west side story the context, causes, and consequences of the pacific oyster introduction to...
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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
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• 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.
Outline
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Context
• Oyster introductions have occurred frequently
• High establishment rate
• Vector for numerous other species
• Nearly complete replacement of native oyster production
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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 = ____
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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_
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When did oyster introductions occur?
0
20
40
60
80
100
120
1850 1870 1890 1910 1930 1950 1970 1990 2010
Cumulative number of transfers
Charles Elton fingered oyster introductions as the “greatest agency of all that spreads marine animals to new corners of the world”
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Where have oysters been introduced?
18
61
6
19
9
6
41
3
4
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Which oyster species have been introduced?
O’Foighil & Taylor 2000 Molecular Phylogenetics & Evolution 15:301
C. virginica = 16C. rhizophorae = 3
C. gigas = 64 + 6C. ariakensis = 3S. commercialis = 6S. cucullata = 3
O. edulis = 11
T. chilensis = 3C. densalamellosa = 1
O. conchaphila = 1O. puelchana = 1
C. echinata = 5C. sikamea = 3
C. iredalei = 2C. belcheri = 1
C. cortezensis = 1
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How well did they do?
0
10
20
30
40
50
60
70
C. gigasC. virginica
O. edulisC. angulata
S. commercialis
C. echinataC. ariakensisC. rhizophoraeC. sikameaS. cucullataT. chilensis
Frequency of locations
Unknown
Failed
Established
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Why were new oysters introduced?
• Replace native species
• Begin new product (Pacific islands)
• Research (12)
• Range expansion (4)
• By-product (3)
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Introduced oysters have replaced native oyster production
Africa W USA E USA CanadaS AmericaAustralia/NZEurope
Asia
10-year production 1993-2002(metric tons shucked)
0
1e+6
2e+6
3e+7
Introduced Native Uncertain
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Introduced oysters have
vectored many other
species
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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?
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Causes
• Why were Pacific oysters (Crassostrea gigas) introduced to Washington State?– Harvesting native oysters was no longer
economical… but therein lies a story
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VANCOUVER
SEATTLE
PORTLAND
Willapa Bay
Puget Sound
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Native oyster
Baker 1995
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
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The way it used to be? Willapa Bay at low water, late 1800s
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Willapa Bay – current population between 0 and -2’ MLLW is sparse in eelgrass
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North Bay, Puget Sound – ~25 million oysters between 0 and -4’, newly recovered
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Washington Ostreola conchaphila Harvest
0.0E+00
2.0E+04
4.0E+04
6.0E+04
8.0E+04
1.0E+05
1.2E+05
1.4E+05
1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960
Sacks
Willapa Bay
Puget Sound
Trimble, unpubl.
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1840 1850 1860 1870 1880 1890 1900 1910
White population exploiting oysters0
50
100
150
200
250
Price $/basket
0
5
10
15
20
25
30
35
White fishers Price/basket
Willapa Bay timeline
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1840 1850 1860 1870 1880 1890 1900 1910
White population exploiting oysters0
50
100
150
200
250
Price $/basket
0
5
10
15
20
25
30
35
White fishers Price/basket
First harvest restrictions
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1840 1850 1860 1870 1880 1890 1900 1910
White population exploiting oysters0
50
100
150
200
250
Price $/basket
0
5
10
15
20
25
30
35
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Native oysters described scientifically
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1840 1850 1860 1870 1880 1890 1900 1910
White population exploiting oysters0
50
100
150
200
250
Price $/basket
0
5
10
15
20
25
30
35
White fishers Price/basket
Tideflat privatization
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1840 1850 1860 1870 1880 1890 1900 1910
White population exploiting oysters0
50
100
150
200
250
Price $/basket
0
5
10
15
20
25
30
35
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Marine Reserves
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Collins, 1888
Oyster Reserves: •Legislated ~1900•Almost perfect overlap with original native oyster beds
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1840 1850 1860 1870 1880 1890 1900 1910
White population exploiting oysters0
50
100
150
200
250
Price $/basket
0
5
10
15
20
25
30
35
White fishers Price/basket
C. virginica introductionSubsequent introductions:
C. gigas - establishedO. edulisC. sikameaC. ariakensis
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Commercial interest shifted to Crassostrea gigas: Imports of spat to the west coast
1920 1930 1940 1950 1960 1970 1980
Cases
0
20000
40000
60000
80000
100000
120000
White, Ruesink, Trimble, unpubl.
