Shellfish Basket Study at Zuniga Shoals

The San Diego Unified Port District proposes to perform baseline testing of the health and quality of adult oysters, mussels, and seaweed at one location in Zuniga Shoals using shellfish baskets and conducting concurrent water quality monitoring at this location. The Project is anticipated to occur over the course of two months in the fall or winter of 2025–2026. The San Diego Unified Port District (Applicant or Port) proposes to perform baseline testing of the health and quality of adult oysters, mussels, and seaweed at one location in Zuniga Shoals (Figure 1) using shellfish baskets and conducting concurrent water quality monitoring at this location (the shellfish and seaweed health testing and water quality testing are collectively referred to as the “Project”). The Project is anticipated to occur over the course of two months in the fall or winter of 2025–2026 and would include (1) species harvesting and depuration, (2) the installation of a buoy system (see Figure 2), which would include eight shellfish baskets containing shellfish and seaweed species, and (3) sampling of the shellfish and seaweed, and water quality monitoring. The purpose of the Project is to assess the potential for deployed shellfish to be used to promote denitrification and water quality filtration through shellfish and seaweed co-culture experiments at the proposed study location with denitrification capacity assessments. The results of the Project would provide data on the denitrification capacity of shellfish and seaweed. Findings could be used in conjunction with previous shellfish basket study and water quality monitoring findings to inform the potential for future shellfish and seaweed aquaculture siting, as well as the use of shellfish and/or seaweed for potential restoration activities and bioremediation projects. The Project would study two species of shellfish and one species of seaweed: adult Pacific oysters (Crassostrea gigas) and adult Bay mussels (Mytilus galloprovincialis/M. trossulus) and green seaweed (Ulva lactuca). As described below, all shellfish and seaweed used in the Project would be harvested from existing shellfish and seaweed populations in San Diego Bay (Bay). Shellfish and seaweed would be harvested by hand from existing structures within the Bay. Then, the harvested organisms would undergo depuration at the Coastal and Marine Institute Laboratory at San Diego State University to eliminate the sampling bias associated with the existing Bay water quality conditions. This depuration would occur seven days before deployment. After harvesting and depuration, the shellfish and seaweed species would be placed into eight (8) shellfish baskets for deployment. Following depuration, the buoy system would be installed at the Project location. No eelgrass resources are known to occur within the project footprint. Please see Figure 2 for the configuration of the proposed buoy system. This would include: • One 600-pound 2 foot by 2 foot by 2-foot concrete block and up to three additional concrete weights in five-gallon buckets that are up to 100 pounds each and would be placed on the seafloor • One 5/8" nylon line approximately 20 feet in length, which would connect the concrete block to a surface buoy • One 5/8" nylon line approximately 15 feet in length (tether line), which would be connected to an additional surface buoy and connected to the longer nylon line with a 3/8" shackle • Eight shellfish baskets, approximately 25 inches by 10 inches by 6 inches in size, which would be secured to the tether nylon line via secure clips on the baskets, and • At least one additional submerged standard rubber marine-grade buoy, to ensure the baskets remain at a depth compatible with sampling, if necessary In total, the buoy system would have an approximate total radius of up to 30 feet and a bottom radius of three to four feet distributed between the concrete block and additional weights. A maximum of two people would be required to deploy, and later remove, the buoy system (Figure 2) at the proposed location (Figure 1). Following completion of the study, Port staff would remove all baskets from the water. Port divers would approach the site again, evaluate conditions at the surface and at bottom depth, bring the buoy onboard and retrieve the weights by chain/cable onto the vessel. Port staff will provide notification to Coastal staff when the baskets are deployed and removed. The eight baskets would be filled with the shellfish and/or seaweed species as follows: • One basket would contain between 80–150 adult Pacific oysters at a high stocking density • One basket would contain between 80–150 adult Bay mussels at a high stocking density • One basket would contain between 40–80 adult Pacific oysters at a low stocking density • One basket would contain between 40–80 adult Bay mussels at a low stocking density • One basket would contain between 40–80 adult Pacific oysters at a low stocking density and 3 pounds of green seaweed • One basket would contain between 40–80 adult Bay mussels at a low stocking density and 3 pounds of green seaweed • One basket would contain between 80–150 adult Pacific oysters at a high stocking density and 3 pounds