentation Transcript
slide1

Spatial variation in the trophic position of freshwater fishes in the Bear River Drainage, Great Basin, Utah

Mason Segura, Jeff Wesner and Mark Belk

Department of Biology

Brigham Young University

background

Background

Northern leatherside chub

Upper Bear River (UT, WY), Snake River

Threatened species

Described in 2004

Need ecological information for management and recovery

background1

Background

Northern leatherside chub

2010/11 - Factors affecting abundance

2010/11 - Factors affecting occurrence

some sites have good habitat but no leathersides

Some sites have good habitat, but no leathersides

Leath. absent

Leath. present

2010/11 - Factors affecting abundance

2010/11 - Factors affecting occurrence

Current - Factors affecting food webs (trophic position, food chain length)

slide5

Does trophic level vary across sites?

  • Are trophic positions of common species different at sites with/without northern leatherside chub?

Redside shiner

Northern leatherside chub

Similar habitat requirements

Similar life-histories

Similar foraging strategies

Similar isotopic niches

Positive co-occurrence and abundance

REDSIDE IS COMMON, LEATHERSIDE IS RARE

slide6

N

Bear River

stable isotope analysis

Stable isotope analysis

  • 14 sites
  • 5 species
  • 10-15 individual fin clips per species
  • all adults
  • algae, aquatic insects, terrestrial insects, terrestrial plants
  • Analyzed stable isotopes of C14 and N15
stable isotope analysis1

Stable isotope analysis

  • 14 sites (9 analyzed so far)
  • 5 species
  • 10-15 individual fin clips per species
  • all adults
  • algae, aquatic insects, terrestrial insects, terrestrial plants
  • Analyzed stable isotopes of C14 and N15
stable isotope analysis5

Estimate trophic position relative to algal baseline

Increase of 3.4 δ15N = 1 trophic level

Stable isotope analysis

2° consumer

2° consumer

1° consumer

1° consumer

1° producer

1° producer

trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

Trophic position of fishes varies across sites

1° consumer

1° producer

slide14

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer

slide15

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer

slide16

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer

slide17

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer

slide18

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

x

x

x

x

1° producer

slide22

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

1° producer

slide23

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

1° producer

slide24

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer

slide25

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer

theory explaining food chain length

Ecosystem productivity

Ecosystem size

Theory explaining food chain length

Food Chain Length

Disturbance

McHugh et al. EcolLett 2010

theory explaining food chain length1

Ecosystem productivity

Ecosystem size

Theory explaining food chain length

Food Chain Length

Disturbance

McHugh et al. EcolLett 2010

theory explaining food chain length2

Ecosystem productivity

Ecosystem size

Theory explaining food chain length

Food Chain Length

Disturbance

McHugh et al. EcolLett 2010

food webs

fish

fish

predatory insects

Changes in trophic level can indicate disturbance

Food Chain Length

Food webs

herbivorous insects

herbivorous insects

Algae

Algae

Competitive exclusion of leathersides by redsides in disturbed, simplified systems?

Disturbance

Food Chain Length

Disturbance

McHugh et al. Ecol. Lett. 2010

slide31

Intermediate predators occur at leatherside sites

(but not quantitative samples)

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer

preliminary conclusions

Trophic position of fishes is higher at sites containing northern leatherside chub.

Not explained by differences in habitat.

Not explained by ecosystem size.

Potentially explained by loss in intermediate trophic level, caused by disturbance.

Preliminary conclusions

slide33

Acknowledgements

Luke Schultz and crew

Craig Amadio

Jason Luginbill

Dave Zafft

Pete Cavalli

John Henderson

Annie Hancock

Brian Hale

Allystair Jones

Kayla Melling

Sage Kelley

Brent Hutchinson

Peter Meyers

Ryan Quinton

Eric Mattson

Eric Billman

Matt Terry

Ali Tippetts

Funding and permits

- Bureau of Land Management

- Utah Department of Natural Resources

- Wyoming Game and Fish

is algae a good baseline

Is algae a good baseline?

Mountain sucker

r2 = 0.73, p = 0.0308

Redside shiner

r2 = 0.56, p = 0.0206

YES

Speckled dace

r2 = 0.55, p = 0.0216

Aquatic insects

r2 = 0.67, p = 0.0067

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