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Biodiversity of FishesSummary
Rainer Froese(05.02.15)
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Phylogeny of fishes
Classes Common ancestor(million
y)
Orders(n)
Families(n)
Genera(n)
Species(n, %)
Myxini (hagfishes) 600 1 1 6 78 0.2
Cephalaspidomorphi (lampreys)[Petromyzontida]
450 1 3 10 47 0.1
Holocephali (chimaeras)[Chondrichthyes]
420 1 3 6 50 0.1
Elasmobranchii (sharks and rays)[Chondrichthyes]
420 12 51 188 1,158 3.5
Sarcopterygii (lobe-finned fishes)
420 3 4 4 8 0.04
Actinopterygii (ray-finned fishes)
400 46 487 4,833 31,608 95.9
Total 64 549 5,047 32,949 100
FishBase 11/2014http://www.fishbase.org/tools/Classification/ClassificationTree.php
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Fish Diversity of the Oceans
Arctic 130
Atlantic4,900
Pacific10,500Indian
6,000
Pacific10,500
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 Sea190
Mediterranean700
Caribbean1,600
Canary1,300
South Brazil970
Patagonian340
Benguela820
Greenland190
Humboldt750
California800
Alaska320
Hawaiian840
Red Sea1,200
Agulhas1,400
Bay of Bengal700
West470
Indonesian2,400
East1240
Australian
East-China1,040
Polynesian810
Weddell Sea25
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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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Size Matters• Largest fish: Whale shark, 18 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• Metabolic rate, relative brain size, relative gill
area and K, rmax 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
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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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
Typical value for b ~ 3 -> isometric growth
For a = 0.01 (fusiform), 0.1 (roundish), 0.001 (eel-like)
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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 (years)
Wt = Winf (1 – exp(-K * (t – t0)))b
b = 3 or exponent of length-weight relationship
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Growth in Weight
0
2
4
6
8
10
12
14
16
18
0 5 10 15 20 25
Age (years)
Weig
ht
(kg
)
maturity
max growth
max reproductive biomass
asymptotic weight
Gadus morhua , Linf = 120 cm,K = 0.14, M = 0.2, rel Fec = 20%
average adult lifespan
max age
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Whale shark vs Fin whale
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60
Age (years)
Len
gth
(cm
)
Fin whale
Whale shark
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The M Equation
Nt = N0 e –M t
Where
M is the instantaneous rate of natural mortality
N0 is the number of specimens at a t = 0
Nt is the number of specimens at time t
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M = 0.2
0
200
400
600
800
1000
1200
0 5 10 15 20 25
Cohort age (years)
Co
ho
rt n
um
ber
s
Nt = Nts * exp(-M*(t - ts))
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Average Adult Life Expectancy
x
x
y
xl
dl
E
y
ME
1
where Ex is the average life expectancy after reaching age x and l are the probabilities of reaching x and subsequent ages. If mortality M is constant, then the equation simplifies to
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Reproductive Strategies
Froese & Pauly 2013, Fish Stocks, Encyclopedia of Biodiversity, Academic Press
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Length at Maturity for Different Reproductive Strategies
Froese & Pauly 2013, Fish Stocks, Encyclopedia of Biodiversity, Academic Press
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Stock-Recruitment Relationships
(N)
(tonnes)
Spawning stock biomass
Recruits
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Use of Hockey-Stick in Management
Conceptual drawing of the hockey stick relationship between spawning stock size and recruitment. SSBlim marks the border below which recruitment declines, SSBpa marks a precautionary distance to SSBlim, and 2 * SSBpa can be used as a proxy for SSBmsy, the stock size that can produce the maximum sustainable catch [ContHS.xlsx]. (Froese et al. in prep.)
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BioDivPopGrowthMSY.xls
Population Growth
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BioDivPopGrowthMSY.xls
Logistic Curve Properties
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The Schaefer Production Model
BioDivPopGrowthMSY.xls
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Surplus Production Implications
• Surplus production (Y) is the production of biomass beyond what is needed to maintain current population size
• If a fishery only catches the surplus production, then the population size remains
• If a fishery catches more, then the population shrinks
• If it catches less, then the population grows
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Fisheries Management Basics
0
2000
4000
6000
8000
0 20 40 60 80 100
Fishing Effort (hours)
Cat
ch i
n k
g a
nd
Val
ue/
Co
st i
n €
MSY
Cost of fishing
€
€€
MEY
Fpa
?
Flim
†
Economicoverfishing
Growthoverfishing
Recruitmentoverfishing
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EU Fisheries Management
0
2000
4000
6000
8000
0 20 40 60 80 100
Fishing Effort (hours)
Cat
ch i
n k
g a
nd
Val
ue/
Co
st i
n €
MSY
Cost of fishing
€
€€
MEY
?
Flim
†
Subsidies
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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 (>1mm - 10 cm) or numerous and small (< 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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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 Atlas1883
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Questions?