1. Jennifer Ruesink University of Washington
West Side Story the context, causes, and consequences of the Pacific oyster introduction to Washington State
Jennifer Ruesink
University of Washington

2. Outline Context Causes Consequences
Ruesink, Lenihan, Trimble, Heiman, Micheli, Byers, Kay Introduction of non-native oysters: ecosystem effects and restoration implications. Annu Rev Ecol Evol Syst 36:
Causes
White, Ruesink, Trimble. History and management of native oysters (Ostrea conchaphila) in Washington State. In preparation for special issue of J Shellfish Res
Consequences
Ruesink, Feist, Harvey, Hong, Trimble, Wisehart Changes in productivity associated with four introduced species: Ecosystem transformation of a “pristine” estuary. Mar Ecol Prog Ser 311:
Trimble, Ruesink, Dumbauld. Factors preventing recovery of a historically overexploited shellfish species. In preparation.

3. Context Oyster introductions have occurred frequently
High establishment rate
Vector for numerous other species
Nearly complete replacement of native oyster production

4. Compilation of oyster introductions
Introduction = movement of species from one country/ region to another where it was not previously present
Sources = UN FAO, several earlier reviews (Eldredge 1994, NRC 2004), published papers, personal communications
Number of introductions = _____
Number of recipient locations = ____
Number of species = ____

5. Compilation of oyster introductions
Introduction = movement of species from one country/ region to another where it was not previously present
Sources = UN FAO, several earlier reviews (Eldredge 1994, NRC 2004), published papers, personal communications
Number of introductions = _164_
Number of recipient locations = _73_
Number of species = _16_

6. When did oyster introductions occur?
Charles Elton fingered oyster introductions as the “greatest agency of all that spreads marine animals to new corners of the world”

7. Where have oysters been introduced?19 61 3 41 9 18 4 6 6

8. Which oyster species have been introduced?
C. virginica = 16
C. cortezensis = 1
C. rhizophorae = 3
C. echinata = 5
C. gigas =
C. sikamea = 3
C. ariakensis = 3
S. commercialis = 6
C. iredalei = 2
S. cucullata = 3
C. belcheri = 1
O. edulis = 11
T. chilensis = 3
C. densalamellosa = 1
O. conchaphila = 1
O. puelchana = 1
O’Foighil & Taylor 2000 Molecular Phylogenetics & Evolution 15:301

9. How well did they do?

10. Why were new oysters introduced?
Replace native species
Begin new product (Pacific islands)
Research (12)
Range expansion (4)
By-product (3)

11. Introduced oysters have replaced native oyster production

12. Introduced oysters have vectored many other species

13. Context
Oyster introductions have occurred frequently
High establishment rate
Vector for numerous other species
Nearly complete replacement of native oyster production
However, ecological impacts of introduced oysters are poorly studied:
To what extent do introduced oysters replace “ecosystem function”?
Is recovery of native oysters improved or impaired?

14. Causes
Why were Pacific oysters (Crassostrea gigas) introduced to Washington State?
Harvesting native oysters was no longer economical… but therein lies a story

15. VANCOUVER
SEATTLE
Puget Sound
Willapa Bay
PORTLAND

16. Native oyster Ostreola conchaphila (Carpenter, 1857)
Historic Range: Sitka, AK to Mexico
Maximum 6 cm
Protandrous Hermaphrodite
Brooding Females: ~250,000 larvae/adult
Spawning above 12C for 3+ months/yr.
Subtidal accumulations of shell
Baker 1995

17. The way it used to be? Willapa Bay at low water, late 1800s

18. Willapa Bay – current population between 0 and -2’ MLLW is sparse in eelgrass

19. North Bay, Puget Sound – ~25 million oysters between 0 and -4’, newly recovered

20. Trimble, unpubl.

22. Willapa Bay timeline

23. First harvest restrictions

24. Native oysters described scientifically

25. Tideflat privatization

27. Marine Reserves

29. Almost perfect overlap with original native oyster beds
Oyster Reserves:
Legislated ~1900
Almost perfect overlap with original native oyster beds
Collins, 1888

30. C. virginica introduction
Subsequent introductions:
C. gigas - established
O. edulis
C. sikamea
C. ariakensis

31. Commercial interest shifted to Crassostrea gigas: Imports of spat to the west coast
White, Ruesink, Trimble, unpubl.

32. Secondary production in Willapa Bay shifted from native to non-native shellfish (filtration too)
Ruesink, Feist, Harvey, Hong, Trimble, Wisehart Mar Ecol Prog Ser

33. Research efforts also shifted
Number of holdings in the University of Washington library referring to each species
Scientific literature includes <15 modern papers on O. conchaphila – but this will soon change!

34. Has C. gigas functionally replaced O. conchaphila?
New oyster
Broadcasting
Rapid growth
Intertidal
Reef-building
Native oyster
Brooding
Slow growth
Subtidal
Loose shell

35. Consequences
What are the ecological impacts of Pacific oysters (Crassostrea gigas)?
Interactions with native oysters – directly and indirectly
Effects of shellfish and aquaculture practices on sediment properties, eelgrass, epibiota, fish and crabs are the focus of targeted research funded in part by the shellfish industry

36. Potential Factors Limiting Population Recovery
Reproductive Failure (no)
Settlement Habitat Change (yes)
Pollution and Sedimentation (yes)
Competition (space- yes)
Predation (yes)
Disease (limited)

37. Native oyster recruitment remains high
Long Island Reserve
Spatfall on
Cinder Block Anchors
(-10m)
Middle Sands Reserve

38. Quantitative recruitment time series
Weekly records of spatfall from ,
Native oyster usually > Pacific oyster

39. 1947-2006 Spatfall: O. conchaphila and C. gigas

40. But where do those larvae now settle?
What native oyster beds used to be… maybe… perhaps?

41. Settlement Habitat Change
C. gigas intertidal reefs

42. Settlement Habitat Change
Increased sedimentation from logging in watershed

43. Quantitative assessment of recruitment across habitats

44. Recruitment rate across habitats
Most available habitat

45. 2-factor experiment: 3 elevations, +/- competitors
Tiles on mooring
Day 0 (1 month old)
Day 63
Day 304

46. “HIGH”
(+ 30cm)
MLLW
“LOW”
(- 30cm)

47. “MOORING”
(-1 m)

48. Survival declines when not submerged
F8,112 = 2.8, P = 0.007

49. Impacts of competitors
Ectopleura crocea
Botryllus spp.
>45 introduced species reported in Willapa Bay
Wonham & Carlton 2005 Biol Inv

50. Competitors Reduce Survival
F1,112 = 42.4, P < 0.001

51. Competitors Reduce Growth
F4,61 = 5.5, P = 0.001

52. Interactions between Washington’s native and non-native oysters
Recruitment “sink”:
Intertidal aquaculture
Naturalized intertidal reefs
Recruitment, but poor intertidal survival
Overgrowth?
High sustained recruitment indicates presence of core reproductive population
Historical vector of non-native predators and competitors -

53. May 2004 Bare Gravel Pacific shell Crushed Pacific shell Native shell
Live natives

54. Recruitment improved at lower elevations and on natives

56. Unstable treatments washed away at most sites

57. Stable treatments were heavily fouled at most sites

58. Rosettes – natives grew and survived

59. Rosettes – buried at other sites

60. Shell on ground – not a functional replacement for natives