Role of oyster age vs. oyster size in determining sex ratios on restored oyster reefs in Chesapeake Bay M. Lisa Kellogg, Marcy E. Chen, Victor S. Kennedy, C. Paul Miller, Sara E. Rowland, Richard T. Paynter, Kennedy C. Paynter, Nancy J. Ward, Dawn Goldsmith, Mark W. Sherman, Jacob D. Goodwin, Christopher P. McIntyre, Steven Allen and Kennedy T. Paynter

Oyster Reef Restoration in Maryland: Oyster Recovery Partnership coordinates oyster reef restoration efforts in MD portion of Chesapeake Bay MDNR, MD Watermen’s Association, ACOE, UMD and various NGOs (e.g. CBF) In recent years, sanctuaries and managed reserves have been planted annually in Maryland Sanctuaries focus on ecological restoration Managed reserves focus on fishery rehabilitation Almost all spat are produced from wild stock at HPL Planted as spat on shell Planted in discrete year classes (i.e. same location rarely planted in subsequent years)

Sex Ratios in Oyster Populations: Oysters are protandric Generally male when they first mature Proportion of females increases with increasing age/size Previous studies found a greater proportion of females associated with: Increasing distances between individuals (Burkenroad 1931) Single oysters vs. clumps (Smith 1949) Settlement on shell vs. settlement on adult oysters (Menzel 1951)

Questions: What are the sex ratios of oysters on planted reefs in MD? Do they exhibit the same patterns as previously studied populations? What can sex ratio patterns on plantings tell us about possible factors influencing sex ratio patterns of oysters in general? What are the implications for oyster reef restoration efforts?

Questions: What are the sex ratios of oysters on planted reefs in MD? Do they exhibit the same patterns as previously studied populations? What do sex ratio patterns on plantings tell us about possible factors influencing sex ratio patterns of oysters in general? What are the implications for oyster reef restoration efforts?

Oyster Reef Restoration in Maryland: Unique opportunity to examine the relationship between sex ratio and oyster age and/or size in the field All oysters sampled have similar history Spat on shell from HPL Hatchery Known planting dates Monitoring records show that there has been no significant natural recruitment Estimates of oyster age are not confounded No need to use oyster size as a proxy for oyster age

Sampling Sites: Magothy River Chester River Choptank River Chest Neck Point - 2001 Chester River 13 sites Choptank River 12 sites

Chester River: Boathouse Emory Hollow Devil’s Playground Strong Bay Blunts Devil’s Playground Chester River: Boathouse 2005 Emory Hollow 2001, 2002, 2004 Devil’s Playground Strong Bay 2003 (2), 2004, 2005 Blunts 2002, 2003, 2005 (2)

Choptank River: Howell Point Green Marsh Shoal Creek Bolingbroke Sand Mill Dam Dixon The Black Buoy Bolingbroke Sand Shoal Creek Green Marsh Howell Point Choptank River: Howell Point 2001 Green Marsh 2003 Shoal Creek 2001, 2004, 2005 Bolingbroke Sand 2002, 2003, 2005 The Black Buoy 2004, 2005 Dixon 2005 Mill Dam

Field Sampling: Quadrat grabs by divers Goal: Actual: 30 cm x 30 cm quadrat = 0.09 m2 All shell material in quadrat collected Goal: Minimum of 50 oysters/site Minimum of 3 quadrats/site Actual: 39 – 291 oysters collected/site 3 – 22 quadrats collected/site 2214 oysters collected in total

Sample Processing: All oysters collected were individually labeled Data collected: Shell height (mm) of all oysters Distances between the ventral shell margins of all oysters in each clump Sex of all oysters determined by microscopic examination of gonad smears

Resulting Data: Individual oyster sex Individual shell heights Planting year # of oysters/quadrat # of oysters/clump # of single oysters Distance to nearest neighbor Distance to nearest neighbor of opposite sex

Resulting Data: Individual oyster sex Individual shell heights Planting year # of oysters/quadrat # of oysters/clump # of single oysters Distance to nearest neighbor Distance to nearest neighbor of opposite sex

“Natural” Oyster Bars

All Oysters – All Sites

All Oysters – All Sites

1 Year After Planting

2 Years After Planting

3 Years After Planting

4 Years After Planting

5 Years After Planting

“Natural” Oyster Bars

Low n for Largest Size Classes

Future Directions: Detailed analysis of all current data Determine influence of other measured factors (e.g. # of oysters/quad, average distance to nearest neighbor, etc.) Include more info on planting history (e.g. density at time of planting, growth rates, mortality rates, disease history) Formulate testable hypotheses about factors driving observed patterns Additional data collection in 2007: Target bars with older plantings to increase the sample sizes in the larger size classes Sampling of “natural” oyster bars in vicinity of plantings

Charlie Frentz, Director “Mutt” Meritt and Hatchery Crew Acknowledgements: Oyster Recovery Partnership Charlie Frentz, Director “Mutt” Meritt and Hatchery Crew