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West Side Story
the context, causes, and consequences of the
Pacific oyster introduction to Washington State
Jennifer Ruesink
University of Washington
Outline
• Context
– Ruesink, Lenihan, Trimble, Heiman, Micheli, Byers, Kay. 2005.
Introduction of non-native oysters: ecosystem effects and restoration
implications. Annu Rev Ecol Evol Syst 36:643-689
• 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. 2006. Changes in
productivity associated with four introduced species: Ecosystem
transformation of a “pristine” estuary. Mar Ecol Prog Ser 311:203-215
– Trimble, Ruesink, Dumbauld. Factors preventing recovery of a
historically overexploited shellfish species. In preparation.
Context
• Oyster introductions have occurred
frequently
• High establishment rate
• Vector for numerous other species
• Nearly complete replacement of native
oyster production
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 = ____
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_
Cumulative number of transfers
When did oyster introductions occur?
120
100
80
Charles Elton fingered oyster
introductions as the “greatest agency
of all that spreads marine animals to
new corners of the world”
60
40
20
0
1850
1870
1890
1910
1930
1950
1970
1990
2010
Where have oysters been introduced?
19
61
3
9
41
18
4
6
6
Which oyster species have been introduced?
C. virginica = 16
C. rhizophorae = 3
C. gigas = 64 + 6
C. ariakensis = 3
S. commercialis = 6
S. cucullata = 3
C. cortezensis = 1
C. echinata = 5
C. sikamea = 3
C. iredalei = 2
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
C.
gi
ga
s
C.
vir
gi
ni
ca
O
.e
du
lis
C.
an
S.
gu
co
la
ta
m
m
er
cia
lis
C.
ec
hi
na
C.
ta
ar
ia
ke
C.
ns
is
rh
iz
op
ho
ra
C.
e
sik
am
ea
S.
cu
cu
lla
ta
T.
ch
ile
ns
is
Frequency of locations
How well did they do?
70
60
50
Unknown
40
30
20
10
0
Failed
Established
Why were new oysters introduced?
•
•
•
•
•
Replace native species
Begin new product (Pacific islands)
Research (12)
Range expansion (4)
By-product (3)
10-year production 1993-2002
(metric tons shucked)
Introduced oysters have replaced native
oyster production
Introduced
Native
Uncertain
3e+7
2e+6
1e+6
0
ic
Afr
a
W
A
US
SA
U
E
a
da
/NZ
ric
a
e
na
i
l
a
m
C
tra
SA
us
e
rop
u
E
ia
As
Introduced
oysters have
vectored
many other
species
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?
Causes
• Why were Pacific oysters (Crassostrea
gigas) introduced to Washington State?
– Harvesting native oysters was no longer
economical… but therein lies a story
VANCOUVER
SEATTLE
Puget Sound
Willapa Bay
PORTLAND
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
The way it used to be? Willapa Bay at low water, late 1800s
Willapa Bay – current population between 0 and -2’ MLLW is sparse
in eelgrass
North Bay, Puget Sound – ~25 million oysters
between 0 and -4’, newly recovered
Washington Ostreola conchaphila Harvest
1.4E+05
1.2E+05
Willapa Bay
Puget Sound
Sacks
1.0E+05
8.0E+04
6.0E+04
4.0E+04
2.0E+04
0.0E+00
1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960
Trimble, unpubl.
Willapa Bay timeline
35
White fishers
Price/basket
30
200
25
150
20
15
100
10
50
5
0
0
1840
1850
1860
1870
1880
1890
1900
1910
Price $/basket
White population exploiting oysters
250
35
White fishers
Price/basket
30
200
25
150
20
100
15
First harvest restrictions
10
50
5
0
0
1840
1850
1860
1870
1880
1890
1900
1910
Price $/basket
White population exploiting oysters
250
35
White fishers
Price/basket
30
200
25
150
20
100
Native oysters described scientifically
15
10
50
5
0
0
1840
1850
1860
1870
1880
1890
1900
1910
Price $/basket
White population exploiting oysters
250
35
White fishers
Price/basket
30
200
25
150
20
Tideflat privatization
15
100
10
50
5
0
0
1840
1850
1860
1870
1880
1890
1900
1910
Price $/basket
White population exploiting oysters
250
35
White fishers
Price/basket
30
200
25
150
20
15
100
10
Marine Reserves
50
5
0
0
1840
1850
1860
1870
1880
1890
1900
1910
Price $/basket
White population exploiting oysters
250
Oyster Reserves:
•Legislated ~1900
•Almost perfect
overlap with original
native oyster beds
Collins, 1888
35
White fishers
Price/basket
30
200
25
150
20
15
100
10
50
C. virginica introduction
Subsequent introductions: 5
C. gigas - established
O. edulis
0
C. sikamea
C. ariakensis
0
1840
1850
1860
1870
1880
1890
1900
1910
Price $/basket
White population exploiting oysters
250
Commercial interest shifted to Crassostrea
gigas: Imports of spat to the west coast
120000
100000
Cases
80000
60000
40000
20000
0
1920
1930
1940
1950
1960
1970
1980
White, Ruesink, Trimble, unpubl.
