The Effect of Fishing on Species and Genetic Diversity

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The Effect of Fishing on Species and Genetic
Diversity
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• Genetic resources are an important element of
  conservation
• Species
• Within Species

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I. The Loss of Species

• Is this a problem in the sea?
• How do we know?

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Latimeria chalumnae (coelacanth) c. 1938
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Documented Extinction

• Stellers 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)

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Sea Turtles, Sharks, Rays ...
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The Role of Fishing in Extinction Events
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II. Loss of Populations
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Pacific Salmonids

• Population rich
• 106 populations extirpated in US
• 142 populations extirpated in Canada
• In the last 30 yrs over 40 of range lost

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63
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4VsW September/October 1996 longline survey
catches
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Marine fish have much more genetic structure
than previously supposed
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Maintenance of Genetic Diversity

• Organization of populations in time and space
• Ratio of within and among population variation

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Events Prior to Extinction

• Extirpation
• Range contraction
• Fragmentation

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• 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

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Brosme brosme (cusk) Abundance 1970-2000
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Loss of Populations Loss of Genetic Diversity
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• 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
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III. Loss of within population genetic diversity
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Selective Fishing
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• 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

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Traits affected by fishing?

• Weight-at-age
• Length-at-age
• Age-at-maturity
• Length-at-maturity
• Spawning season
• Number and size of eggs

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Selective fishing can cause heritable differences
in life-history traits that control sustainable
yield
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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

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Numbers are not enough