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A genetic assessment of Bay Scallop restoration in Bogue Sound, North Carolina
Sherman, M.1, D. Schmidt2, A.E. Wilbur1 1Department of Biology and Marine Biology, Center for Marine Science, University of North Carolina Wilmington, Wilmington, NC 28409 2 Goose Creek Rd. Newport, NC 28570
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Background Methods Results Conclusions
State of the scallop fishery in North Carolina Declining fishery likely due to several factors Red tide in 1987 Recruitment failure Predation Cownose rays Hurricanes low scallop abundance has prompted the investigation of restoration practices NC Scallops Landings ( ) recruitment failure following red tides in 87, several hurricanes in the 1990s and cownose ray predation.
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Background Methods Results Conclusions
Types of restoration strategies Preserve and protect Releases population from pressures Rebuild habitat Useful for substrate limited organisms Supplementation Transplantation Hatchery production Traditional hatchery practices Spawn, grow to size, and release Larval releases May be inexpensive and efficient Transplantation High probability of survival relative to other types. I wouldn’t make this claim as I have no data to suggest that this is true. What if stocks are locally adapted and the transplantation takes place between locations that aren’t compatible? What if transplantation is stressful? Easy to detect difference in abundance I’m not sure I understand this. Immediately following transplant there will indeed be more scallops, but is that restoration? Restoration is about rebuilding populations that persist and I don’t know that transplantation is any more easily assesed in the long term than any other strategy, unless the stocks are differentiated. Lowers abundance at source population Hatchery production Fairly confident that organism will survive Again, I know of no data that supports this once the animals are in the field. Expensive Difficult to produce large enough animals Larval releases Allows for greater dispersal Inexpensive Efficient Difficult to detect impact of release In general, you are indicating that we know a lot more about these strategies then I am aware of. It is not necessary to talk about the advantages and disadvantages of each, particularly since we don’t know what works and no one strategy is likely to be “best” in all circumstances. You are presenting a study that looks at a strategy that might work and if it does it saves time and effort and money. I think it would be sufficient to mention the range of approaches, mention that the first two depend on the assumption that remnant populations are healthy enough to recover…something that in NC doesn’t seem to be happening (fishery has been closed in recent years, new water quality rules implemented but still no scallops). Consequently supplementation may be needed (although we don’t have recent recruitment data that necessarily indicates limitation) and that larval releases are a possible strategy.
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Background Methods Results Conclusions
Larval releases in Florida- Pine Island Sound (Arnold 2008) In 2003, 1,500,000 larvae released from hatchery stock from 12 Anclote broodstock scallops In 2005, found an increase in abundance by a factor of 18 indicative of enhancement Retrospective genetic analysis Microsatellite analysis (9 loci) (Hemond 2006) Genotypes of broodstock not determined Broodstock source population (Anclote, FL) Pine Island scallops from before (2001) and after (2005) the 2003 larval release Could not confidently assign a source population Lack of differentiation between sources limits assignment success Jay Leverone releasing larvae in Pine Island Sound Log L (Pine Island source) Log L (Anclote source) Pine Island Sound Assignment Test Read Arnold 2008 and modify accordingly Read Liz’s thesis sections about assignment tests so that you understand how they work or go to Retrospective genetic analysis by Liz. Suggested several modifications Multiple larval releases allow for greater dispersal Containment booms may not be required if released at proper time Monitoring should adjust for greater larval dispersal Frequentist method (Praetkau et al. 1995) Based on probabilistic framework
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Background Methods Results Conclusions
Broodstock scallops are spawned Larvae are grown to the pediveliger stage Genetic signatures of broodstock and assessment scallops are compared to identify potential hatchery offspring Larvae are released into the wild Broodstock scallops are genetically characterized Spat and adult assessment scallops collected and genetically characterized
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Background Methods Results Conclusions
Fall A total of 85 wild scallops were collected for broodstock - Separated into five sets of broodstock
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Background Methods Results Future Implications
Before release spat traps were deployed surrounding the release site 6 traps placed feet from release site to be collected one month after deployment
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Background Methods Results Conclusions
Scallops were then introduced to the release site Healthy subtidal seagrass bed Low tide Limit vertical profile
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Background Methods Results Conclusions
Larval Release Summary Broodstock Location Age at larval release (days) Number of larvae Total larvae per site Red Taylor Bay 13 24 250,000 Green 11 17 1,000,000 Purple 14 12 154,000 1,404,000 Orange Piney Island 10 572,000 Yellow 9 15 515,000 1,087,000 Total 85 2,491,000 Releases took place in September and October 2007
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Background Methods Results Future Implications
June Scallops collected by snorkeling inside and outside of the deployment area Muscle tissue was extracted for genetic analysis Taylor Bay Piney Island
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Background Methods Results Conclusions
Genetic assessment to date: Mitochondrial DNA Sequencing of a 930bp region- 113/142 showed unique haplotypes 07 Wild scallops (N=57) 48 haplotypes (46 uniques) 07 Broodstock TB (N=53) 44 haplotypes (43 uniques) 07 Broodstock PI (N=32) 26 haplotypes (24 uniques) Overlap between broodstock and wild population before releases v v v
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Background Methods Results Conclusions
Genetic assessment to date Mitochondrial DNA In /57 (19.3%) wild scallops exhibited broodstock haplotypes In /265 (24%) assessment scallops exhibited broodstock haplotypes 08-Assessment PI 08-Assessment TB 07-Broodstock PI 07-Broodstock TB 07- Wild Scallops Mostly Haplotype 1 where overlap between broodstock and wild population greatest v
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Background Methods Results Conclusions
Microsatellite Analysis 5 loci to date Allele frequency plots suggest wild population and broodstock not differentiated AI115 AI131 AI327 g340 m26 07- Wild Scallops 07- Taylor Bay 07-Piney Island
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Background Methods Results Conclusions
Assignment test of potential source populations 25/57 wild correctly assigned to wild 18/85 broodstock scallops correctly assigned to hatchery Less than ½ of broodstock and wild scallops assigned correctly Assignment test shows limited separation, but as more microsatellites processed, increase statistical power, expect separation to become more distinct.
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Background Methods Results Conclusions
Assignment of assessment scallops Taylor Bay 41 mtDNA matches 22 assigned to broodstock released at Taylor Bay 2 assigned to broodstock released at Piney Island 17 assigned to wild population Piney Island 14 mtDNA matches 4 assigned to broodstock released at 10 assigned to broodstock released in Assignment not strong
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Background Methods Results Conclusions
Potential enhancement looks promising, but significant impact not detected with microsatellites to date 22/157 (~14%) properly assigned scallops in Taylor Bay 4/108 (~4%) properly assigned scallops in Piney Island Increased loci will likely increase the power to detect hatchery scallops Suggestions for future assessments Broader perspective Larval transport away from release site Broader geographic sampling Density survey Larval releases may work- how well? Are there more scallops?
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Acknowledgements NC Sea Grant Fisheries Resource Grant 06-EP-07
UNCW DNA Analysis Core Facility Bill Arnold (FFWRI), Skip Kemp (CCC), Tina Moore (NCDMF), Don Morlock Assignment test shows limited separation, but as more microsatellites processed, increase statistical power, expect separation to become more distinct.
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