Julien CUCHEROUSSET

CNRS – University Paul Sabatier Toulouse, France

Email: julien.cucherousset@univ-tlse3.fr

An introduction to the ecological impacts of invasive freshwater fishes

Gozlan 2008 Fish Fish

Impacts of non-native fish: Rationale

Fish are the most frequently introduced organisms in freshwater ecosystems

Reasons - Aquaculture - Angling/Sport - Fisheries - Ornamental

Fish are the most frequently introduced organisms in freshwater ecosystems

Reasons - Aquaculture - Angling/Sport - Fisheries - Ornamental Gozlan 2008 Fish Fish

Native species

Ln (Maximum Body Size) 0 1 2 3 4 5 6 7

Den

sity

0.0

0.1

0.2

0.3

0.4

Blanchet et al. 2010 Ecol Let

Impacts of non-native fish: Rationale

Global distribution of freshwater fish body size:

Fish are the most frequently introduced organisms in freshwater ecosystems

Reasons - Aquaculture - Angling/Sport - Fisheries - Ornamental Gozlan 2008 Fish Fish

=> Introduction of large-bodied species

Native species

Non-native species

Ln (Maximum Body Size) 0 1 2 3 4 5 6 7

Den

sity

0.0

0.1

0.2

0.3

0.4

P < 0.001

Blanchet et al. 2010 Ecol Let

Impacts of non-native fish: Rationale

Global distribution of freshwater fish body size:

Nile perch (Lates niloticus)

European catfish (Silurus glanis)

Largemouth bass (Micropterus salmoides)

Rainbow trout (Oncorhynchus mykiss)

Peacock bass (Cichla ocellaris)

Impacts of non-native fish: Introduced predators

Distribution of body-mass in communities influences their structure and functioning Riede et al. 2011

Eltonian pyramid

Abundance Biomass

Body

mas

s or

trop

hic

leve

l

Trebilco et al. 2013

Body

size

Elton 1927 Lindeman 1942

Ecological pyramid

Impacts of non-native fish: Rationale

Introduced species could modify (directly and indirectly) these patterns

Impacts of non-native fish: Rationale

Terborgh 2015

Distribution of body-mass in communities influences their structure and functioning Riede et al. 2011

Eltonian pyramid

Abundance Biomass

Body

mas

s or

trop

hic

leve

l

Trebilco et al. 2013

Body

size

Elton 1927 Lindeman 1942

Ecological pyramid

New predators New predators

Genetic

Individual

Population

Community

Ecosystem

Cucherousset & Olden 2011 Fisheries

Impacts of non-native fish: Ecological impacts

Genetic

Individual

Population

Community

Ecosystem

Cucherousset & Olden 2011 Fisheries

- Gene transcription - Hybridization

- Behavior - Morphology - Vital rates

- Transmission of pathogens - Invasive fish as parasites - Demographic effects - Distributional effects

- Species extinction - Composition changes - Alteration of food webs

- Biochemical cycles - Energy fluxes between ecosystems - Ecological engineering

Impacts of non-native fish: Ecological impacts

Genetic

Individual

Population

Community

Ecosystem

Cucherousset & Olden 2011 Fisheries

- Gene transcription - Hybridization

- Behavior - Morphology - Vital rates

- Transmission of pathogens - Invasive fish as parasites - Demographic effects - Distributional effects

- Species extinction - Composition changes - Alteration of food webs

- Biochemical cycles - Energy fluxes between ecosystems - Ecological engineering

Impacts of non-native fish: Ecological impacts

Impacts on food-web structure

Zaret & Paine 1973 Science

BEFORE INVASION

Impacts of non-native fish: Food web structure

Zaret & Paine 1973 Science

Introduced predators

BEFORE INVASION AFTER INVASION

=> Strong changes in community and food-web structure

Impacts of non-native fish: Food web structure

Vander Zanden et al. 1999 Nature

Micropterus dolomieu INVASION Ambloplites rupestris

Introduced predators

Trop

hic p

ositi

on

4

3

2

-30 -28 -26 -24 δ13C

40%

60%

Zooplankton

Prey fish

LITTORAL PELAGIC Native predator

LAKES WITHOUT INVASION

Impacts of non-native fish: Food web structure

Salvelinus namaycush

LAKES WITH INVASION

-30 -28 -26 -24 δ13C

20%

80%

Vander Zanden et al. 1999 Nature

Micropterus dolomieu INVASION Ambloplites rupestris

LITTORAL PELAGIC

Zooplankton

Prey fish

Introduced predator

Introduced predators

Native predator

Trop

hic p

ositi

on

4

3

2

-30 -28 -26 -24 δ13C

40%

60%

Zooplankton

Prey fish

LITTORAL PELAGIC Native predator

LAKES WITHOUT INVASION

Impacts of non-native fish: Food web structure

Salvelinus namaycush

Cucherousset et al. 2012 Frontiers in Ecology and the Environment

- Fish community composition

- Species status (native vs non-native)

- Trophic position TP (Fishbase)

13 rivers worldwide

Impacts of non-native fish: Food web structure

Historical

No change in mean trophic position Increased trophic variability

Curr

ent

Mean TP

Historical

CV TP

Curr

ent

p = 0.19 p < 0.01

Impacts of non-native fish: Food web structure

Cucherousset et al. 2012 Frontiers in Ecology and the Environment

Historical

No change in mean trophic position Increased trophic variability

Modified basal structure of food webs

Increased food chain length

Curr

ent

Mean TP

Historical

CV TP

Historical Cu

rren

t

p = 0.19 p < 0.01

Maximum TP

Curr

ent

Curr

ent

Historical

Impacts of non-native fish: Food web structure

Cucherousset et al. 2012 Frontiers in Ecology and the Environment

Minimum TP

Historical

No change in mean trophic position Increased trophic variability

Modified basal structure of food webs

Increased food chain length

=> Trophic dispersion of food webs

Curr

ent

Mean TP

Historical

CV TP

Historical Cu

rren

t

p = 0.19 p < 0.01

Maximum TP

Curr

ent

Curr

ent

Historical

Impacts of non-native fish: Food web structure

Cucherousset et al. 2012 Frontiers in Ecology and the Environment

Minimum TP

Impacts on energy fluxes and ecosystem functioning

0

Knight et al. 2005. Nature

Impacts of non-native fish: Fluxes and ecosystems

0

Knight et al. 2005. Nature

Impacts of non-native fish: Fluxes and ecosystems

Cucherousset et al. 2012 Plos ONE Source: Le silure, géant des rivières (ARTE)

Impacts of non-native fish: Fluxes and ecosystems

45 beaching behaviour observed ⇒ 28% of success rate ⇒ Trophic specialisation

Baxter et al. (2004) Ecology

Impacts of non-native fish: Fluxes and ecosystems

Baxter et al. (2004) Ecology

Impacts of non-native fish: Fluxes and ecosystems

(1) Control

Baxter et al. (2004) Ecology

(2) Habitat alteration

(1) Control

Impacts of non-native fish: Fluxes and ecosystems

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

Impacts of non-native fish: Fluxes and ecosystems

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

(4) Habitat + Invasion

Impacts of non-native fish: Fluxes and ecosystems

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

(4) Habitat + Invasion

Impacts of non-native fish: Fluxes and ecosystems

Terrestrial invertebrates consumed by the native species

1 2 3 4

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

(4) Habitat + Invasion

Impacts of non-native fish: Fluxes and ecosystems

Herbivorous invertebrates biomass

1 2 3 4

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

(4) Habitat + Invasion

Impacts of non-native fish: Fluxes and ecosystems

Primary production

1 2 3 4

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

(4) Habitat + Invasion

Impacts of non-native fish: Fluxes and ecosystems

Emergent invertebrates biomass

1 2 3 4

Baxter et al. (2004) Ecology

(2) Habitat alteration

(3) Trout invasion

(1) Control

(4) Habitat + Invasion

Impacts of non-native fish: Fluxes and ecosystems

Riparian spider density

1 2 3 4

Impacts of non-native fish: Conclusion

Salmonids are an important group of invasive fish and can help filling some of the knowledge gaps in the field of biological invasions:

Julien CUCHEROUSSET

CNRS – University Paul Sabatier Toulouse, France

Email: julien.cucherousset@univ-tlse3.fr

An introduction to the ecological impacts of invasive

freshwater fishes