Biodiversity of Fishes Summary

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Biodiversity of FishesSummary

• Rainer Froese
• (05.02.09)

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Phylogeny of fishes
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Size Matters

• Largest fish Whale shark, 20 m, 34 t
• Smallest fish attached male anglerfish, several
  tiny cyprinids gobies, 1 cm, 0.01g
• Max growth rate, fecundity, speed, trophic level,
  life span increase with size
• Relative metabolism, growth, brain size, gill
  area and M decrease with size
• topt 1.65/M, max growth 0.296 Winf, max age
  tmax at 0.95 Linf 4.5/M are constant

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Size Distribution
Frequency distribution of maximum lengths in
23,685 species of fishes, Median 15.9 cm
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Relationship Between Weight and Length

• W a Lb
• with weight in grams and length in cm
• For parameter estimation use linear regression of
  data transformed to base 10 logarithms
• log W log a b log L
• Plot data to detect and exclude outliers, and to
  check for growth stanzas

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Fultons Condition Factor

• K 100 W / L3
• Used to compare fatness or condition of
  specimens of similar size, e.g. to detect
  differences between sexes, seasons or localities.
• Example Condition of a specimen of 10 cm length
  and 10 grams weight
• 1 100 10 / 1000

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Von Bertalanffy Growth Function

• Lt Linf (1 exp(-K (t t0)))
• Where
• Lt length (cm) at age t (years)
• Linf asymptotic length if t infinite
• K parameter indicating how fast Linf is
  approached (1/year)
• t0 hypothetical age at L 0
• Wt Winf (1 exp(-K (t t0)))b

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Growth in Weight
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Whale shark vs Fin whale
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The M Equation

• N N0 e M t
• Where
• M is the instantaneous rate of natural mortality
• N0 is the number of specimens at a previous time
• N is the number of specimens at time t

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M 0.2
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Average Adult Life Span
where Ex is the average life expectancy after
reaching age x and l are the probabilities of
reaching x and subsequent ages. If mortality is
constant then
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Variability in Maturity
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The Mechanics of Sex under Water

• Eggs have to be fertilized (or activated) by the
  right sperms
• Eggs are few and large (gt1mm - 10 cm) or numerous
  and small (lt 1 mm), internal, attached or
  drifting
• Sperms are very small, very numerous, mobile,
  outside
• Survival of gametes in water is short (few
  minutes)
• Courtship and mating aims to increase
  fertilization rate

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Six Zoogeographic Realms
Alfred Russell Wallace, 1876. The Geographical
Distribution of Animals
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Permian, 225 m
Triassic, 200 m
Jurassic, 135 m
Cretaceous, 65 m
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Fish Diversity of the Oceans
Arctic 130
Atlantic 4,900
Pacific 10,500
Pacific 10,500
Indian 6,000
Antarctic 370
Total 16,000 marine or diadromous fishes,
several thousand in more than one Ocean
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Diversity in Large Marine Ecosystems
North Sea 190
Greenland 190
Alaska 320
Mediterranean 700
East-China 1,040
Caribbean 1,600
Canary 1,300
California 800
Red Sea 1,200
Hawaiian 840
Bay of Bengal 700
Indonesian 2,400
South Brazil 970
Agulhas 1,400
Humboldt 750
Polynesian 810
Benguela 820
West 470
East 1240
Australian
Patagonian 340
Weddell Sea 25
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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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Three trawling revolutions
1376 the beam trawl is invented
1880s trawlers gain steam power
Late 20th century the deep sea comes within
reach of the trawl
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The Piscatorial Atlas 1883
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Economics of Fishing
How subsidies induce overfishing
Lets assume a Gordon-Schaefer bioeconomic model
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Thus, global fisheries landings, despite (or
because of) increasing effort, have been
declining since the late 1980s, a fact long
hidden by over-reporting from China
Watson and Pauly (Nature), 2001.
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Fishing Down the Food Web
Pauly et al. (Science, 1998)
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Questions?
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