Intersite and interspecific differences in rates of survival

Inter-site and inter-specific differences in rates of survival and growth of C. ariakensis and C. virginica: A collaborative on-bottom study in Virginia and Maryland Kingsley-Smith, P. R. , Harwell, H. D, Kellogg, M. L. , Allen, S. K. Jr. , Meritt, D. W. , Paynter, K. T. Jr. & Luckenbach, M. W. 9 th International Conference on Shellfish Restoration Charleston, South Carolina, USA November 15 th-19 th 2006

COLLABORATORS University of Maryland Center for Environmental Science (UMCES) Horn Point Laboratory FUNDING SOURCES

I. INTRODUCTION • Current knowledge of C. ariakensis survival and growth rates is based upon 1) field trials using triploids in off-bottom, caged aquaculture, and 2) quarantined studies using diploids. • Predicting rates of survival and growth of C. ariakensis in natural bottom habitats is critical to a pending decision on an intentional introduction. • Accurate determination of these rates will improve parameterization of a developing demographic model. • This study is the first to grow C. virginica and C. ariakensis (in VA and MD) side-by-side on the bottom in an effort to gather survival and growth data in a more naturalistic setting.

II. METHODS Triploid C. ariakensis and C. virginica were set on shell in May 2005 and planted at ~400 oysters m-2 in late Oct–Nov 2005 at 4 sites in VA and MD.

II. METHODS Oysters were planted in 2’ x 2’ bread trays in 5 x 5 arrays in late Oct-Nov 2005.

II. METHODS Machipongo River Virginia Cages were placed around the trays to prevent disturbances by large epibenthic predators (e. g. , cownose rays) and humans, while allowing access to small predators (e. g. , xanthid crabs).

II. METHODS Treatments (single treatment per cage): • C. virginica only • C. ariakensis only • C. virginica and C. ariakensis in a 50 : 50 mix • Shell only (no live oysters) Experimental design: • 2 replicate cages (blocks 1 and 2) per treatment (4) at each field site. • 4 sites (2 sites in Virginia; 2 sites in Maryland). • Sites were chosen to cover a range of salinities, water depths, disease pressures and relative predator abundances.

II. METHODS Delaware Severn River Bay Patuxent River Chesapeake Bay York River Machipongo River Atlantic Ocean 25 km

II. METHODS MACHIPONGO RIVER, VA Intertidal Salinity: ~30 psu Predation pressure: High Dermo & High MSX

II. METHODS YORK RIVER, VA Subtidal (1 -2 m) Salinity: 20 -25 psu Predation pressure: High Dermo & High MSX

II. METHODS PATUXENT RIVER, MD Subtidal (3 -4 m) Salinity: 8 -10 psu Predation pressure: Moderate Low Dermo & No MSX Courtesy of Paynter Lab SEVERN RIVER, MD Subtidal (3 -4 m) Salinity: 5 -8 psu Predation pressure: Low No Dermo & No MSX Courtesy of Paynter Lab

II. METHODS • Sampling = removal of 3 trays from each cage and replacement of sampled trays with those containing only clean shell. • Cages were sampled one month after deployment (i. e. , Nov-Dec 2005) to assess handling and early post-deployment mortality. • Quarterly sampling thereafter: Apr 2006, July 2006 and Oct 2006. • Future sampling: Apr 2007, July 2007 and Oct 2007.

II. METHODS This study will provide data on the following parameters: oyster survival (# live oysters) oyster growth (shell height mm) oyster biomass (ash-free dry weight) ploidy/reversion (biosecurity) disease (RFTM & histology) gametogenesis (histology) comparisons of habitat complexity between treatments (spp. ) and its relationship to associated free-living and attached faunal assemblages. (Poster by Heather Harwell et al. ).

II. METHODS This study will provide data on the following parameters: oyster survival (# live oysters) oyster growth (shell height mm) oyster biomass (ash-free dry weight) ploidy/reversion (biosecurity) disease (RFTM & histology) gametogenesis (histology) July 2006 comparisons of habitat complexity between treatments (spp. ) and its relationship to associated free-living and attached faunal assemblages. (Poster by Heather Harwell et al. ).

III. RESULTS – SURVIVAL 140 MACHIPONGO RIVER C. virginica C. ariakensis 120 100 Mean no. oyster tray -1 140 120 100 80 80 60 60 40 40 20 20 0 140 Oct Nov Dec Jan Feb Mar Apr May Jun Jul 2005 2006 PATUXENT RIVER 0 140 120 100 80 80 60 60 40 40 20 20 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul 2005 2006 YORK RIVER Single spp. cages only Error bars are S. D. s (n = 6) 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul 2005 2006 SEVERN RIVER Oct Nov Dec Jan Feb Mar Apr May Jun Jul 2005 2006

III. RESULTS – SURVIVAL - Within site comparisons 100 Error bars are S. E. s C. virginica C. ariakensis Mean # live oysters per tray 80 60 40 20 0 1 2 Machipongo 1 2 York 1 2 Patuxent 1 2 Severn

