Life-History Strategies of Fishes

Rainer Froese

IfM-GEOMAR

Content

• All data from FishBase

• Choice of key traits

• Combinations of traits

• Life history strategies and Phylogeny

• Exploring life-history space

• Testing evolutionary theories

• Success of life-history strategies

Classes of

Fishes

Phylogeny

Classes Orders

Families

Genera Species

Actinopterygii (ray-finned fishes)

45 467 4,573 27,271

Sarcopterygii (lobe-finned fishes)

3 4 4 11

Elasmobranchii (sharks and rays)

11 44 175 961

Holocephali (chimaeras) 1 3 6 37

Cephalaspidomorphi (lampreys)

1 2 9 42

Myxini (hagfishes) 1 1 7 66

Key Trait: Size

0

1000

2000

3000

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Length (log; cm)

Fre

qu

en

cy

small medium large very large

23,603 species

Size Distribution is Multi-ModalCumming and Havlicek (2002)

0

500

1000

1500

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Length (log; cm)

Fre

qu

en

cy

Key Trait: Trophic Level

0

500

1000

1500

2.0 2.5 3.0 3.5 4.0 4.5 5.0

Trophic level

Fre

qu

en

cy

7,161 species

herbi-vore

omnivore low-level predator mid-levelpredator

top-predator

Key Trait: Productivity(modified after Musick 1999)

Parameter High Medium Low Very low

rmax (1/year) > 0.5 0.16 – 0.50 0.05 – 0.15 < 0.05

td (years) <1.4 1.4 - 4.4 4.5 - 14 > 14

Interest rate (%) > 65 17 – 65 5 - 16 < 5

K (1/year) > 0.3 0.16 – 0.30 0.05 – 0.15 < 0.05

Fecundity (1/year) > 10,000 100 – 1000 10 – 100 < 10

tm (years) < 1 2 – 4 5 – 10 > 10

tmax (years) 1 – 3 4 – 10 11 – 30 > 30

Key Traits: Productivity

Productivity Species Percent

Very low 263 10.5

Low 1016 40.5

Medium 879 25.0

High 353 14.0

2,511 species

Productivity is a Proxy for Metabolism

10

100

1000

10000

1 High 2 Medium 3 Low 4 Very low

Productivity

Oxy

ge

n c

on

sum

ptio

n (

mg

/kg

/h)

Trait Correlation: Size vs Troph

1

10

100

1000

10000

1 Herb 2 Omni 3 Low 4 Mid 5 Top

Trophic groups

Le

ng

th (

cm)

Trait Correlation: Size vs Productivity

1

10

100

1000

10000

1 Very low 2 Low 3 Medium 4 High

Productivity groups

Le

ng

th (

cm)

Trait Correlation: Trophic Level vs Productivity

2.0

3.0

4.0

5.0

1 Very low 2 Low 3 Medium 4 High

Productivity groups

Tro

ph

ic le

vel

Phylogeny Limits Traits: Size

HagfishLampreys

ChimaerasSharks & rays

Lobe-finnedRay-finned

1

10

100

1000

10000

1 2 3 4 5 6

Classes

Le

ng

th (

cm)

small

medium

large

very large

Phylogeny Limits Traits: Troph

HagfishLampreys

ChimaerasSharks & rays

Lobe-finnedRay-finned

2.0

3.0

4.0

5.0

1 Myx 2 Cep 3 Hol 4 Ela 5 Sar 6 Act

Classes

Tro

ph

ic le

vel

Phylogeny Limits Traits: Productivity

Class Productivity Species Percent

Myxini Low 66 100

Cephalaspidomorphi Low 16 36

Medium 2 5

Holocephali Low 37 100

Elasmobranchii Very low 206 21

Low 528 55

Sarcopterygii Very low 10 91

Actinopterygii Very low 47 0.2

Low 369 1.4

Medium 877 3.2

High 353 1.3

Available Data are Biased

• Combined available data for 1,880 species are biased towards large, commercial, northern-hemisphere, temperate species

• Solution: Use modelling approach to expand data base

Expanding the Database: Trophic Level

2

2.5

3

3.5

4

4.5

5

1 10 100 1000

Length (cm)

Tro

ph

ic l

evel

Trophic level of 97 species of Genus Epinephelus as a function of their body length.

Top

Medium

Low

Residuals of Modelled Troph

0

500

1000

1500

2000

2500

-2 -1 0 1 2 3

Species (log; n)

Fre

qu

en

cy

Residual Troph

Expanding the Database: Productivity (K)

.01

.1

1

10

1 10 100 1000

Length (cm)

K (

1/y

ea

r)

Von Bertalanffy growth parameter K plotted over maximum length for Family Serranidae

High

Medium

Low

Very low

Modelled vs Observed K

0.0

0.1

1.0

10.0

0.01 0.10 1.00 10.00

K observed (1/year)

K p

red

icte

d (

1/y

ea

r)

Life-History Strategies

• The extended data set contains 20,480 species, nearing a census

• Bias towards large northern species has disappeared

• Of 80 possible combinations of traits only 50 are used

• Three strategies are used by 60% of the species

Occupation of Size-Troph Space

Small Medium LargeVerylarge

Herb

OmniLow

MidTop

0

2000

4000

6000

8000

10000

12000

Occupation of Size-Productivity Space

Small MediumLarge

Verylarge

Very low

Low

MediumHigh

0

2000

4000

6000

8000

10000

Occupation of Troph-Productivity Space

HerbOmni

LowMid

Top

Very low

Low

MediumHigh

0

2000

4000

6000

8000

10000

Testing of Evolutionary Theories

• Predictions of nine evolutionary theories (r-K, succession, temperature, area, etc) were tested

• 88-100% of the predictions were correct

• In case of conflicting predictions temperature theory usually prevailed over r-K and succession theories

Success of Life-History Strategies

• High abundance and wide distribution were taken as indicators of success

• Strategies associated with high abundance or small to medium range had highest species numbers

• Productivity of threatened fishes was significantly lower than that of non-threatened fishes

Thanks to the FishBase Team

Thanks to our Donors

Thank You

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