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

Outline Context Causes Consequences 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_

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”

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

Which oyster species have been introduced? C. virginica = 16 C. cortezensis = 1 C. rhizophorae = 3 C. echinata = 5 C. gigas = 64 + 6 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

How well did they do?

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

Introduced oysters have replaced native oyster production

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

Trimble, unpubl.

Willapa Bay timeline

First harvest restrictions

Native oysters described scientifically

Tideflat privatization

Marine Reserves

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

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

Commercial interest shifted to Crassostrea gigas: Imports of spat to the west coast 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 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? New oyster Broadcasting Rapid growth Intertidal Reef-building Native oyster Brooding Slow growth Subtidal Loose shell

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 1947-1987, 2002-2006 Native oyster usually > Pacific oyster

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

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 Most available habitat

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? High sustained recruitment indicates presence of core reproductive population Historical vector of non-native predators and competitors -

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

Recruitment improved at lower elevations and on natives

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