Balancing Oyster Habitat Alterations with Coastal Wetland Restoration Activities in the Barataria Estuary Earl J. Melancon, Jr. Department of Biological Sciences Nicholls State University Thibodaux, LA 70310 U.S.A. ICSR 05 Brest, France October 2005
Louisiana New Orleans Study Area Gulf of Mexico Mississippi River
RESEARCH FOCUS Develop Management Guidelines so that Water Diversions and the Oyster Fishery can Co-exist We address this by asking: How have low-salinity events influenced the Oyster Fishery? Survival? Reproduction? Recruitment of spat? Shell growth Has there been any ecological event that caused negative impacts to oysters that were not associated with low salinity?
Cubic Feet per Second 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 Davis Pond Diversion Discharge Sept '03 to Sept '05 1 35 69 103 137 171 205 239 273 307 341 375 409 443 477 511 545 579 613 647 681 715 # Days
New Orleans Davis Pond River Diversion Nicholls State University Nicholls State University Bayou Lafourche Lake Salvador Little Lake 1 2 4 8 3 5 7 6 9 Barataria Bay 10 Mississippi River Mississippi River WITH-PROJECT 5-PPT LINE Gulf of of Mexico Base Map: USGS
Salinity (ppt) & Temp (C) 35 30 25 20 15 10 5 0 Bay DosGris Water Temperane & Salinity USGS LaHydrowatch D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A Salinity 2002 2003 2004 2005 2002 2003 2004 2005 Years by Months (2002-05) Water Temp Water Temperature and Salinity near Site 1 Continuous Recorder But look at summer 04 with low salinity All oysters Lived in Winter/Spring 04 as salinity decreased at site #1 Winter/Spring Low-Salinity Event Good Spring oyster spawn and spat set as salinity Increased in April 04 at site #1
30 25 20 15 10 5 0 Discrete Bottom Salinity Values April '04- July '05 4/15/2004 4/20/2004 5/10/2004 5/26/2004 6/10/2004 6/30/2004 7/12/2004 7/16/2004 8/5/2004 Do not disseminate 8/26/2004 without author authorization 9/28/2004 10/28/2004 12/13/2004 2/15/2005 3/24/2005 4/5/2005 4/21/2005 5/18/2005 6/14/2005 6/29/2005 7/14/2005 Summer 04 All oysters Died in Summer 04 at sites #1 and #6 and only @ 25 % died at site #9 Excellent Fall spat set all sites; from oyster metapopulations elsewhere in estuary WHY NOT SUCCESSFUL? Site 1 Site 6 Site 9 Low April 05 Salinity and only partial Spawn occurred; very poor spat set in May-June Although salinities were good for larvae and Spat survival Salinity (ppt)
Secchi Depth (cm) 180 160 140 120 100 80 60 40 20 April to June 05 Events April = not enough high-salinity time for substantial gonad development? May to June = Food crash for larvae and spat? 0 Barataria Bay Water Clarity 4.6 ft visibility May June July Month 2004 2005
Shell Length 160 140 120 100 80 (mm) 60 40 20 0 ideal seed length BB-4 Up-Estuary Growth of Tagged Oysters Sept '04 to August ' 05 Spat to Seed Seed to Sack Site BB-8 Dow n-estuary acceptable sack length
SUMMARY (Preliminary) Salinity < 5ppt is OK in cooler months, November-March for oyster survival. Salinity must remain > 5ppt April-October for oyster survival, reproduction, and recruitment. Spring larvae and spat survival closely tied to higher salinity in May-June and availability of food in water. Bay has potential to become an annual fall seed crop for bedding elsewhere, if follow above recommendations. Bay has potential to become a bi-annual sack fishery, if follow above recommendations. There will always be a risk factor for oyster mortalities since management can not predict acts of nature. * * But oystermen s investment risks can be reduced if understand general weather patterns, e.g., wet El nino years best to harvest as a seed.
Dr. Earl Melancon w ith ou ta ut ho ra ut ho riz at io n Members of the Research Team Nick Gaspard se m in at e Dr. Allyse Ferrara D o no td is Ronnie Duke Cassie Addison Dr. Badiolah Asrabadi
ACKNOWLECTEMENTS Barataria Bay Oystermen Louisiana Oyster Task Force Louisiana Sea Grant through National Sea Grant s Gulf Oyster Industry Initiative Program (GOIP) BP America, Inc. Many undergraduate Marine Biology Students Nicholls State University Administration
Barataria Bay Hurricane Katrina August 28, 2005
Lake Ponchartrain New Orleans Barataria study area St. Louis Bay Louisiana's Primary Public Oyster Grounds Breton Sound Town of Empire Chandeleur Islands path
Empire Marina is Destroyed Home to a significant part of Louisiana Oyster fleet
Town of Empire Boats on Levee
Chandeleur Islands Before and After
Town of Waveland Southwest of St. Louis Bay Before and After Trees Defoliated
Town of Pass Christian Marina Destroyed Home of the Mississippi Oyster Fleet East of St. Louis Bay
at io n ho riz ra ut ho ut ta ou ith w e in at se m is td no o D Town of Bay St. Louis Only house slabs remain
at io n ho riz no o D Flooded Homes To rooftops td is se m in at e w ith ou ta ut ho ra ut 17th Street Levee Breach in New Orleans Lake Ponchartrain
Our Research Sites in Barataria % mortality 100 80 60 40 20 0 Central Barataria Bay Oyster Mortalty Pre and 2-Weeks Post Hurricane Katrina All Shell Lengths Represented 18-Jul-05 1 2 3 4 5 6 7 8 9 10 Site 13-Sep-05 AND CONTINUING TO DIE from mud and grass burial
Thank You