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Presented by: Jay R. Leverone
Bay Scallop Population Dynamics within Two Southwest Florida Estuaries Following Restoration Practices Utilizing Competent Larval Releases Presented by: Jay R. Leverone
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PARTNERS Jay Leverone: Mote Marine Laboratory
Steve Geiger: Florida Fish & Wildlife Research Institute Bill Arnold: Florida Fish & Wildlife Research Institute Sarah Stephenson: Florida Fish & Wildlife Research Institute Curt Hemmel: Bay Shellfish Company Jaime Boswell: Sanibel-Captiva Conservation Foundation Norm Blake: University of South Florida Peter Clark:Tampa Bay Watch
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Florida Bay Scallop Populations
Stabilize Florida metapopulation by restoration of key coastal populations. Restoration began in Tampa Bay vicinity and progressed over time to estuaries further south. Florida Bay Scallop Populations
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History of Florida Bay Scallop Restoration Strategies
Direct Translocation of Native Stock from Stable Populations Planting of Hatchery-Produced Scallop Seed Release of Hatchery-Reared Scallop Larvae History of the first two strategies intermingled; originally transferred, then planted, then transferred from resurgent Anclote population Larval release strategy first applied to scallops in 2003
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Direct Translocation from Stable Populations
1972: Scallops transferred from Anclote to Tampa Bay and placed in cages to monitor thermal effects from a power plant (USF) 1980: Scallops translocated from Anclote to Mullet Key Bayou (USF) 1993: Steinhatchee to Sarasota Bay (MML) 1995: Steinhatchee to Tampa Bay (TBW) : Renewal of direct transplant from resurgent Anclote population (FWRI) 1972: Not restoration oriented. Mortality higher at thermally altered stations. Sublethal effects (disruption of normal reproductive cycle) at thermally altered stations. 1980: No cages? All scallops died in 6 weeks; no gonadal maturation; attributed to poor WQ 1993: 650 transplanted from Steinhatchee. Scallops survived through winter; spawning delayed or aborted. 1995: No followup. No results regarding survival, growth or reproductive status. 2002-5: 6,000 broodstock in cages. Part of a larger comprehensive program. Grew to reproductive size and spawned.
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Planting of Hatchery-Produced Scallop Seed
1991: Free release at two sites in Tampa Bay (USF) : Major restoration effort from Crystal River to Tampa Bay (FWRI) 1999: First scallop seeding effort in Sarasota Bay (MML) : Second, larger seeding project in Sarasota Bay (FWRI) 2004: Seven locations within Tampa Bay (FWRI) 1991: Cockroach Bay (10,000) and Mullet Key Bayou (1,000,000). Dispersed in mounds. Unable to relocate within hours of release : Comprehensive. Four sites; monitor growth, survival and reproductive development of planted scallops. Tested many options (cage type; habitat placement; densities). Caged scallops grew slower than wild counterparts; high mortality during late summer. Indications of success; genetics did not support. 1999: 26,000 seed scallops from USF. 50% mortality from a red tide in Feb. High mortality and biofouling during field deployments : Around 20,000 scallops planted over 2 years. Involved both cages and free planting. Rapid growth, high mortality; no evidence of recruitment. Another severe red tide in September, 2001. 2004: Part of the most recent comprehensive effort in Tampa Bay.
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Release of Hatchery-Reared Scallop Larvae
2003-present: Pine Island Sound, Lee County 2005-present: Mullet Key Bayou, Boca Ciega Bay, lower Tampa Bay Simple methodology. Key is obtaining healthy, viable larvae and proper acclimation from hatchery to field.
