Biodiversity of Fishes

Size Matters(20.11.2014)

Rainer Froese

2

Extreme Size in Fishes

• What are the largest fishes on Earth?– FishBase, Tools, World Records

• 10 largest fishes

• What are the smallest fishes on Earth?– FishBase, Tools, World Records

• 10 smallest fishes

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Why Does Size Matter?Some Things Increase!

• Predators are larger than their prey• FB, FishBase Book, Trophic Ecology, The Predators Table

• Swimming speed increases with body length• FB, FishBase Book, Morphology and Physiology, The

Swimming and Speed Tables

• Fecundity increases with size (Fec = aLb) median b = 3

• FB, Coryphaena hippurus, More information, Fecundity,

USA - Florida current, a = 0.252, b = 3.12

calculate Fec for 100 and 200 cm

• Publications increase with size

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Why Does Size Matter?Some Things Decrease!

• Metabolism decreases with size• FB, Oreochromis niloticus, More information, Metabolism, Relative

oxygen consumption graph

• Growth decreases with size• FB, O. niloticus, More information, Growth, Auximetric graph

• Natural mortality decreases with size• FB, O. niloticus, More information, Growth, M vs. Linf graph

• Relative brain size decreases with size• FB, O. niloticus, More information, Brains, Relative brain weight

graph

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Sometimes Size Doesn’t Matter

• Size at maturity• FB, Oreochromis niloticus, More information,

Growth, Reproductive load graph

• Body proportions• FB, O. niloticus, More information, L-L relationship,

e.g. SL = a + b TL

if a = 0 then SL is a fixed ratio of TL

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Size Distribution

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

Frequency distribution of maximum lengths in 23,685 species of fishes, Median = 15.9 cm

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Exercises

Discuss with regards to size, phylogeny, habitat and trophic level (FB, Tools, World records):

• Group 1: 10 largest fishes

• Group 2: 10 smallest fishes

• Group 3: 10 fastest fishes (discuss fins)

• Group 4: 10 oldest fishes