A preliminary comparison of the trophic structure of some large marine

ecosystems

Rainer Froese, IfMUwe Piatkowski, IfMStefan Garthe, FTZDaniel Pauly, UBC

Overview

• Need to Understand Marine Ecosystems

• Available data: species composition, trophic level of species

• Approach: compare trophic signatures between groups of organisms and between ecosystems

Hypotheses

• Hypothesis I: A given taxonomic group will have similar signatures in similar ecosystems

• Hypothesis II: Different taxonomic groups will have different signatures

Number of Marine Fish Species by Trophic Level

2

2.5

3

3.5

4

4.5

5

1 10 100 1000 10000Number of Fish Species

Tro

ph

ic L

evel

Troph = Mean Troph of food + 1

Trophic Signatures of Fish Species: Tropical LMEs

2

2.5

3

3.5

4

4.5

5

1 10 100 1000 10000

Number of Fish Species

Tro

ph

ic L

evel

South China Sea

Caribbean

trophic level 3.2

Trophic Signatures of Fish Species: Tropical and Temperate, Brackish LMEs

2

2.5

3

3.5

4

4.5

5

1 10 100 1000 10000

Number of Fish Species

Tro

ph

ic L

evel

Baltic

Black Sea

South China Sea

Caribbean

trophic level 3.2

2

2.5

3

3.5

4

4.5

5

1 10 100 1000 10000

Number of Fish Species

Tro

ph

ic L

evel

Baltic

Black Sea

South China Sea

Caribbean

North Sea

trophic level 3.2

Trophic Signatures of Fishes in Five LMEs

Mean Max Length of Fishes by Trophic Level

2

2.5

3

3.5

4

4.5

5

0 25 50 75 100 125 150 175

Mean max. Length of Fish Species (cm TL)

Tro

ph

ic L

evel

Baltic

Black Sea

South China Sea

Caribbean

North Sea

Trophic Structure of Fish, Birds, Cephalopods and Marine Mammals in the North Sea

2

2.5

3

3.5

4

4.5

5

1 10 100 1000

Number of Species

Tro

ph

ic L

ev

el

Fish (186)

MarineMammals (22)

Cephalo-pods (20)

Birds (69)

Trophic Pyramid by Species Numbers for the North Sea

0 500 1000 1500

2-2.5

2.5-3

3-3.5

3.5-4

4-4.5

4.5-5 Fish

Birds

Mammals

Cephs

Benthic invertebrates

Planktonic invertebrates

Conclusions

• Species Composition of Ecosystems and Trophic Signatures are Long-term Characters

• Trophic Signatures Can be Used to Classify Groups of Organisms and LMEs

• Strong Separation between Vertebrates and Invertebrates at Troph 3

• Finer Resolution Needed for Lower Levels

Thank You

We thank the FishBase team for encoding much of the data used in this study and for programming the various tools (TrophLab, Trophic Pyramids).

Data and tools are available at

www.fishbase.org