Benthos Ecology
http://hdl.handle.net/10793/1191
2024-03-28T22:07:00Z
2024-03-28T22:07:00Z
Preliminary recruitment studies of the eastern oyster, Crassostrea virginica, and their potential applications, in coastal Georgia
O'Beirn, F.X.
Heffernan, P.
Walker, R.L.
http://hdl.handle.net/10793/1275
2019-08-30T08:39:12Z
1995-01-01T00:00:00Z
Preliminary recruitment studies of the eastern oyster, Crassostrea virginica, and their potential applications, in coastal Georgia
O'Beirn, F.X.; Heffernan, P.; Walker, R.L.
Oyster recruitment was monitored in Wassaw Sound, Georgia from April through October, 1991. The study was initiated to determine precise recruitment patterns of oysters over the 7 month spawning season. One of the goals was to determine the most suitable time for the collection of natural spat for maricultural, fisheries and recreational purposes. Three sites of varying hydrographic characteristics were chosen in Wassaw Sound. The sites varied in terms of temperature and salinity regimes and in their exposure to wind and wave action. Within each site, oyster recruitment was estimated at three tidal heights; subtidally, at mean low water and intertidally, approximately 2 h above the mean low water mark. Sampling took place so as to measure net recruitment over biweekly (BW), monthly (M) and seasonal ( S) periods. The results indicated that the recruitment of oysters in this region of coastal Georgia is protracted, lasting 6 months (May through October). The levels of recruitment were very high relative to other regions on the east coast of the USA, with peak recruitment for the entire study area (x = 2800 spat m- 2 for BW and x = 3020 spat m- 2 for M) occurring between July and September. The intensity of recruitment varied significantly among the three sites. The most sheltered site in terms of wave exposure experienced the highest recruitment (x =4380 spat m- 2 BW; x = 6260 spat m -2 M). This site also had higher overall water temperatures as well as greater daily temperature fluctuations. The least sheltered site had the lowest numbers of young oysters (x = 1000 spat m- 2 BW; X. = 686 spat m- 2 M), as well as having the most stable temperature regime. The biweekly samples generally experienced higher recruitment subtidally at the three sites. The monthly samples had higher numbers of oyster spat at the mean low water mark while the seasonal samples showed significantly higher recruitment intertidally (up to x =7353 spat m-2 ). The shift in recruitment patterns over time is partially attributed to increased subtidal predation pressure on the recruits. The collection of natural spat in relation to the natural fishery, potential maricultural activity and the recreational fishery is discussed.
Peer-reviewed.
1995-01-01T00:00:00Z
Reproductive biology and parasite (Perkinsus marinus) prevalence in the eastern oyster, Crassostrea virginica, within a Georgia tidal river
O'Beirn, F.X.
Walker, R.L.
Jansen, M.L.
http://hdl.handle.net/10793/1240
2019-08-30T08:39:11Z
1997-01-01T00:00:00Z
Reproductive biology and parasite (Perkinsus marinus) prevalence in the eastern oyster, Crassostrea virginica, within a Georgia tidal river
O'Beirn, F.X.; Walker, R.L.; Jansen, M.L.
Recruitment, in 1992, of the eastern oyster, Crassostrea virginica, at one site (Flume Dock) within the Sapelo Island National Estuarine Research Reserve (SINERR) was lower than other sampling sites. Recruitment allied with gametogenesis and parasite (Perkinsus marinus) prevalence within the oysters was examined in 1993, in an attempt to explain the differences observed the previous year. Sampling occurred at three sites (Marsh Landing, Jack Hammock, and Flume Dock) along the Duplin River within the SINERR. Oyster recruitment in 1993 was reduced in all sites within the SINERR. No oyster recruitment was recorded at the Flume Dock site during any monthly collections or on collectors deployed for the duration of the sampling study. Oysters developed gametogenically and spawned at the Marsh Landing site two weeks prior to their occurrence at the
Jack Hammock site. Gametogenic development in oysters at the Flume Dock site was retarded a further two weeks where the males appeared to spawn six weeks after the females, which could account for reduced recruitment levels at this site. Approximately, twice as many females as males occurred in all sites. Monthly sampling of prevalence and intensity of Perkinsus marinus (Dermo) revealed high levels of both parameters. Smaller oysters did display lower prevalences of Dermo than larger forms.