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Location of Tampa Bay and Pine Island Sound along the Florida west coast
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Larval release (●) and spat monitoring (▲) locations within each estuary
Orient audience to each estuary. Light grey represents seagrass meadows. TB ~ 20 sq. mi. of grass. PIS ~ 50 sq. mi. Spat monitoring throughout the estuary to monitor background recruitment
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Enclosure Setup
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Preparing Larval For Release
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Releasing Larvae and Monitoring Recruitment
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Release schedule for each estuary
LOCATION RELEASE DATE NUMBER OF ENCLOSURES NUMBER OF LARVAE/ENCLOSURE Pine Island Sound Pineland 1 10/28/2003 3 (Treatment) 1 (Control) 5.0 x 105 Pineland 2 10/03/2005 1 (Treatment) 1.2 x 106 Demere Key Powerline FWS Refuge 06/02/2006 Free release 4.0 x 106 Rabbit Key Basin 10/26/2006 1.3 x 106 Tampa Bay St. Antoine Key 04/07/2006 2 (Treatment) 7.5 x 105 Tarpon Key 12/21/2006 05/18/2007 West Mullet Key 10/25/2007 Cunningham Key Bonne Fortune Key Half million to over a million larvae per enclosure
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Spat settlement for each larval release
ESTUARY LOCATION RELEASE DATE MEAN NUMBER OF SPAT PER COLLECTOR NUMBER OF ENCLOSURES Inside Outside Pine Island Sound Pineland 1 10/28/2003 2.4, 1.8, 1.0 0.0 3 (control) 1 Pineland 2 10/03/2005 15.4 0.2 Demere Key 33.3 0.8 Powerlines 27.2 FWS Refuge 2.8 2.6 06/02/2006 ----- 0 (free release) Rabbit Key Basin 10/26/2007 Tampa Bay St. Antoine Key 04/07/2006 15.0, 13.4 2 Tarpon Key 3.2, 1.6 12/21/2006 6.4, 2.6 0.2, 0.4 05/18/2007 116.0, 77.2, 63.0 1.4, 0.6 West Mullet Key 10/25/2007 1 (+ free release) Cunningham Key Bonne Fortune Key Measure of recruitment success. Primary reason for using enclosures. Now combining enclosures with free-release.
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2003 Scallop Distribution Total = 28; Density = 1.4
Adult survey in June; Larval release in October of 2003. 2003 Scallop Distribution Total = 28; Density = 1.4
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Restoration Site Total = 63; Density = 160 2004 Scallop Distribution
Total at restoration site = 63. OR Density at site = 160/600 m2 vs 1.05/600 m2 at rest of area 2004 Scallop Distribution Total = 21; Density = 1.05
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2005 Scallop Distribution Total = 1,868; Density = 93.4
We did not see similar increases in the south 2005 Scallop Distribution Total = 1,868; Density = 93.4
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2006 Scallop Distribution Total = 163; Density = 8.15
Scallops more dispersed (found at 95% of stations). Density above the critical level of 5 set by FWC for transitional population. 2006 Scallop Distribution Total = 163; Density = 8.15
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Adult survey in June; Larval release in October of 2003.
2007 & 2008 Scallop Total = 0
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Scallop populations: South PIS
2004 2005 2006
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Recruitment of Scallops to Background Collectors in Pine Island Sound
Y axis reports average number of scallops per day. Large recruitment event in 2005 led to adult recovery that year Subsequent years had no recruitment
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Annual scallop abundance in Tampa Bay
YEAR 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 TBW 77 74 79 27 21 18 1 12 555 641 FWRI - TB ----- 2 106 740 FWRI - SB 2,499 TBW = Tampa Bay Watch “Great Bay Scallop Search” Volunteer Survey FWRI = Fish & Wildlife Research Institute Surveys
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Tampa Bay Scallop Distribution 2007 - 2008
2008 densities were 10x higher
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Recruitment of Scallops to Background Collectors in Tampa Bay
Scale is greater than PIS
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Differences in Scallop Population Dynamics Between Estuaries
Pine Island Sound Temporary resurgence in scallop abundance concurrent with 2003 restoration efforts 2005 restoration did not show similar response Recruitment limitation in the years following successful restoration led to population crash in 2007 Local scallop populations are likely isolated from other west Florida populations
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Differences in Scallop Population Dynamics Between Estuaries
Tampa Bay Recovery in scallop populations since 2007 coincides with larval release restoration activities Population recovery is also coupled with high recruitment rates in lower Tampa Bay Tampa Bay populations have maintained connectivity to adjacent coastal populations
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Implications for Future Restoration and Management Strategies
Need to monitor population dynamics in the smaller coastal embayments between Tampa Bay and Pine Island Sound Pine Island Sound may require multi-level restoration plan, while Tampa Bay can utilize spat collectors for long-term seeding Better understanding of water quality and harmful algal dynamics in Pine Island Sound will be required for ultimate recovery of scallops
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Funding and Support National Sea Grant
National Oceanographic and Atmospheric Administration Tampa Bay Estuary Program Sarasota Bay Estuary Program Florida Department of Environmental Protection National Fish and Wildlife Foundation (Pinellas County Environmental Fund) Charlotte Harbor National Estuary Program Ocean Trust Foundation South Florida Water Management District Mote Scientific Foundation
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