Progress 09/01/09 to 02/28/13
Outputs
OUTPUTS: URI Effects of hypoxia on the performance and susceptibility of juvenile New England Hybrid oysters to Roseovarius crassostreae Jessica Peisz, M. Rice, M. Gomez-Chiarri & R. Rheault. The purpose of this study was to elucidate the effect of low oxygen levels on the growth, survival, and susceptibility of juvenile diploid and triploid New England Hybrid oysters to Roseovarius crassostreae. Diel-cycling hypoxia was reproduced in the laboratory using a computer operated dissolved oxygen system. Oysters were exposed to hypoxic conditions (5 and 20% saturation) for 13 hours during the evening. Shell height and width, oyster weight, and mortality were measured once a week for 4 weeks. After 4 weeks, oysters were challenged with R. crassostreae (1x10⁶ cells/ml) and mortalities were measured every 48h for 2 weeks. RWU What is the relationship between bivalve size at the time of planting and the survival from predation and/or other environmental conditions Small (2-3mm) shellfish (quahogs and oysters) seed were purchased in June from a commercial hatchery.As the seed approached the target size, a subsample was tested for disease conditions to ensure they were eligible for movement from the bay into the pond. We proposed to deploy seed into the experimental plots at the following valve size stages: Oysters = 8mm, 25mm, and 40mm (or the maximum size achieved during the nursery season); Quahogs = 6mm, 14mm, and 22mm (or the maximum size achieved during the nursery season). Planting density during the Objective 1 experiment was 125 ind/m2 for oysters and 250 ind/m2 for quahogs. What is the optimal density for planting Small (2-3mm) shellfish (quahogs and oysters) seed were purchased in June from a commercial hatchery and were reared in a conventional shellfish nursery. The size range planted under Objective 2 was to be derived from the optimal planting size determined during Objective 1 of this study (initially we proposed to conduct these experiments independently in Years 1 and 2; however, this was not followed due to delays in starting the project.) The layout of the experimental plots for Objective 2 was adjacent to the plots utilized for Objective 1. We proposed to deploy seed into the experimental plots at the following planting densities: Oysters 25 ind/m2, 125 ind/m2, and 250 ind/m2; Quahogs 25 ind/m2, 250 ind/m2, and 500 ind/m2. Upon completion of the data analysis, this information will be distributed to regional shellfish farmers through a variety of mechanisms. The primary individuals involved in the information transfer are the PI(Leavitt) and his Field Technician(M. Griffin). This information is planned for formal and informal presentations to local and regional shellfish farmers. The venues would include state aquaculture association meetings, and professional meetings, including the Northeast Aquaculture Conference and Exposition and the Milford Aquaculture Seminar. We have begun to prepare the information generated by this project as a technical bulletin/for general consumption that will be posted on internet websites, e.g. the NRAC Regional Aquaculture Extension Project, and distributed on internet listserves. PARTICIPANTS: The principal investigators are either members of the shellfish management community or members of the shellfish research community. TARGET AUDIENCES: Shellfish aquaculture industry PROJECT MODIFICATIONS: The locations were changed for the second year of the oyster and quahog density and size study because of adverse environmental conditions. The new locations were not affected by severe weather and the research was completed.
Impacts
URI Results suggest that diploid oysters perform better than triploids at 5% DO saturation. Overall, mortality was higher for triploids than diploids at all three oxygen saturation levels. R. crassostreae challenge results showed there was less mortality of diploid oysters exposed to 100 and 20% saturation than 5% saturation (p=<0.001). Conversely, triploid challenged oysters experienced less mortality at 100 and 5% saturation than 20% saturation (p=<0.001). We see an effect of hypoxia on the growth and mortality of the oysters. Shell height was significantly greater after 4 weeks at 100% saturation than at 5 and 20% DO saturation levels for both triploid and diploid oysters (p=<0.001). We observed a similar effect of treatment on shell width with significantly less growth in hypoxic treatments compared to controls (p=0.001). Control oysters grew significantly larger than oysters exposed to 5 and 20% DO saturation. These results suggest that diploids may be able to tolerate hypoxia better than triploids at 20% DO saturation. RWU Results: Quahogs and oysters were planted according to size and density criteria in all four experimental sites in November 2010. We experienced a severe wind event out of the northwest and the oysters and quahogs were dramatically scattered about the general area of the sites completely disrupting the controlled plantings of the size related and the density related experiments. It was decided to abandon the experiment for 2010 and to locate new sites. 2011: The experimental sites were changed to protect the shallow sites from disruption by winter storms. Two sites were selected, one in Narragansett Bay and a second in Point Judith Pond. The Narragansett Bay site was located in Bissel Cove in the vicinity of a shellfish restoration site and a shellfish farming region in the Bay. Bissel Cove is a shallow site where the sediment structure varies between hard sand and soft mud. The coastal pond site was located on a commercial oyster grower's site, on the back side of Ram Island in Point Judith Pond and had both hard and soft substrates. Deployments to address both objectives were established at both sites. Although final data analyses have not been completed, some general results can be relayed. The density control tracers (marble fragments planted at 125 pieces/m2) collected at all sites demonstrates that the planting protocol was variable but within the targeted range. Growth of both shellfish species was substantial. Size at planting for both species had a profound effect on survival although little impact on growth rate. Both oysters and quahogs demonstrated a survival gradient where those animals planted at a greater size had a higher chance of survival. Density of planting seemed to have lesser consequences than size at planting. Both oysters and quahogs realized a higher rate of survival at the medium planting density than at either extreme. The role that substrate type plays in planting strategy for the shellfish farmer may be important. The information suggests that substrate type influences growth rate and may be important in terms of survival of planted seed relative to planting size and/or planting density.
Publications
- No publications reported this period
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: The contractual projects with Roger Williams University (RWU)and the University of Rhode Island (URI)each began in September 2010. The URI hypoxia project is in the construction phase with the necessary pumps, raceways, oxygen strippers etc. being assembled. The research aspect will be conducted in the winter 2011. The RWU project received the research permits for the field studies in September 2010 and work began immediately. Initial results will be determined in spring 2011. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The research phases are currently underway with results to be determined in 2011.
Publications
- No publications reported this period
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