regime change in a large river fish assemblage mark pyron center of aquatic biology and fisheries...

Regime Change in a Large River Fish Assemblage

Mark PyronCenter of Aquatic Biology and FisheriesEnvironmental Science

Purdue Chapter of IN AFS

Collaborators:

Topics

• Wabash River

• Body size analysis– Change with time

• Food web analysis

Wabash River•2nd largest trib of Ohio River

•85,000 km2 watershed

•764 km long

History of Wabash River• -1900: Abundant and diverse fishes

History of Wabash River

• pre-1900: Abundant and diverse fishes

• 1900 – 1974: point source pollution, agriculture, dam building

History of Wabash River

• pre-1900: Abundant and diverse fishes

• 1900 – 1974: point source pollution, agriculture, dam building

• 1974: Clean Water Act

History of Wabash River

• pre-1900: Abundant and diverse fishes

• 1900 – 1974: point source pollution, agriculture, dam building

• 1974: Clean Water Act

• 1974 – 2015: invasive species, nutrient and sediment reduction

Carroll

Tippecanoe

Warren

Fountain

ParkeV

erm

illio

n

Vigo

Sullivan

Terre Haute

Clinton

10 km

Indiana

N

Fish work:Jim Gammon collected 1968-98

Lauer & Pyron 2001-8

Jim Gammon began project 1968-98

•500-m sites

•Boat electrofishing

Sampling Protocol:

• Electrofish 500 m

• Collect all fishes

• Measure, release

Sampling Protocol:

Gammon’s results:

• High diversity: 100+ species

• Recovering from pollution• IBI scores improved

Longterm assemblage: body size analysis

• Convert size-abundance matrix into size bins• Regress abundances against size bins

Examine organisms by size

• Convert size-abundance matrix into size bins• Regress abundances against size bins• Steeper with exploitation• Steep regression = inefficient ecological transfer

Longterm assemblage:

• Steeper with exploitation 1974-93

1974-931994-2008

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

1970 1975 1980 1985 1990 1995 2000 2005 2010

Size

-Spe

ctra

Slop

eSize spectra slope:

Proxy for ecological (transfer) efficiency

Trophic Groups

Planktivores

fishofohio.com

Gizzard Shad miseagrant.umich.edu

Silver Carp

Benthic invertivores

tnfish.org

ohiodnr.gov

Trophic Groups

Freshwater Drum

Shorthead Redhorse

Blue Sucker

Planktivores

fishofohio.comGizzard Shad

miseagrant.umich.edu

Silver Carp

Benthic invertivores

tnfish.org

ohiodnr.gov

Trophic Groups

Freshwater Drum

Shorthead Redhorse

Blue Sucker

Piscivores

Spotted Bassohiodnr.gov Longnose Gar

tpwd.texas.gov

Planktivores Gizzard Shad

fishofohio.com

Changes in Trophic Groups

Community shift ~ 1992

• Persistent change in structure and function of a system

• Cause?

• Nutrients, invasive species, hydrologic alterations, climate change?

Time lag analysis: 1968-2008

• Use only individuals > 162 mm SL• (susceptible to boat electrofisher)

• Was there a large change in fish assemblages in mid-90s?

-0.6 1.0

-1.0

1.0

1968

1969

19701971

1972

1973 1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

19861987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

2001

2002 2003

2004

2005

2006

2007

2008

Redundancy Analysis

Change in assemblage?

Species that drive RDA

-0.8 1.0

-0.6

0.8

AmercEel

BighCarp

BigmBuff

BlacBuff

BlacBull

BlacCrap

BlacRedh

BlueCatf

BlueSuckBluegill

BowfinBurbot

ChanCatf

ChesLamp

CommCarp

FlatCatf

FresDrum

GizzShad

GoldRedhGoldeye

Goldfish

GrasCarp

GrasPick

GreaRedh

GreeSunfHighCarp

LargBass

LongSunf

LongnGar

MooneyeNortHogs

PaddleFs

QuilCarpRedeSunf

RivrCarp

RivrChub

RivrRedhRockBass

Sauger

ShorRedh

ShortGar

ShovStur

SilvCarp

SilvLamp

SilvRedhSkipHerr SmalBass

SmalBuff

SpotBass

SpottGar

SpotSuck

Walleye

WhitBass

WhitCrapWhitSuck

YellBass

YellBull

AmBrooLm

-0.6 1.0

-1.0

1.0

1968

1969

19701971

1972

1973 1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

19861987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

2001

2002 2003

2004

2005

2006

2007

2008

Food Web Analysis

• Isotopes: 13C and 15N ratiosMuseum archives

Pre-1992 vs Post -1992

–Piscivores–Benthic invertivores–Planktivores

• Mussels• Fishes

Food web analysis:

sofia.usgs.gov

-25.0-25.8-26.6-27.4-28.2-29.0-29.8

18

17

16

15

14

13

12

Mean d15C ratio

Mea

n d1

3N r

atio

Pre 1992Post 1992

Benthic Invertivores

Benthic Invertivores

Planktivore/Omnivore

Planktivore/Omnivore

Silver Carp

Planktivore / Detritivore

MusselsMussels

Silver Carp consume pelagic detritus

miseagrant.umich.edu

Mean d13C

Mea

n d1

5N

-25.0-25.8-26.6-27.4-28.2-29.0-29.8

18

17

16

15

14

13

12

Mean d15C ratio

Mea

n d1

3N r

atio

Pre 1992Post 1992

Benthic Invertivores

Benthic Invertivores

Planktivore/Omnivore

Planktivore/Omnivore

Silver Carp

Planktivore / Detritivore

MusselsMussels

Mussels shifted sourcesM

ean

d15N

-25.0-25.8-26.6-27.4-28.2-29.0-29.8

18

17

16

15

14

13

12

Mean d15C ratio

Mea

n d1

3N r

atio

Pre 1992Post 1992

Benthic Invertivores

Benthic Invertivores

Planktivore/Omnivore

Planktivore/Omnivore

Silver Carp

Planktivore / Detritivore

MusselsMussels

Gizzard shad and Minnows

Mean d13C

-25.0-25.8-26.6-27.4-28.2-29.0-29.8

18

17

16

15

14

13

12

Mean d15C ratio

Mea

n d1

3N r

atio

Pre 1992Post 1992

Benthic Invertivores

Benthic Invertivores

ePlanktivore/Omnivor

Planktivore/Omnivore

Piscivore

Piscivore

Silver Carp

Planktivore / Detritivore

MusselsMussels

Complete assemblage

Mean d13C

Mea

n d1

5N

Algal assemblage changed(gizzard shad stomachs)

2014Water column

Food web changed from 1968-2008

• Shift from pelagic to benthic carbon sources• Causes?

• Changes in nutrients?

• Changes in algal assemblage; both?

1975 1980 1985 1990 1995 2000 2005 20100

0.5

1

1.5

2

2.5

3Daily Statistics for Organic N Concentrations

Year

Org

anic

N C

once

ntra

tion

(mg/

L)

Min

AvgStd

1975 1980 1985 1990 1995 2000 2005 20106

8

10

12

14

16

18

20

Year

Org

anic

N C

once

ntra

tion

(mg/

L)

Max

Food web changed from 1968-2008

• Decrease in N, Increase in P

• Correlated with increased benthic invertivores

Logsdon et al.

Silver Carp fecal pellets transfer nutrients to benthic fishes

• Blue catfish increased growth

• Channel catfish survive

Silver Carp fecal pellets transfer nutrients to benthic fishes

• Blue catfish increased growth

• Shift nutrient source from pelagic to benthic habitat

Plankton consumed by Silver Carp: fecal pellets available to other consumers

AlgaeAlgaeRiparian C3Riparian C3-25.0-25.8-26.6-27.4-28.2-29.0-29.8

18

17

16

15

14

13

12

Mean d15C ratio

Mea

n d1

3N r

atio

Pre 1992Post 1992

Benthic Invertivores

Benthic Invertivores

ePlanktivore/Omnivor

Planktivore/Omnivore

Piscivore

Piscivore

Silver Carp

Planktivore / Detritivore

MusselsMussels

SummarySummary

• Switch in trophic group dominanceSwitch in trophic group dominance• Planktivores to benthivoresPlanktivores to benthivores• Silver Carp and Ag nutrientsSilver Carp and Ag nutrients

• Food web changes: Food web changes: • Shift from pelagic to detritus Shift from pelagic to detritus