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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
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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!
0
5
10
15
20
25
30
35
<1930 1930-60 1960-80
Publications
Native
Introduced
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Has C. gigas functionally replaced O. conchaphila?
• Native oyster– Brooding– Slow growth– Subtidal– Loose shell
• New oyster– Broadcasting– Rapid growth– Intertidal– Reef-building
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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
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Potential Factors Limiting Population Recovery
- Reproductive Failure (no)
-----------------------
- Settlement Habitat Change (yes)
- Pollution and Sedimentation (yes)
- Competition (space- yes)
- Predation (yes)
- Disease (limited)
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Middle Sands Reserve
Long Island Reserve
Spatfall onCinder Block Anchors
(-10m)
Native oyster recruitment
remains high
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Quantitative recruitment time series
• Weekly records of spatfall from 1947-1987, 2002-2006
• Native oyster usually > Pacific oyster
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0
10
20
30
40
50
60
70
80
90
100
1945 1965 1985 2005
Spat Per Shellface
1947-2006 Spatfall: O. conchaphila and C. gigas
O.conchaphilaC. gigas
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But where do those larvae now settle?
What native oyster beds used to be… maybe… perhaps?
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Settlement Habitat Change
C. gigas intertidal reefs
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Settlement Habitat Change
Increased sedimentation from logging in watershed
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Quantitative assessment of recruitment across habitats
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Recruitment rate across habitatsOstreola conchaphila
Habitat
Shell Bare Eelgrass
Recruits per 10 shellfaces
0
50
100
150
200
250
300
Above MLLW Below MLLW
Mos
t av
aila
ble
habi
tat
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2-factor experiment: 3 elevations, +/- competitors
Tiles on mooring
Day 0 (1 month old) Day 63 Day 304
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MLLW
(- 30cm)
(+ 30cm)“HIGH”
“LOW”
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“MOORING” (-1 m)
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F8,112 = 2.8, P = 0.007
Survival declines when not submerged
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Impacts of competitors
• Ectopleura crocea• Botryllus spp.• >45 introduced species
reported in Willapa Bay
Wonham & Carlton 2005 Biol Inv
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F1,112 = 42.4, P < 0.001
Competitors Reduce Survival
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F4,61 = 5.5, P = 0.001
Competitors Reduce Growth
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Interactions between Washington’s native and non-native oysters
Recruitment “sink”:Intertidal aquacultureNaturalized intertidal reefs
Historical vector of non-native predators and competitors
Recruitment, but poor intertidal survival
-
Overgrowth?
High sustained recruitment indicates presence of core reproductive population
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Bare Gravel Pacific shell
Crushed Pacific shell Native shell Live natives
May 2004
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Recruitment improved at
lower elevations
and on natives
A
Elevation (m MLLW)
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
Recruit density (number per 0.0125 m
2)
0
2
4
6
8
10
12
14
16
18
Total October live April live
B
Substrate type
O.c. live O.c. shell C.g. crushed C.g. shell Gravel Bare
Recruit density (number per 0.0125 m
2)
0
5
10
15
20
25
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A
Rosette Bag Ground Shell
Count per shell
0
2
4
6
8
10
12
14
16
18
20
B
Density: Low High Low High Stable Unstable
Rosette Bag Ground Shell
Shell length (mm)
25
30
35
40
RogersNemahLong IslandMill Channel
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Unstable treatments washed away at most sites
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Stable treatments were heavily fouled at most sites
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Rosettes – natives grew and survived
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Rosettes – buried at other sites
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Shell on ground – not a functional replacement for natives