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
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
Loss of Populations = Loss of Genetic Diversity
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 Conservation Genetics
III. Loss of within population genetic diversity
Selective Fishing
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