Adaptation and integration of remote setting, selective breeding and triploid production technologies to revitalize oyster culture in Delaware Bay

View the project final report

• 2011 annual report

Commodities

• Animals: shellfish

Practices

• Animal Production: general animal production
• Education and Training: extension, mentoring, on-farm/ranch research
• Sustainable Communities: local and regional food systems

Oyster production in Delaware Bay and elsewhere is a fraction of historic levels. Formerly prosperous communities have been decimated as boat works, marinas, shucking houses, and other oyster-associated industries have closed. Rural communities located in the impoverished counties of Cumberland and Salem New Jersey have lost an important source of jobs and income. This project will combine intensive hatchery culture methods with extensive grow out methods to revive production on 33,000 acres of leased oyster grounds in lower Delaware Bay, stimulating local communities. Specifically, we will combine advances in shellfish husbandry (hatchery production, remote setting), selective breeding (fast growth, disease resistance), and chromosome set manipulation (triploidy), for use in traditional extensive aquaculture operations to support the shucked oyster market. Application of these technologies has been limited to intensive aquaculture and the production of shell stock oysters for the half shell market leaving a void in supply to meet demand for shucked oysters. This demand is currently inadequately addressed by harvests from ailing oyster fisheries resulting in an increased reliance on imports from foreign markets. We will test whether or not hatchery produced triploid larvae from selectively bred oyster lines can be remotely set on shell and economically grown on bottom to market size. A key objective is to get enough oysters to survive their first year of cultivation where predation typically imposes considerable mortality. By planting hatchery produced oysters before predators are active and by using fast growing, selectively bred triploid oysters, we believe we can overcome this problem.

Task 1 – Presample and prepare grounds. In April 2011, Harbor House will sample lease 20 acres. Five acres will be set aside for each treatment: spatted shell planted on the bottom, shell planted on the bottom, and an unplanted control area. Each 5 acre plot will amount of existing shell and oysters on each plot. Samples will be processed using standard protocols Rutgers University has developed for their annual Delaware Bay Oyster Seed Bed Stock Assessment (HSRL 2010). Briefly, equal subsamples from three random tows are combined to create a composite bushel that is then sorted to quantify the amount of live oysters, dead oysters (articulated oyster shells), cultch (disarticulated oyster shells), and debris. As needed oysters will be removed or redistributed within each lease such that each plot begins with approximately equal densities of oysters. One plot will then be left alone as a control. Another plot will be planted immediately with a layer of shell upon which the hatchery produced spatted shell will be planted. The remaining plot will be planted with clean shell in early July to receive natural recruitment.

Task 2. Produce triploid, disease-resistant larvae and remotely set on cultch. Rutgers MADF will produce larvae using their disease resistant lines. Harbor House Seafood will purchase these larvae and set them remotely in tanks at their facility in Port Norris, NJ with Rutgers training and supervision. Setting tanks will be well aerated to ensure survival and circulation of larvae before and after setting. Larvae will be provided 48 hours to set and metamorphose before being transferred to a flow through system using water from the adjacent Maurice River until they are ready for deployment on the bottom area. Spat setting success will be determined at this time.

Task 3. Deploy spatted shell. As soon as possible in late May or early June, spatted shell will be deployed. Spatted shell will be loaded onto the vessel Shell Game II and deployed on bottom.

Task 4. Shell planting. Oysters begin to spawn in Delaware Bay when water temperatures exceed 76oF. Standard practice is to plant shell at the end of June or in early July; shell will be planted between the last week of June and the second week of July using the industry standard. This planted shell will be monitored for set and subsequently for growth and mortality as a comparison with the spat on shell.

Task 5. Monitor growth & survival. Samples will be collected by oyster dredge at monthly intervals from each treatment to measure growth and mortality following well-established protocols (Bushek 2010, HSRL 2010). GPS positions will be recorded at 10 second intervals to produce a track of known distance for each tow. Bottom water temperature and salinity will be recorded for each sample. The total volume of each tow will be recorded and a composite bushel consisting of randomly collected oysters and boxes from the three replicate dredge hauls (approximately one third of a bushel from each haul) will be created and then sorted to enumerate gapers (= dead oysters with meat remaining in the valves), boxes (= hinged oyster valves without any meat remaining) and live oysters. Boxes will be further categorized as new (= no indication of fouling little sedimentation inside valves) or old (= heavily fouled and or containing extensive sediments) to provide an indication of recent mortality. Boxes will be returned to the laboratory for closer inspection to identify the proportion dying from oyster drills or crab predation identified by the presence of drill holes or chipping of the oyster bill. The volume of live oysters, boxes and remaining material will be measured. The counts of oysters and boxes are used to estimate mortality as described by Ford et al. (2006), whereas the proportionate volumes and total volume of the haul are combined with tow length data and dredge size to calculate a density of oysters on the bottom. These two measures, monthly percent mortality and density of oysters on the bottom, provide independent estimates of mortality. Up to one hundred randomly selected oysters from this bushel will be returned to the laboratory where shell heights (hinge to bill) can be accurately measured to determine size frequency in the population. Recent boxes will be returned as well to identify the size frequency of oysters dying each month. Care will be taken to avoid any bias in sampling oysters by systematically working through the sample until 100 oysters are identified. If over set occurs on spatted shell, a separate sample of 100 spat comprising over set will be collected and measured as well. It is understood that the sampling gear will bias the collection toward larger animals as dredge efficiency studies have shown (Powell et al 2007), but such bias is presumed constant across sampling dates.

Task 6. Analyze results. Results will be analyzed using standard statistical procedures for comparing growth, survival and mortality. Namely, regression analyses, survivorship analyses, ANOVA and von Bertalanfy growth curves. The ultimate response measures, however, will be the abundance and size the spatted cultch, then planted shell and finally the control plots.