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