1. The Effect of Fishing on Species and Genetic Diversity
1) Species diversity: variation in the number and frequency of species in a biological assemblage or community (species composition and relative dominance etc.)
2) Genetic diversity: variation in the amount of genetic information within and among individuals of a population, a species, an assemblage, or a community

2. Genetic resources are an important element of conservation
Species
Within Species
A species is any group within which genetic material can be exchanged between individuals across generations
A unique evolutionary lineage that cannot be replaced once lost
Variability essential to cope with environmental change is found almost exclusively within the genetic structure of the species
Genes are only created through mutation events which operate on scales of ten’s of thousands of years
Genes can be lost in a single generation

3. I. The Loss of Species Is this a problem in the sea? How do we know?
Extinction has always been a part of the earth’s history
average longevity of a species is on the order of 1 to 10 million years, at least for marine invertebrates
Currently there is an accelerated loss of species due to human activities
extinction rates 100 to 1000 times higher than pre-human levels
a potential for these rates to increase by a factor of 10 in the near future

4. Latimeria chalumnae (coelacanth) c. 1938
The discovery of the coelacanth “living fossil”
Previously the lineage was thought to have been extinct for 80 MY
Two species and possibly three with a total abundance of approximately 100,000
Latimeria chalumnae (coelacanth) c. 1938

5. 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)
The total number of marine species is approximately 300,000
In contrast there are only a few documented marine species extinction events
There are many more documented cases of extinction in freshwater and on land

6. Sea Turtles, Sharks, Rays ...
Pipefishes and Seahorses
Sea Turtles, Sharks, Rays ...

7. The Role of Fishing in Extinction Events

8. These fish are very large (the beluga sturgeon is the largest freshwater fish), have very low productivity and specialized habitat requirements

9. II. Loss of Populations
The genetic structure of a species is partitioned within and among populations
Natural selection will act within populations, while the total genetic potential of a species to adapt to environmental change depends on the total genetic diversity among populations
Therefore we must preserve both aspects
Populations may or may not coincide with management units!

10. Pacific Salmonids Population rich 106 populations extirpated in US
142 populations extirpated in Canada
In the last 30 yrs over 40% of range lost
There is a range in the degree to which fish are subdivided into populations
At one extreme are the salmonids which are population rich
Long distance dispersal by passive larval drift has long been cited as resulting in open marine populations
As we accumulate more genetic information we are finding that many species do exhibit spatially explicit population structure, at least at spawning time

11. For years the European eel was thought to be the best example of a species with one large breeding population

12. Cod also has more population structure than previously supposed, despite it being a good disperser!

13. 4VsW September/October 1996 longline survey catches46
This area is a few hundred kms long
The cod resource on the Eastern Scotian Shelf (one management unit) is a complex of spawning components including at least two major offshore groups and a chain of coastal spawning groups
Several of the spawning components also have spring and fall spawning fish 43 63 57
4VsW September/October 1996 longline survey catches

14. Marine fish have much more genetic structure than previously supposed

15. Maintenance of Genetic Diversity
Organization of populations in time and space
Ratio of within and among population variation

16. Events Prior to Extinction
Extirpation
Range contraction
Fragmentation
Long before a species becomes extinct there may be changes to it’s population structure. Loss of populations when at the periphery of a species’ range can result in range contraction. Loss of populations in the midst of a species range can result in fragmentation. Both events have genetic consequences.

17. 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
Extirpation (extinction of a population)

18. Brosme brosme (cusk) Abundance 1970-2000
Range contraction and fragmentation in cusk, a species which is believed to be a resident with a small range
Note that in this particular species declines were seen even in an area on Western Bank that has been closed to fishing since the 1980s

19. Loss of Populations = Loss of Genetic Diversity

20. Erosion of spawning components and severe range contraction in northern cod stock complex of NAFO Divisions 2J3KL
A: Location of spawning stocks during the period
B: Location of spawning cod

21. No variance component could be attributed to temporal changes
A significant amount of genetic diversity could be attributed to spatial structure
No variance component could be attributed to temporal changes
Survival of the spatial pattern of genetic differentiation during the population collapse suggests that if recovery eventually occurs it will likely be through population re-growth rather than by migration
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

22. III. Loss of within population genetic diversity
Overfishing of populations can cause a number of genetic effects when population size becomes too small and we certainly need to maintain viable numbers of animals within each population
However, maintaining large population sizes may not be sufficient
Loss of within population genetic diversity can be insidious in that genes can be lost even when the numbers are high

24. Selective Fishing

25. Changes in the mean length-at-age of haddock on the Eastern Scotian Shelf and the mean number of fish per tow from the summer research vessel survey

26. Changes in the median age and length at 50% maturity of northern cod (NAFO 3Ps)

27. 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

28. Traits affected by fishing?
Weight-at-age
Length-at-age
Age-at-maturity
Length-at-maturity
Spawning season
Number and size of eggs
phenotype = genotype + environment + (genotype x environment)
Many traits are believed to be affected by fishing activities
These include the above, many of which are correlated

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

30. Problems and Solutions
Species extinction
Genetic complexity
Selective fishing
Address at the population level
Manage spawning components
Reduce fishing intensity
Structure effort
Reduce selectivity
Need for more research to increase our understanding of intraspecific variation

31. Numbers are not enough
There is a perception that the remarkable recoveries of some stocks, including many whale species, means that we can reverse the damage we have caused
These “recoveries” by definition must arise from a narrow genetic base
These species may look good numerically but may have problems coping with environmental change or disease
The Caspian seal population fell to very low numbers in the late 1950s and recovered to a population of about 400,000
Last year over 20,000 have died from canine distemper and other viruses