Secondary production in Willapa Bay shifted from
native to non-native shellfish (filtration too)
Ruesink, Feist, Harvey, Hong, Trimble, Wisehart. 2006. Mar Ecol Prog Ser
Research efforts also shifted
35
30
Publications
25
20
Native
15
Introduced
10
5
0
<1930
1930-60
1960-80
• 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!
Has C. gigas functionally replaced
O. conchaphila?
• Native oyster
–
–
–
–
Brooding
Slow growth
Subtidal
Loose shell
• New oyster
–
–
–
–
Broadcasting
Rapid growth
Intertidal
Reef-building
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
Potential Factors Limiting Population Recovery
- Reproductive Failure (no)
----------------------- Settlement Habitat Change (yes)
- Pollution and Sedimentation (yes)
- Competition (space- yes)
- Predation (yes)
- Disease (limited)
Native oyster
recruitment
remains high
Long Island Reserve
Spatfall on
Cinder Block Anchors
(-10m)
Middle Sands Reserve
Quantitative recruitment time series
• Weekly records of spatfall from 19471987, 2002-2006
• Native oyster usually > Pacific oyster
1947-2006 Spatfall: O. conchaphila and C. gigas
100
O.conchaphila
C. gigas
90
Spat Per Shellface
80
70
60
50
40
30
20
10
0
1945
1965
1985
2005
But where do those larvae now settle?
What native oyster beds used to be… maybe… perhaps?
Settlement Habitat Change
C. gigas intertidal reefs
Settlement Habitat Change
Increased sedimentation from logging in watershed
Quantitative assessment of
recruitment across habitats
Recruitment rate across habitats
300
Recruits per 10 shellfaces
250
200
Most available habitat
Ostreola conchaphila
Above MLLW
Below MLLW
150
100
50
0
Shell
Bare
Habitat
Eelgrass
2-factor experiment: 3 elevations, +/- competitors
Tiles on mooring
Day 0 (1 month old)
Day 63
Day 304
“HIGH”
(+ 30cm)
MLLW
“LOW”
(- 30cm)
“MOORING”
(-1 m)
Survival declines when not submerged
F8,112 = 2.8, P = 0.007
Impacts of competitors
• Ectopleura crocea
• Botryllus spp.
• >45 introduced species
reported in Willapa Bay
Wonham & Carlton 2005 Biol Inv
Competitors Reduce Survival
F1,112 = 42.4, P < 0.001
Competitors Reduce Growth
F4,61 = 5.5, P = 0.001
Interactions between Washington’s native
and non-native oysters
Recruitment “sink”:
Intertidal aquaculture
Naturalized intertidal reefs
Recruitment, but poor
intertidal survival
Overgrowth?
Historical vector of
non-native predators
and competitors
-
High sustained
recruitment indicates
presence of core
reproductive
population
Bare
Gravel
Pacific shell
May 2004
Crushed Pacific shell
Native shell
Live natives
2
Recruit density (number per 0.0125 m )
18
A
16
Total
October live
April live
14
12
10
8
6
4
2
0
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Elevation (m MLLW)
B
2
Recruit density (number per 0.0125 m )
25
20
15
10
5
0
O.c. live
O.c. shell C.g. crushed C.g. shell
Substrate type
Gravel
Bare
Recruitment
improved at
lower
elevations
and on
natives
20
18
A
Count per shell
16
14
12
10
8
6
4
2
0
Rosette
Bag
Ground
B
Rogers
Nemah
Long Island
Mill Channel
40
Shell length (mm)
Shell
35
30
25
Rosette
Bag
Density: Low
High
Stable
Ground
Shell
Low
High
Unstable
Unstable treatments washed away
at most sites
Stable treatments were heavily
fouled at most sites
Rosettes – natives grew and
survived
Rosettes – buried at other sites
Shell on ground – not a functional
replacement for natives