III. RESULTS – SURVIVAL - Within site comparisons 100 C. virginica C. ariakensis BLOCKS & SPP. NOT SIGNIFICANTLY DIFFERENT Mean # live oysters per tray 80 60 SIGNIFICANT BLOCK & SPP. EFFECTS 40 20 0 1 2 Machipongo 1 2 York 1 2 Patuxent 1 2 Severn

III. RESULTS – SURVIVAL - Within site comparisons 100 Error bars are S. E. s C. virginica C. ariakensis Mean # live oysters per tray 80 60 40 20 0 1 2 Machipongo combined York Patuxent Severn

III. RESULTS – SURVIVAL - Within site comparisons 100 Error bars are S. E. s C. virginica C. ariakensis Mean # live oysters per tray 80 60 40 ns 20 0 1 2 Machipongo combined York Patuxent Severn

III. RESULTS – SURVIVAL - Within site comparisons 100 Mean # live oysters per tray Subtidal C. virginica C. ariakensis 80 Error bars are S. E. s Intertidal 60 40 ns 20 0 1 2 Machipongo combined York Patuxent Severn

III. RESULTS – SURVIVAL - Within site comparisons 100 Mean # live oysters per tray 60 Subtidal C. virginica C. ariakensis 80 Error bars are S. E. s Intertidal MLW + 1 ft 40 ns 20 0 1 2 Machipongo combined York Patuxent Severn

Machipongo River Virginia

Machipongo River Virginia BLOCK 1

Machipongo River Virginia BLOCK 2

III. RESULTS – SURVIVAL - Within site comparisons 100 Mean # live oysters per tray 60 Subtidal C. virginica C. ariakensis 80 Error bars are S. E. s Intertidal MLW (p = 0. 06) MLW + 1 ft 40 MSX? predation? ns 20 0 1 2 Machipongo combined York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons 100 Error bars are S. E. s C. virginica C. ariakensis Mean # live oysters per tray 80 60 40 20 0 combined Machipongo York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons Error bars are S. E. s 100 C. virginica across site comparisons Mean # live oysters per tray 80 60 40 20 0 A AB BC C combined Machipongo York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons Error bars are S. E. s 100 C. virginica across site comparisons Mean # live oysters per tray 80 60 40 20 0 A AB BC C combined Machipongo York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons Error bars are S. E. s 100 C. virginica across site comparisons Mean # live oysters per tray 80 60 40 20 0 A AB BC C combined Machipongo York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons 100 Error bars are S. E. s increasing survival C. virginica across site comparisons Mean # live oysters per tray 80 60 decreasing salinity 40 20 0 A AB BC C combined Machipongo York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons Error bars are S. E. s 100 C. virginica across site comparisons Mean # live oysters per tray 80 60 Machipongo represents suitable habitat for C. virginica (survival comparable with York River)…. 40 20 0 A AB BC C combined Machipongo York Patuxent Severn

III. RESULTS – SURVIVAL – Across site comparisons Error bars are S. E. s 100 C. ariakensis across site comparisons Mean # live oysters per tray 80 …but less suitable habitat for C. ariakensis 60 40 b b b 20 0 a combined Machipongo York Patuxent Severn

III. RESULTS – GROWTH MACHIPONGO RIVER, VA JULY 5 TH 2006 YORK RIVER, VA JULY 24 TH 2006 # oysters C. virginica C. ariakensis PATUXENT RIVER, MD JULY 10 TH 2006 SEVERN RIVER, MD JULY 17 TH 2006 Shell height (mm) (Data include oysters from both single and mixed spp. cages. )

IV. CONCLUSIONS • Survival and growth data are now available for triploid C. ariakensis and C. virginica from several bottom habitats ranging in salinity, depth, disease pressure and relative predator abundance. • Significant interactions were observed between sites and species for both survival and growth. • Lowest survival of both species was observed at the intertidal Machipongo River site, with C. ariakensis survival especially low. • Highest growth rates of C. ariakensis were observed at the York River (site characteristics: subtidal & high salinity). • Both species (particularly C. virginica) show a trend of increased survival with decreasing salinity across sites. • Growth rates of C. virginica and C. ariakensis were most similar at the low salinity Severn River site.

V. ACKNOWLEDGEMENTS Eastern Shore Lab Reade Bonniwell PG Ross Sean Fate Alan Birch Edward Smith Jamie Wheatley Al Curry Stephanie Bonniwell Rochelle Brown University of Maryland (sampling help) Jake Goodwin Mark Sherman Steve Allen Marcy Chen Nancy Ward VIMS Shellfish Pathology Lab Ryan Carnegie Rita Crockett Susan Denny ESL Summer aides Raija Bushnell Sarah Mallette Matt Foley Andrew Wilson Andrew Matkin VIMS ABC Shane Bonnot Ryan Gill Karen Hudson

Pre-deployment shell height distributions 10 C. ariakensis C. virginica (mean SH = 13. 85 mm, n = 1272) (mean SH = 12. 80 mm, n = 1362) % frequency 8 6 4 2 5 10 15 20 25 shell height (mm) 30 35 40