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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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 fishes in the Bear River Drainage,

Northern leatherside chub

Upper Bear River (UT, WY), Snake River

Threatened species

Described in 2004

Need ecological information for management and recovery


Background1

Background fishes in the Bear River Drainage,

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 fishes in the Bear River Drainage,

Leath. absent

Leath. present

2010/11 - Factors affecting abundance

2010/11 - Factors affecting occurrence

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


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


N fishes in the Bear River Drainage,

Bear River


Stable isotope analysis

Stable isotope analysis fishes in the Bear River Drainage,

  • 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 fishes in the Bear River Drainage,

  • 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 fishes in the Bear River Drainage, --> Higher concentration of heavy isotope --> Higher trophic level

Stable isotope analysis


Stable isotope analysis3

Estimate trophic position relative to algal baseline fishes in the Bear River Drainage,

Stable isotope analysis


Stable isotope analysis4

Estimate trophic position relative to algal baseline fishes in the Bear River Drainage,

Increase of 3.4 δ15N = 1 trophic level

Stable isotope analysis


Stable isotope analysis5

Estimate trophic position relative to algal baseline fishes in the Bear River Drainage,

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 fishes in the Bear River Drainage,

all fish p << 0.05

2° consumer

Trophic position of fishes varies across sites

1° consumer

1° producer


Trophic position of fishes varies across sites fishes in the Bear River Drainage,

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Trophic position of fishes varies across sites fishes in the Bear River Drainage,

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Trophic position of fishes varies across sites fishes in the Bear River Drainage,

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Trophic position of fishes varies across sites fishes in the Bear River Drainage,

3° consumer

all fish p << 0.05

2° consumer

1° consumer

1° producer


Trophic position of fishes varies across sites fishes in the Bear River Drainage,

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 fishes in the Bear River Drainage,


Habitat is suitable for leathersides fishes in the Bear River Drainage,


Is this a true reduction in overall food chain length

Is this a true reduction in overall food chain length? fishes in the Bear River Drainage,


True reduction in food chain length? fishes in the Bear River Drainage,

Need info on predators

3° consumer

2° consumer

1° consumer

1° producer


True reduction in food chain length? fishes in the Bear River Drainage,

Need info on predators

3° consumer

2° consumer

1° consumer

1° producer


True reduction in food chain length? fishes in the Bear River Drainage,

Need info on predators

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer


True reduction in food chain length? fishes in the Bear River Drainage,

Need info on predators

3° consumer

2° consumer

1° consumer

x

x

x

x

1° producer


Estimated reduction in food chain length fishes in the Bear River Drainage,

x


Theory explaining food chain length

Ecosystem productivity fishes in the Bear River Drainage,

Ecosystem size

Theory explaining food chain length

Food Chain Length

Disturbance

McHugh et al. EcolLett 2010


Theory explaining food chain length1

Ecosystem productivity fishes in the Bear River Drainage,

Ecosystem size

Theory explaining food chain length

Food Chain Length

Disturbance

McHugh et al. EcolLett 2010


Theory explaining food chain length2

Ecosystem productivity fishes in the Bear River Drainage,

Ecosystem size

Theory explaining food chain length

Food Chain Length

Disturbance

McHugh et al. EcolLett 2010


Food webs

fish fishes in the Bear River Drainage,

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


Intermediate predators occur at leatherside sites fishes in the Bear River Drainage,

(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


Acknowledgements northern leatherside chub.

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? northern leatherside chub.

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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