|
|
|
Abstracts
Workgroup: Oyster Fisheries Management and Restoration
Environmental effects on Perkinsus marinus infection rates, growth and survival among dermo-disease-free juvenile oysters planted at three salinity regimes in an enzootic Chesapeake Bay Oyster Recovery Area
Principal Investigator(s):
George Abbe, Academy of Natural Sciences Estuarine Research Center, abbe@acnatsci.org
Co-Investigator(s):
Chris Dungan and Steve Jordan, Sarbanes Cooperative Oxford Laboratory
Funding Period: Jan. 1, 2000 - Dec. 31, 2001
Specific pathogen-free (SPF) oysters were set on oyster shell and transplanted to three sites on natural oyster bars in the Patuxent River, Maryland along a salinity gradient to investigate environmental effects of Perkinsus marinus on infection rates, growth and survival. Spat were deployed at each site for disease monitoring, and 100 were followed for growth and mortality. From September 2000 to September 2001salinities at Holland Point (HP, upper river), Gatton (GAT, mid) and Town Creek (TC, lower) averaged 11.1, 13.0 and 14.4, respectively. Oysters were examined monthly for growth and mortality and 30 were collected from each site for assay of P. marinus infections by the whole body burden technique. This allowed determination of time to initial infection and subsequent progression of dermo disease reflected by parasite burdens. An additional 30 from the natural population at each site were also examined monthly by rectal tissue assay.
Oysters (initially 25 mm) at HP, GAT and TC grew 23, 34 and 27 mm, respectively, and survival was 95, 98 and 94% during the first 12 months. Three discrete spat sets and deployments were made: September 2000, June 2001, and August 2001. Animals at sites TC and GA September 2000 deployments acquired P. marinus infections within 2 weeks, with prevalences of 10% and 3% respectively. Positive results at low prevalences and intensities continued for 8 weeks. Sites TC and GA June 2001 deployment acquired infections within 2 weeks, with 10% and 13% prevalences respectively, and positive results continued for 8 weeks with increasing prevalences. Site HP acquired one infection (3%) between 2 and 4 weeks. Positive results continued through two additional 4-week sampling intervals, with increasing prevalences. All August 2001 deployments acquired infections within 2 weeks, with prevalences of 7%, 87%, and 3% respectively, and positive results continued for 8 weeks. Infection intensities among these samples ranged from 1-23 hypnospores per host animal. The GA site was 100% infected by 8 weeks post-deployment. These results show that juvenile oysters acquire Perkinsus marinus infections as early as 2 weeks after placement in dermo-disease endemic areas, and that these infections persist in the planted populations over time.
Mean intensity of dermo disease among feral populations (on a scale of 0-7) at HP, GAT and TC ranged from 1.1 to 4.2, 0.7 to 4.6 and 0.7 to 4.7, respectively, and averaged 2.51, 2.72 and 2.79. It appears that salinity, varying within the range of our sites, had little effect on growth, survival or infection intensity during the first year.
IMPACTS and/or BENEFITS:
There was little impact evidenced from the first year of this study other than development of our overall strategy and techniques that was to carry over into year 2 and 3. Preliminary data suggested that a mid-river site might be the best area to locate oysters, but additional data during subsequent years dictated otherwise.
PROJECT PUBLICATIONS:
George R. Abbe, Brian W. Albright, Carol B. McCollough, Christopher F. Dungan and Stephen J. Jordan. 2002. Environmental effects on Perkinsus marinus infection rates, growth and survival among dermo-disease-free juvenile oysters planted at three salinity regimes in the Patuxent River, Maryland. Journal of Shellfish Research 21:371. (This was also an invited paper presented at the National Shellfisheries Association meeting in Mystic, Connecticut in April 2002.)
Carol B. McCollough, Christopher F. Dungan, Stephen J. Jordan, George R. Abbe and Brian W. Albright. 2002. Perkinsus marinus infection rates in specific-pathogen-free juvenile oysters planted at three salinity regimes in the Patuxent River, Maryland. Journal of Shellfish Research 21:375. (An invited paper presented at the National Shellfisheries Association meeting in Mystic, Connecticut in April 2002.)
![[Maryland Sea Grant]](../mdsg_logo.gif){kind=logo}
![[NOAA]](../noaa_logo.gif){kind=logo}
![[Virginia Sea Grant]](../vasg_logo.gif){kind=logo}