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Abstracts
Workgroup: Public Health and Processing
Response of the Hooked Mussel, Ischadium Recurvum, to Relaying as a Remediation Technique to Reduce Biofouling on Oysters and Documentation of its Distribution in a Louisiana Estuary
Principal Investigator(s):
Earl J. Melancon, Jr., Biology Department, Nicholls State University, Thibodaux, LA, Earl.Melancon@nicholls.edu
Co-Investigator(s):
Badiollah Asrabadi, Nicholls State University
Dale Diaz, Mississippi Department of Marine Resources.
Dale Diaz, Mississippi Department of Marine Resources.
Funding Period: 1999-01(extension to end of 2002)
Results indicate the following: (1) An abrupt change from a low salinity to a high salinity environment by transplanting to a new site is of minimal physiological stress to mussels, and therefore of minimal influence on their removal from oysters, (2) Predation is the driving force on the removal of mussels from oysters. Predators, such as blue crabs, oyster drills, and fish (primarily sheepshead and black drum), dominated in this study. Predator abundance is predominantly a function of salinity, with higher salinity environments generally having more predators, (3) The physical process of harvesting with a dredge, pushing oysters to the rear of the deck using water cannons, and pushing oyster overboard with water cannons at the new transplant site, resulted in 33-38% of the mussels being crushed or dislodged from the oysters; The dead and dying mussels attracted predators, (4) In two June-July commercial-scale transplanting operations, one to a mid-bay (moderate-salinity) site and the other to a down-bay (high-salinity) site, predators had effectively removed enough mussels for re-harvest within five to eight days after bedding, (5) Evaporative cooling and the use of water cannon kept deck temperatures within the tolerance range for both species; summer transplanting did not reduce oyster meat yield, (6) Mussels are more abundant on oysters in low-salinity (up-bay) environments because of reduced predator abundance, (7) Mussels have a lower salinity tolerance than oysters; Monitoring oyster reefs for 20-months indicated that mussels can survive an oyster-killing freshet during summer water temperatures with salinities as low as 1ppt, and (8) Mussels were spawning and their larvae were setting between April and October.
IMPACTS and/or BENEFITS:
To improve relaying success, the following is recommended to commercial oystermen: Planting to mid-bay and down-bay habitats will remove mussels within a short period of time if predators are present; Perhaps in as little as a week during summer water temperatures. At a mid-bay transplant site, where salinities are moderate, a simple check with crab fishermen may be beneficial to determine if blue crabs are in abundance, the primary mussel predator in this study. At a down-bay transplant site where higher salinities prevail, many species of predators are usually abundant, except perhaps during a wet period. A high-salinity (down-bay) transplant site may require a quicker re-harvest time than an up-bay site because of oyster predator abundance. Transplant operations that use water cannon suppress temperatures within the pile of oysters and mussels on deck and thereby allowing transport during summer months without harming oysters. Additionally, keeping a lease cultivated by breaking up oyster clusters reduces mussel fouling in mid-bay and down-bay sites. Throughout the study it was evident that in mid-to-high salinity subtidal environments the only mussels that survived were associated with clustered (bunchy) oysters that provided shelter in the crevasses. At up-bay (low-salinity) sites, cultivation and breaking of oyster clusters was not a significant deterrent to mussel fouling.
PROJECT PUBLICATIONS:
No referred journal publications have been generated by this research; Publications are in
preparation for submittal. Four (4) presentations at national and regional conference.
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