Biofouling is a costly and serious problem for all types of aquaculture and with certain types of shellfish, culture is highly vulnerable. Fouling organisms not only clog gear, stopping water flow and food delivery, they can also settle and grow on the cultured organisms themselves, causing reduced growth rates, decreased product quality and mortality. In response to increasing problems with biofouling on our oyster and mussel aquaculture farm, this Phase I proposal seeks to 1) determine quantitatively biofouling on mussels, oysters and their associated gear at two commercial aquaculture sites in Maine; 2) characterize and quantify the biofouling effects on the growth and mortality of oysters and mussels and their associated gear; 3) assess and prioritize the relative importance of each fouling species to the overall fouling problem to determine which species will be targeted for mitigation studies in Phase II and 4) make a preliminary assessment of one novel and promising biofouling mitigation technique. These studies will identify and characterize fouling organisms and communities on cages/ropes/rafts/bottom (mussels and oysters) at two aquaculture farms in Maine. It is our intention in Phase II to test and screen potential means of mitigation and control for the dominant species identified in Phase I. OBJECTIVES: 1) Determine quantitatively biofouling on mussels, oysters and their associated gear at two commercial aquaculture sites in Maine. 2) Characterize and quantify the biofouling effects on the growth and mortality of oysters and mussels and their associated gear. 3) Assess and prioritize the relative importance of each fouling species to the overall fouling problem to determine which species will be targeted for mitigation studies in Phase II. 4) Test at least one means of possible mitigation (to be determined after assessment of current summer studies of Whitlatch) at the farm scale. Given the time frame and funding level of Phase I, these tests can only be preliminary, but will provide the basis for development of Phase II research. APPROACH: Objective 1 We will deploy racks with PVC and limestone settlement panels beginning in May, 2007. We will assess three separate plots for each aquaculture technique on both the oyster and mussel farm sites. All sites will be sampled simultaneously. At each site we will deploy racks with four settlement panels and sample them every two weeks through October to assess fouling species. Racks will be placed as close to the shellfish as possible (within 0.25 m). After exposure, we will recover the panels and identify all newly settled fouling organisms. The panels will also be photographed with a high resolution digital camera. Fouled panels will be replaced with clean panels after each sampling to capture newly settling species. We will compare differences in fouling organisms present throughout the season among sites using ANOVAs. Objective 2 A. Effects of fouling of three ascidians on growth and mortality of shellfish spat 10-20 mm cultchless oyster spat will be obtained from the hatchery and cemented to marked oyster shells using underwater epoxy. All shells will then be photographed and analyzed to measure initial sizes of the spat. 20 shells with attached spat will then be placed in small mesh bags (treated as replicates for the experiment). Both sets of experimental units (shell bags or ropes) will be randomly assigned to control or ascidian treatments. To insure the recruitment of ascidians, all of the ascidian treatment experimental units will be exposed to competent larvae of either Didemnum, Ciona, or Steyla in the Darling Marine Center laboratory. Five control and 5 ascidian-treatment experimental units of each type (shell bags and ropes) will be exposed at two commercial farm sites. B. Effects of fouling of three ascidians on growth and mortality of adult shellfish As in the spat experiments, separate experiments will be conducted with each of the 3 fouling species. In each experiment 5 replicate control and 5 replicate ascidian treatment experimental units of each type will be exposed at each of two sites. Experimental units will be suspended from surface floats 1 m below the water surface and will be collected and examined after 1, 3, and 6 mos. All replicates will be photographed and the extent of fouling by the ascidians and other species quantified. Objective 3 Relative percent cover for the dominant species from the experiments in Objective 1 will be used as an assessment tool. Panels will also be photographed and fouling organisms weighed by species. Growth and mortality of the oysters or mussels will be used as the principal determinants making this assessment for the three species examined in Obj. 2. Objective 4 Although we will not have any definitive information to support the optimal means of mitigating biofouling until Phase I studies are complete, we are anxious to conduct preliminary studies on promising methods. Ongoing studies by one of the consultants (Whitlatch) may shed some light on one approach by fall, 2006. We suspect that water turbulence may be used to reduce fouling action and will design a suitable commercial scale experiment to test this hypothesis