Peer-reviewed. © F.X. O'Beirn et al., 1997. Reproduced with the permission of the executive editor of the JNCAS.
1997-01-01T00:00:00Z
Survival and growth of juvenile freshwater mussels (Unionidae) in a recirculating aquaculture system
O'Beirn, F.X.
Neves, R.J.
Steg, M.B.
http://hdl.handle.net/10793/1238
2019-08-30T08:39:11Z
1998-01-01T00:00:00Z
Survival and growth of juvenile freshwater mussels (Unionidae) in a recirculating aquaculture system
O'Beirn, F.X.; Neves, R.J.; Steg, M.B.
An indoor recirculating aquaculture system was constructed to provide suitable conditions to culture juvenile freshwater mussels. In the first of three growth trials, Villosa iris (I. Lea, 1829) juveniles were cultured for 22 wk, and grew from an initial mean length of 0.4 mm to 2.7 mm. Survival was 26.8% overall. In the second trial, growth and survival were compared between juveniles of V. iris held in sediment and without sediment. The initial mean length of both groups was 2.7 mm, and this experiment ran for 17 wk. The juvenile mussels in sediment grew to a mean length of 5.7 mm with 85% survival, significantly greater (p < 0.01) than juveniles held without sediment (4.5 mm, 74% survival). In the third trial, two cohorts of juvenile Lampsilis fasciola Rafinesque, 1815, increased in length from I.I mm and 1.4 mm to 3.3 mm and 4.1 mm, respectively, with comparable survival (78.7% versus 64.5%). Results of these trials demonstrate that juvenile mussels can be reared successfully within recirculating systems. One of the factors deemed important in successful culture is continuous feeding of an appropriate food source. In this study, a unialgal culture of Neochloris oleabundans Chantanachat and Bold, 1962, was used throughout. Regular cleaning of the system and water replacement also was important. Finally, the culture of juveniles in sediment appears to be an important factor in ensuring good growth and survival. This phenomenon could be related to pedal feeding behavior, proper orientation of the mussels for filtering efficiency, or stability from physical disturbance.
Peer-reviewed. Copyright © 1998 F.X. O'Beirn et al. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-ShareAlike License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1998-01-01T00:00:00Z
Prevalence of Perkinsus marinus in the eastern oyster, Crassostrea virginica in relation to tidal placement in a Georgia tidal creek
O'Beirn, F.X.
Dean, C.C.
Walker, R.L.
http://hdl.handle.net/10793/1236
2019-08-30T08:39:11Z
1994-01-01T00:00:00Z
Prevalence of Perkinsus marinus in the eastern oyster, Crassostrea virginica in relation to tidal placement in a Georgia tidal creek
O'Beirn, F.X.; Dean, C.C.; Walker, R.L.
This experiment was designed to evaluate the effects tidal zonation and bottom placement of the eastern oyster, Crassostrea virginica, have on the prevalence and intensity of the oyster parasite, Perkinsus marinus a suspected causative agent for subtidal oyster mortalities experienced in the coastal waters of Georgia. Twelve growout bags (1 m x 0.5 m; 12.7 mm mesh), each containing 200 oysters, were placed in Jointer Creek, Georgia In March 1992. Bags (3 replicates each) were placed lntertidally and subtidally on the creek bottom and offbottom. Ten oysters per bag were removed monthly for twelve months beginning March 1992, and were inspected for prevalence and intensity of Perkinsus marinus, using the thioglycollate method. Oyster mortality and shell length data were
also evaluated. Neither prevalence (p = 0.3505) nor intensity levels (p = 0.2993) of Perkinsus marinus in oysters were significantly different among the treatments. Although there were no significant differences In prevalence or intensity of the pathogen among treatments, the intertidal offbottom treatment had the lowest values most frequently. Perkinsus marinus was present in all replicates every month. Prevalence and intensity of infection followed the typically observed pattern of maximum values in summer and fall and minimum levels in winter.
Subtidal bottom oysters experienced higher mortalities (p = 0.0022), but the prevalence and intensity of Perklnsus marinus in oysters were not significantly different between treatments. It appears therefore, that the oyster parasite, Perkinsus marinus is not the discerning factor in the higher mortalities witnessed in oysters placed subtidally on the bottom in the southeastern U.S. coastal waters.
Peer-reviewed.
1994-01-01T00:00:00Z