Theses and Dissertations


Title: An Oyster gardening program and analysis of two off-bottom Oyster culture systems and enteric microorganisms in Mobile Bay, Alabama

Name: Hamilton, Kimberly

Degree: MS

Chair: D. LaDon Swann

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2002

Pages: 138

Keywords: Oyster gardening program,off-bottom Oyster culture systems,enteric microorganisms

Abstract:

Restoration programs for the eastern oyster, Crassostea virginica, in Mobile Bay, Alabama are used to increase the number of oysters on new or existing reefs and to improve ecological functions such as providing habitat and water filtration. To educate the general public of the importance of oyster ecology and to provide oysters for restoration, an oyster gardening program was developed. The volunteer program was implemented in Mobile and Baldwin counties, Alabama, along Mobile Bay and Mississippi Sound and monitored for six months beginning in May, 2001. A total of 30 volunteers representing sites located in conditionally approved oyster harvesting waters were provided a Taylor float (surface area of 0.74 m2) for growout of oysters. Taylor floats for the first group of 15 volunteers (phase 1) were stocked on May 13 and 14 with 1,000 hatchery-reared oyster spat with an average height of 36.2 mm (range: 5.0 to 81.0 mm), and Taylor floats for the next group of 15 volunteers (phase 2) were each stocked from July 2 to August 9 with 200 shells with wild-caught spat with an average height of 12.5 mm (range: 4.0 to 40.0 mm). Growth and condition of oysters and water quality parameters of the 30 sites were grouped and compared between six geographic locations. All 30 sites were successful in growing oysters for restoration. Oysters grew greater in height in Mobile County, especially on Dauphin Island, Point aux Pines, and Dauphin Island Parkway, than Baldwin County. However, the condition index of oysters was greater in Baldwin County than in Mobile County. Three sample sites on the north side of Dauphin Island, Alabama, were used to compare the growth (height) of oysters at different stocking densities of the same size cultchless spat (average: 40.1 mm, range: 22.0 to 59.0 mm) between two different types of floats, Taylor (surface area of 0.74 m2) and Eastfields (surface area of 0.35 m2). Three treatments of 1,014, 676, and 338 oysters/m2, with three replicates per treatment, were stocked into each Taylor and Eastfields float. Growth and survival of oysters in each float type were compared and correlated with water quality parameters (temperature, dissolved oxygen, and salinity). Oysters in the Eastfields floats demonstrated greater total growth at all densities than oysters in Taylor floats. Average daily growth rate of oysters was greater in Eastfields floats at lowest densities compared to Taylor floats. Survival of oysters was similar in each float type. Average survival of oysters between the three treatments and two float types ranged from 30.1% to 56.4%. From June 21, 2001 to March 2, 2002, water temperatures ranged from 8.5°C to 29.7oC, salinity ranged from 10.6 ppt to 29.0 ppt, and dissolved oxygen ranged from 5.2 mg/L to 10.3 mg/L. The Eastfields floats required more labor for fouling control and were less durable than Taylor floats. f fecal coliforms. There was no relationship between fecal coliforms and E. coli in the oysters compared to fecal coliforms and E.coli in the water. However, there was a significant positive relationship between fecal coliforms in oysters and E. coli in oysters. There was a significant, but very weak, positive relationship between (1) fecal coliforms in oysters and water temperature and (2) rainfall and fecal coliforms in the water. The male-specific bacteriophage levels were consistently lower than the level of detection, indicating that municipal wastewater was not a likely cause of fecal coliforms. We speculate that a high number of birds and their droppings adversely affected the sanitary quality of oysters and water at each site. These findings were used to educate volunteers about enteric microorganisms and may have implications for future site selection of the oyster gardening program.

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