the effect of fishing on species and genetic diversity
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The Effect of Fishing on Species and Genetic Diversity
• Genetic resources are an important element of conservation– Species– Within Species
I. The Loss of Species
• Is this a problem in the sea?
• How do we know?
Latimeria chalumnae (coelacanth) c. 1938
Documented Extinction
• Steller’s Sea Cow• Caribbean Monk Seal• Eelgrass Limpet• Rocky Shore Limpet• Asian Periwinkle• Horn Snail
• New Zealand Grayling• Sea Mink• Great Auk• Vanvoorstia
bennettiana (Australian red alga)
Sea Turtles, Sharks, Rays ...
The Role of Fishing in Extinction Events
II. Loss of Populations
Pacific Salmonids
• Population rich– 106 populations extirpated in US– 142 populations extirpated in Canada– In the last 30 yrs over 40% of range lost
4VsW September/October 1996 longline survey catches
46
43
63 57
Marine fish have much more genetic structure than previously supposed
Maintenance of Genetic Diversity
• Organization of populations in time and space
• Ratio of within and among population variation
Events Prior to Extinction
• Extirpation– Range contraction– Fragmentation
• Adriatic Sea stock of Beluga Sturgeon
• Atlantic Ocean population of Gray Whale
• Gulf of St. Lawrence walrus
– populations of 82 species of marine fish in North America believed to be at risk
Brosme brosme (cusk) Abundance 1970-2000
Loss of Populations = Loss of Genetic Diversity
-60 -55 -50 -45 -40
42
44
46
48
50
52
54
56
2J
3K
3M
3N
3O
3L
1964
1978
1990's
Newfoundland
Labrador
NE Newfoundland Shelf
The Grand Bank
Flemish Cap
• A significant amount of genetic diversity could be attributed to spatial structure • No variance component could be attributed to temporal changes
Ruzzante, Taggart et al. In Press. Stability in the historical pattern of genetic structure of Newfoundland cod (Gadus morhua) despite the catastrophic decline in population size from 1964 to 1994. Conservation Genetics
III. Loss of within population genetic diversity
Selective Fishing
25
35
45
55
65
Siz
e a
t ag
e (
cm)
1970 1975 1980 1985 1990 1995
age 3
age 5
age 7
0
50
100
150
0
10
20
30
Nu
mb
er
per
to
w (
all
siz
es)
Adu
lt n
um
be
r p
er
tow
1970 1975 1980 1985 1990 1995 2000
adult all sizes
• By removing the large fish selectively over time the remaining fish are slow-growing and early-maturing
• Genetic or Ecological?– temperature– abundance of prey– degree of competition
Traits affected by fishing?
• Weight-at-age
• Length-at-age
• Age-at-maturity
• Length-at-maturity
• Spawning season
• Number and size of eggs
Selective fishing can cause heritable differences in
life-history traits that control sustainable yield
Problems and Solutions
• Species extinction
• Genetic complexity
• Selective fishing
• Address at the population level
• Manage spawning components
• Reduce fishing intensity• Structure effort• Reduce selectivity• Reduce fishing intensity
Numbers are not enough
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