quality vs. quantity
DESCRIPTION
QUALITY VS. QUANTITY. 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 , - PowerPoint PPT PresentationTRANSCRIPT
QUALITY VS. QUANTITYAn ontogenic comparison of
relative fecundity and egg quality of female Crassostrea virginica from northern Chesapeake Bay
Hillary Lane1
Vince Politano1, Stephanie Tobash-Alexander2, Emily Vlahovich2,Dr. Heather Koopman3, Dr. Don Meritt2, Dr. Ken Paynter1
1University of Maryland, College Park2University of Maryland Center for Environmental Science, Horn Point Laboratory
3University of North Carolina Wilmington
Oysters in the Chesapeake Bay
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
“Seasonal year” data (include data from the winter harvest and the preceding year's fall harvest).Data and Methods: www.chesapeakebay.net/status_oysterharvest.aspx
BushelsChesapeake Bay Commercial Oyster Harvest
Oyster Restoration in Maryland
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
+ =
C. virginica Reproduction Synchronous broadcast spawning Fecundity measured as:
Quantity of eggs ( with oyster size/age) Fertilization success ( with oyster size/age)
What about egg quality?
Let’s find out!
RESEARCH QUESTIONS
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?
Methods: Sample Collection
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
Methods: Spawning 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
Methods: Egg Collection 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 30-30 and counted by hatchery staff
Eggs were filtered through 20µm sieves and frozen until lipid analysis
Methods: Lipid Extraction and 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
Results: Standard MetricsSite Age # Spawned Mean Raw Count
Chest Neck 4 20 355
Dobbins 11 4 104
States Bank 3 32 332.9
Howell Point 9 41 296.5
Chest Neck Dobbins States Bank Howell Point0
0.20.40.60.8
11.21.4
P. Marinus prevalanceP. marinus weighted prevalance
P. m
arin
us v
alue
Chest Neck Dobbins States Bank Howell Point0
20
40
60
80
100
120
140
Shel
l Hei
ght
(mm
)
Chest Neck Dobbins States Bank Howell Point0
0.5
1
1.5
2
2.5
Dry
Wei
ght
(g)
Results: Egg Count
Tran
sfor
med
Raw
Cou
nt
0
5
10
15
20
25
30
35
Chest Neck Dobbins Howell Point States Bank
Site
Tran
sfor
med
Raw
Cou
nt
0
5
10
15
20
25
30
35
Old Young
Age Class
0
5
10
15
20
25
30
35
Tran
sfor
med
Raw
Cou
nt
60 70 80 90 100 110 120 130 140 150Shell Height (mm)
No difference in egg count by oyster age, site or size
Results: Egg Lipid Content%
Lip
id
0
1
2
3
4
5
6
7
Old Young
Age Class
% L
ipid
0
1
2
3
4
5
6
7
Chest Neck DobbinsHowell Point
States Bank
Site
Each PairStudent's t 0.05
Dobbins oysters have more total lipid than other sites
Results: Egg Count + Lipid Content
0
1
2
3
4
5
6
7
% L
ipid
5 10 15 20 25 30 35Transformed Raw Count
0 5 10 15 20 25 30 350.0
1.0
2.0
3.0
4.0
5.0
6.0
Chest NeckDobbinsHowell PointStates Bank
Transformed Raw Count
Tota
l Per
cent
Lip
id
Lipid content is driven by # of eggs produced, not oyster ageBUT…
Results: Egg Count + Lipid Content by Age
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.000.0
1.0
2.0
3.0
4.0
5.0
6.0 Chest NeckDobbinsHowell PointStates Bank
Transformed Raw Count
Tota
l Per
cent
Lip
id
5.00 10.00 15.00 20.00 25.00 30.00 35.000.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0DobbinsHowell Point
Transformed Raw Count
Tota
l Per
cent
Lip
id
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.000.0
1.0
2.0
3.0
4.0
5.0
6.0 Chest NeckStates Bank
Transformed Raw Count
Tota
l Per
cent
Lip
id
When separated by age, egg lipidcontent is only variable in OLD oysters
Results: Egg Fatty Acid Composition
Egg fatty acid composition differs by age and site
Conclusions 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
The Perfect Broodstock Animal? 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!!!
Acknowledgements 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