Presentation on theme: "An ontogenic comparison of relative fecundity and egg quality of female Crassostrea virginica from northern Chesapeake Bay Hillary Lane 1 Vince Politano."— Presentation transcript:
An ontogenic comparison of relative fecundity and egg quality of female Crassostrea virginica from northern Chesapeake Bay Hillary Lane 1 Vince Politano 1, Stephanie Tobash-Alexander 2, Emily Vlahovich 2, Dr. Heather Koopman 3, Dr. Don Meritt 2, Dr. Ken Paynter 1 1 University of Maryland, College Park 2 University of Maryland Center for Environmental Science, Horn Point Laboratory 3 University of North Carolina Wilmington
Oyster Recovery Partnership (ORP) has been seeding natural and restored oyster bars with spat since 1997 Negligible natural recruitment Restored Maryland oysters are of known age +=
Synchronous broadcast spawning Fecundity measured as: Quantity of eggs ( with oyster size/age) Fertilization success ( with oyster size/age) What about egg quality ? Lets find out!
What is the relationship between oyster egg quantity and quality? How do these metrics vary with oyster age? Can these data help to determine an ideal age for hatchery broodstock and improve population sustainability?
200 oysters were collected per site Oysters were conditioned in flow-thru tanks at the Horn Point Oyster Hatchery for 2 weeks Magothy River: 4y & 11y Choptank River: 3y & 9y
100 animals per site were placed on spawning tables with ambient seawater (~20°C) Water temperature was increased at 5°C intervals for 1 hour Sperm was removed from males at each site and added to each spawning table once the water temperature reached 30°C
Spawning female oysters were immediately removed from the spawning table and placed in a 0.5L plastic tub to collect eggs Spent females were removed from tubs to collect metrics (shell height, mass, dry weight, P. marinus prevalence) Eggs were diluted to and counted by hatchery staff Eggs were filtered through 20µm sieves and frozen until lipid analysis
Total lipids were extracted using a modified Folch et al. (1957) chloroform:methanol technique Lipid content was determined as percent of wet tissue weight Lipid composition was determined using gas chromatography Fatty acids were quantified as percent composition
SiteAge# SpawnedMean Raw Count Chest Neck Dobbins States Bank Howell Point
No difference in egg count by oyster age, site or size
Dobbins oysters have more total lipid than other sites
Lipid content is driven by # of eggs produced, not oyster age BUT …
When separated by age, egg lipid content is only variable in OLD oysters
Egg fatty acid composition differs by age and site
Egg lipid content was associated with the number of eggs produced Oyster age may have affected the variation observed in egg lipid content Egg fatty acid composition varied by oyster age and site The differences found in egg quality may indicate differential allocation of resources by oyster age or location
Our data point to differences in egg lipid content and composition in oysters…so what?!?! Some measure of fertilization success or larval survival should be implemented to determine the ideal age/size oyster for broodstock These data may also help to identify target oyster sizes or ages for further successful management STAY TUNED!!!
University of Maryland College Park Horn Point Oyster Hatchery + Staff Oyster Recovery Partnership NOAA Chesapeake Bay Office Maryland DNR Steve Allen Karen Kesler Sara Lombardi Rebecca Kulp Grace Chon Drew Needham