1. Predation as a mechanism of invasion resistance
Consumption of non-native Crassostrea ariakensis oysters by the blue crab, Callinectes sapidus
Melanie J. Bishop, Charles H. Peterson
University of North Carolina at Chapel Hill

2. Crassostrea ariakensis
Rapid growth
Early maturity
Broad native range

3. + = ? Crassostrea ariakensis Blue crabs Rapid growth Early maturity
Broad native range
“Keystone” predator

4. Laboratory experiments
In sandy-bottomed aquaria, using triploid oysters
minimizes risk
enables observation of foraging
Single adult crabs (> 80 mm SH)
Satiated and starved
Equal numbers of C. ariakensis and C. virginica (25 of each)
Oysters enumerated every 12 hr
Crabs allowed to feed until ~25% oysters consumed
C. virginica
C. ariakensis

5. Consumption of small (~25 mm) and large (~35 mm) C
Consumption of small (~25 mm) and large (~35 mm) C. ariakensis (A) and C. virginica (V) 2

6. Consumption of large ([L], 40 mm) and small ([S], 30 mm) oysters2

7. Is consumption of C. ariakensis affected by experience?

8. Are blue crabs choosing C. ariakensis?

9. Force required to crush oysters

10. Transplant experiment
2. C. virginica tissue into C. virginica shell
1. C. ariakensis tissue into C. ariakensis shell
4. C. ariakensis tissue into C. virginica shell
3. C. virginica tissue into C. ariakensis shell
If shell strength is sole factor that determines relative rate of consumption of the two species: rate of consumption 1 = 3; 2 = 4

11. Results: Transplant experiment

12. Summary of results
Consumption: A > V across large range of sizes
Mechanism: biomechanics of shell strength
Penalty for rapid growth of C. ariakensis is thin shell
Results conflict with the prevailing dogma that rapid development is a good predictor of invasion potential

13. So what?

14. Applying results of laboratory experiments to the real world
Use predation on C. virginica as standard
Shells of mm C. ariakensis are as resistant to crushing as mm C. virginica
C. ariakensis appears less gregarious than reef-forming C. virginica
Compare environmental tolerances of predator and prey
Blue crabs and C. ariakensis tolerate similar environmental conditions
Consideration of evolutionary history of C. ariakensis

15. Acknowledgements
This research was funded by the North Carolina Division of Marine Fisheries and the Golden Leaf Foundation.
J. Braddy and M. Ulery assisted with the collection of blue crabs and D. Schmitt with the rearing of oysters.
J. Farmer, M. Moretz, C. Peterson, C. Waters, and the 2004 Morehead City Carolina Environment Program class helped with measurements of shell strength.
Dr S. Allen Jr. of the Virginia Institute of Marine Sciences provided triploid C. ariakensis; S. Kemp (North Carolina Sea Grant) provided C. virginica.