Biodiversity of Fishes Sharks

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Biodiversity of Fishes Sharks Rays

• Rainer Froese
• IFM-GEOMAR
• Kiel
• 27.11.08

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There are Six Classes of Fishes
Source FishBase 09/2006
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Most Fishes are Small
Frequency distribution of maximum lengths in
23,685 species of fishes. Median 15.9 cm.
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Most Sharks are Large
very large
large
medium
small
Myxini with median 49 cm Cephalaspidomorphi with
median 22 cm Holocephali with median 99 cm
Elasmobranchii with median 78 cm
Sarcopterygii with median 125 cm and
Actinopterygii with median 16 cm.
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Most Fishes are Low-level Predators
herb
low-level predator
omnivore
mid
top predator
Frequency distribution of trophic levels for
7,500 species of fishes median 3.4
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Most Sharks are Mid-level Predators
Trophic level by Class for 7,500 species with
available data Myxini with median 4.2
Cephalaspidomorphi with median 4.2 Holocephali
with median 3.5 Elasmobranchii with median
4.0 Sarcopterygii with median 3.4 and
Actinopterygii with median 3.4.
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How to Estimate Productivity
Modified after Musick (1999)
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Most Fishes have High Productivity
Observed (n 2,621) and modeled (n 24,649)
productivities of fishes. Source FishBase
11/2004 Froese 2005
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Occupation of Size-Troph Space
Source FishBase 11/2004 Froese 2005
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Occupation of Size-Productivity Space
Source FishBase 11/2004 Froese 2005
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Occupation of TrophProductivity Space
Source FishBase 11/2004 Froese 2005
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Occupation of sizeproductivitytroph-space for
20,480 species of fishes. Full cell width is
1000 species.
Source FishBase 11/2004
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Occupation of sizeproductivitytroph-space for
620 species of sharks and rays. Full cell width
is 1000 species.
Source FishBase 11/2004
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Occupation of sizeproductivitytroph-space for
620 species of sharks and rays. Full cell width
is 145 species.
Source FishBase 11/2004
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Competition among Low-level Predators
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Competition betweenMid-level Predators
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Competition among Top-Predators
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Salinity Tolerance
12,889 14,091
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Climate Zones
3,194 4,023 16,840
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Global Species Richness of Actinopterygii
Source www.aquamaps.org Nov. 2008
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Global Species Richnessof Elasmobranchii
Source www.aquamaps.org Nov. 2008
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Relative Brain Size
519
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Reproductive Guild
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Summary

• Elasmobranchs are the second largest Class of
  recent fishes
• They use only 16 life-history strategies compared
  with 49 used by ray-finned fishes
• They are mostly large, marine, demersal,
  migratory, large-brained, long-living mid-level
  predators of low productivity
• Their niches are dominated by ray-finned fishes
  with typically higher productivity
• They survived because of superb hunting
  capabilities (electro-sensing, large brains) and
  low mortality
• Their large size and low productivity makes them
  highly vulnerable to exploitation

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Exercises

• Explore one of these three species in FishBase
• Negaprion brevirostris Lemon shark
• Rhincodon typus Whale shark
• Heterodontus portusjacksoni Port Jackson shark
• Discuss size, tropic level, productivity,
  reproduction and distribution