1. Evaluating Success of Oyster Restoration
Deriving Benchmarks
From Natural Populations
Hadley, N. H., L.D. Coen, V. Shervette, and M. Hodges

2. Success depends on your goals
Harvestable product
Ecosystem services
Public awareness
Sustainability may be an over-riding goal which applies to all

3. Evaluating Success Based on Goals
Harvestable oysters
Large percentage of market size oysters
This does not reflect natural populations patterns and may never be achievable
Ecosystem services
Many are difficult to measure
Develop at different rates
Habitat functioning may be inferred from presence of other species but does not necessarily depend on having oysters present
When can/should success be determined?
What constitutes success?
Multiple year classes
Size/density comparable to natural populations
How do you establish the targets?
Habitat functioning

4. Evaluating Success Based on Goals
Sustainability
When can/should success be determined?
Multiple year classes
Recruitment
Survival/growth
Size/density comparable to natural populations (convergence)
Retention of hard substrate for continued recruitment

5. Size Frequencies on 1 and 3 Year Old Reefs Fall 2004

7. Size/density comparable to natural populations
What’s your benchmark?
Reference reefs
Do they exist?
Are they “good”?
Long-term datasets
Mean values
Percentiles
What proportion of natural reefs are in “good” condition?
Classifying natural reefs along a continuum of “goodness”

8. Reference reefs

9. 70
Mean 50 30

11. 66% of reefs were fair or better
Overall Rating: Fair
27 Reefs were less than 3 years old at time of assessment.

12. Reefs sampled at 3 – 4 years

13. Alternative approach: Classify Natural Reefs

14. Strata E Excellent? Strata G Good Good Fair Strata C Fair
Strata A Very Good
Strata G Good
Good
Fair
Strata C
Fair

15. Very Good
Good
Fair
Poor

16. Characteristics of Natural Intertidal Oyster Populations in South Carolina
Few large oysters – usually less than 20%
High recruitment – usually 50% of populations
Mean size for all strata ranges from 25 – 35 mm
High variability within and among sites
High variability among years
A “good” reef one year may seem like a “poor” reef in another year

17. Establishing Success Benchmarks
What proportion of natural reefs are in “good” condition?
Very Good – 5% - Stratas A and E
Good – 37% - Stratas F and G
Fair – 38% - Stratas F1 and C
Poor -19% - Stratas D and W

18. Trask 3 Years Population means: Good Percentiles: Good
Strata G Good
Strata A Very Good
Population means: Good
Percentiles: Good
Strata convergence: Similar to G, may reach A

19. Palmetto 3 Years Population means: Good Percentiles: Good
Strata G Good
Strata A Very Good
Population means: Good
Percentiles: Good
Strata Convergence: Similar to A or E
Strata E Excellent? Or overcrowded

20. Dataw - 3 Years Population means: Fair Percentiles: Good
Strata G Good
Fair
Strata C
Population means: Fair
Percentiles: Good
Strata Convergence: Better than C, may reach G

21. 72% of planted area remained at the end of the study
77% of sites were fair or better
Overall Rating : Good

22. CONCLUSIONS
Size frequency of restored populations is useful for evaluating rate of development and sustainability.
Using natural population means or percentiles as targets may be striving for mediocrity.
Stratifying natural populations may provide more meaningful targets and allows us to examine development trajectories.
Success ratings for large and small-scale restored sites ranging in age from 3 to 6 years are similar regardless of which of these targets are used
Approximately 25% of restoration sites examined, both large and small scale, appear to be failures with little potential for development of sustainable populations of oysters.

23. Acknowledgements
Shellfish Research Section personnel who have measured thousands of oysters each year to generate this dataset.
All the volunteers who helped build and sample the reefs!
Funded by: