Projects

Oyster farming in Alabama: Identifying most viable practices

End Date: 2-1-12

Abstract

Despite the dramatic growth of oyster farming across the United States, in the Gulf of Mexico region, oysters are only farmed extensively, on bottom leases with the vast majority of production concentrated in Louisiana. Subject to environmental variability, the supply and quality of extensively farmed oysters varies widely. In contrast, oyster farmers using intensive, off-bottom methods focus on producing a steady supply of consistently premium oysters for the lucrative half shell niche market. A number of hurdles have hindered the growth of this industry within the region. As part of an expanding effort to overcome these hurdles for farmed oysters in Alabama and the region broadly, faculty at Auburn University are addressing the identification of possible niche markets, the potential for regional appellations as a marketing tool, and pre- or post-harvest treatments by the farmers to ensure food safety. In parallel with this effort, it is essential to provide beginning and prospective oyster farmers concrete, locally-derived quantitative production and economic data to address the where, what and how of oyster farming.

The goal of this proposed work is to quantitatively compare oyster aquaculture practices at coastal sites in Alabama to determine the most viable combination of methods, providing guidance to current and prospective oyster farmers in the North Central Gulf of Mexico region. Specifically, working with three current Alabama oyster lease holders, we propose to:

1) identify optimal sites for the nursery culture of hatchery-reared oyster seed along the Alabama coastline by deploying oyster seed at seven sites in the summer and fall of 2010 and 2011 to measure average daily growth and mortality rates,

2) compare the performance of native triploid (putatively sterile) oysters to half-sibling diploid oysters at the three lease sites planted in the fall and spring over 11-16 month grow-out periods to analyze differences in growth, survival, yield and condition index,

3) test and compare the effect of four different types of commercially available oyster culture equipment on oyster growth, survival and yield to market size (and the interaction of gear with ploidy) with oysters deployed in the fall and spring, and

4) determine the costs of production of the various combinations of production strategies tested here, and identify the least cost approach to intensive farming of oysters for each lease holder and prospective oyster farmers in the region.

This project relies on and promotes close collaboration with the industry participants and develops immediately applicable information (e.g., growth rates, mortality rates, costs of production, etc.) and hands-on experience. Additionally, the proposed project would create three working oyster farms along the Alabama coast, which can serve as demonstration sites for others in the region, supporting development of this industry broadly throughout the North Central Gulf of Mexico region.

Objectives

  1. To identify optimal sites for the nursery culture of hatchery-reared oyster seed along the Alabama coastline, based on statistical rankings of average daily growth and mortality of oyster seed.
  2. To compare the performance of native triploid oysters to half-sibling diploid oysters at the three lease sites in this study through the grow-out period, based on differences in growth, survival, yield and condition index.
  3. To test and compare the effect of four different types of commercially available oyster culture equipment on oyster growth, survival and yield through the grow-out period to market size.
  4. To provide site-specific oyster growth and survival data for each lease site.
  5. To characterize the ease of use and durability of four different types of commercially available oyster culture equipment used for production-scale farming of oysters.
  6. To determine the costs of production of the various combinations of production strategies tested here, and to identify the least cost approach to intensive farming of oysters for each lease holder.

Methodology

Year 1

  1. Conduct early spawning of half-sibling diploid and triploid Crassostrea virginica at the Auburn University Shellfish Laboratory, set on micro-cultch to produce ‘single’ oysters. Raise these in the hatchery and nursery to 12+ mm shell length prior to fall deployment at lease sites. Conduct a similar spawn in the early fall, for deployment in the spring of the second year.
  2. Test site-specific differences in juvenile oyster (seed) growth or survival among seven locations within Alabama’s coastal waters by deploying hatchery-raised oyster seed in a standard fashion for known, comparable periods of time at each site (~60 d) in both the summer and the fall, and measuring subsequent increases in size (shell length, shell width, shell weight, wet meat weight, dry meat weight, condition index, etc.) and mortality. Size and mortality data will be converted to average daily rates, and analyzed with ANOVA. Condition index will be calculated as a ratio of the dry meat weight to the cavity volume, multiplied by 100. 
  3. Continuously record and log hydrographic data at each of the three main lease sites with submerged data loggers, and periodically record hydrographic data at the remaining four sites with a handheld meter.
  4. Test site-specific differences in diploid and triploid oysters among the three lease sites, by deploying hatchery-reared half-sibling diploid and triploid oyster seed (sharing a common maternal parentage) in standardized, replicate oyster cages at each culture site in the fall of 2010 with subsequent sampling at 3 month intervals (again complemented by hydrographic data). Size, mortality and yield will be determined. These data will be analyzed with ANCOVA to account for any initial differences in seed size.
  5. Test the effect of four different commercially available oyster culture methods at one lease site, by raising hatchery-reared diploid and triploid oysters in a common garden experiment at the Sandy Bay lease site in a randomized complete block design stocked in fall 2010. Size, mortality and yield will be determined every three months, and data will be analyzed with ANOVA. Gear, Ploidy (diploid or triploid), and the Gear x Ploidy interaction will be tested.
  6. At the remaining two lease sites, compare oyster growth and survival in subsets of the different types of gear every 3 months after fall deployment.
  7. Track time spent by the oyster farmers for each type of gear, maintenance costs, and gear losses, and record qualitative comments about ease of use of each gear type.

Year 2

  1. Test site-specific differences in juvenile oyster (seed) growth or survival among seven locations within Alabama’s coastal waters by deploying hatchery-raised oyster seed in a standard fashion for known, comparable periods of time at each site (~60 d) in both the summer and the fall, and measuring subsequent increases in size (shell length, shell width, shell weight, wet meat weight, dry meat weight, condition index, etc.) and mortality. Size and mortality data will be converted to average daily rates, and analyzed with ANOVA. Condition index will be calculated as a ratio of the dry meat weight to the cavity volume, multiplied by 100.
  2. Continuously record and log hydrographic data at each of the three main lease sites with submerged data loggers, and periodically record hydrographic data at the remaining four sites with a handheld meter.
  3. Test site-specific differences in diploid and triploid oysters among the three lease sites, by deploying hatchery-reared half-sibling diploid and triploid oyster seed (sharing a common maternal parentage) in standardized, replicate oyster cages at each culture site in the spring of 2011 with subsequent sampling at 3 month intervals (again complemented by hydrographic data). Size, mortality and yield will be determined. These data will be analyzed with ANCOVA to account for any initial differences in seed size.
  4. Test the effect of four different commercially available oyster culture methods at one lease site, by raising hatchery-reared diploid and triploid oysters in a common garden experiment at the Sandy Bay lease site in a randomized complete block design stocked in spring 2011. Size, mortality and yield will be determined every three months, and data will be analyzed with ANOVA. Gear, Ploidy (diploid or triploid), and the Gear x Ploidy interaction will be tested.
  5. At the remaining two lease sites, compare oyster growth and survival in subsets of the different types of gear every 3 months after spring deployment.
  6. Track time spent by the oyster farmers for each type of gear, maintenance costs, and gear losses, and record qualitative comments about ease of use of each gear type.
  7. Develop full enterprise budgets that include operating (cash) expenses plus gear/equipment (fixed) costs to determine cost of production ($/oyster) for comparative use to determine the combination of factors that provide the least cost approach to raising oysters at Alabama coastal sites, based on treatment results (site, oyster variety, and culture method).

Rationale

For beginning and prospective oyster farmers along the Alabama coast, this study will provide basic but essential information on site suitability, oyster variety (triploid versus diploid) performance and culture methods. Comparison of developed budgets for each site, variety and method will provide a decision matrix of profitability for potential oyster producers, including current lease holders and oystermen. In concert with ongoing, complementary efforts (marketing, food safety), this work will support a viable domestic aquaculture industry with acceptable environmental impacts.

This project will produce peer-reviewed scientific publications, but will also focus on meaningful extension. We will publish user-friendly bulletins detailing the results and guiding prospective oyster farmers through the difficult start-up phase. We will also hold training workshops based on the results of this study, and interested individuals will be invited for guided site tours of the demonstration farms. Based on this, we expect to increase the general knowledge about oyster farming within the region, as well as extensively train individuals in oyster culture methods and techniques.

For More Information Contact: the MASGC Research Coordinator, Loretta Leist (Loretta.leist@usm.edu). 
Please reference the project number R/SP-23.