Spatial variation in the trophic position of freshwater fishes in the Bear River Drainage,
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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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Mason Segura, Jeff Wesner and Mark Belk Department of Biology Brigham Young University

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Mason segura jeff wesner and mark belk department of biology brigham young university

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)


Mason segura jeff wesner and mark belk department of biology brigham young university

  • 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


Mason segura jeff wesner and mark belk department of biology brigham young university

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 analysis2

Higher values --> Higher concentration of heavy isotope --> Higher trophic level

Stable isotope analysis


Stable isotope analysis3

Estimate trophic position relative to algal baseline

Stable isotope analysis


Stable isotope analysis4

Estimate trophic position relative to algal baseline

Increase of 3.4 δ15N = 1 trophic level

Stable isotope analysis


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


Mason segura jeff wesner and mark belk department of biology brigham young university

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

Trophic position of fishes varies across sites

3° consumer

all fish p << 0.05

2° consumer

1° consumer

x

x

x

x

1° producer


Trophic position is reduced in absence of leathersides

Trophic position is reduced in absence of leathersides


Mason segura jeff wesner and mark belk department of biology brigham young university

Habitat is suitable for leathersides


Is this a true reduction in overall food chain length

Is this a true reduction in overall food chain length?


Mason segura jeff wesner and mark belk department of biology brigham young university

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

True reduction in food chain length?

Need info on predators

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer


Mason segura jeff wesner and mark belk department of biology brigham young university

Estimated reduction in food chain length

x


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


Mason segura jeff wesner and mark belk department of biology brigham young university

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


Mason segura jeff wesner and mark belk department of biology brigham young university

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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