of green seaweed • One basket would contain between 80–150 adult Bay mussels at a high stocking density and 3 pounds of green seaweed The buoy system would be deployed over a total estimated time of 60 days, or two-month period. It is anticipated that the shellfish baskets would be installed about a week after the buoy system is deployed, and that the shellfish baskets would be removed about a week prior to removal of the buoy system. Shellfish tissue, seaweed samples, and water samples would be collected frequently, anticipated to be on a weekly basis, during the deployment of the shellfish baskets. The deployment period of the shellfish baskets would allow adequate time for the shellfish to filter water and accumulate nutrients present in the surrounding waters. Taking multiple samples would be necessary because it would allow the Applicant to assess how water quality, shellfish tissues, and seaweed samples change over time with the presence of shellfish and seaweed during the deployment period, and additional sampling may be needed during the deployment period. The Applicant would send the collected samples to an off-Tidelands location (University of North Carolina at Chapel Hill and Weck Laboratories) for analysis. On the final day of deployment, all equipment, including any remaining shellfish and seaweed, would be removed from the water. Removal of the buoy system from the proposed location would require approximately one day to complete. The Project location would be accessed by small boat for basket installation, sampling, and removal. To conduct this study, the following would apply to the Applicant to manage and reduce marine debris: Marine Debris Reduction and Management. Port staff and/or consultants shall carry out the operation consistent with the following marine debris reduction and management practices. A. Storm Damage and Debris. As soon as safely and reasonably possible following storm or severe wind or weather events, Port staff and/or consultants shall patrol each study location for escaped or damaged equipment. All equipment that cannot be repaired and placed back into service shall be properly recycled or disposed of at an appropriate onshore facility. In addition, Port staff and/or consultants shall retrieve or repair any escaped or damaged equipment that it encounters while conducting routine sampling and/or maintenance activities associated with the pilot Project. If the escaped gear cannot be repaired and replaced, it shall be properly recycled or disposed of on land. B. Gear Marking and Replacement. Port staff and/or consultants shall mark all shellfish baskets and floats in an easily identifiable manner with identification information. Markings shall be securely attached and robust enough to remain attached and legible after an extended period in the marine environment (e.g., heat transfer, hot stamp, etching, etc.). Basting floats currently in use shall be marked or replaced with marked versions when replanted and all unmarked gear shall be replaced. In this way, in the event that gear or equipment becomes displaced or dislodged from the experiment, it shall be the Port’s responsibility to retrieve the material from the shoreline, open water, eelgrass beds, mudflat, or submerged bottom with minimal damage to the resources affected. Once located, such material shall be removed as soon as feasible and properly disposed of, recycled, or returned to use. C. Ongoing Operations. Port staff and/or consultants shall not leave or temporarily store tools, loose gear, or construction materials on its leased tidelands or surrounding areas. All study equipment installed on and in use at the study sites shall be kept neat and secure and maintained in functional condition. Port staff and/or consultants shall carry out regular bed inspections and maintenance activities to help ensure that broken, collapsed, fallen, or buried gear is fixed or removed in a timely manner. D. Bed Cleaning at Harvest. Port staff and/or consultants shall carry out a thorough inspection to locate and remove loose, abandoned, or out-of-use equipment, tools, and accumulations of oysters from the surrounding substrate. Oyster shell shall not be intentionally placed or deposited within the lease outside of cultivation gear, and oysters or oyster shell accidentally spilled during the experiment shall be immediately collected and removed. E. Excessive Gear Loss or Maintenance Failures. If the Port is found to be responsible for consistently extensive loss of equipment into the marine environment or is consistently failing to maintain its equipment in an intact and serviceable condition, Port staff and/or consultants shall modify its equipment and/or operations to minimize equipment loss and mitigate impacts to affected habitat. Due to its nature and limited scope, construction of the Project would generate a minor amount of vehicle trips and would require limited use of equipment. Therefore, impacts related to air quality, greenhouse gas emissions, and transportation and traffic are not anticipated to occur. Furthermore, the Applicant would be responsible for complying with all applicable federal, state, and local laws regarding construction demolition debris, hazards and hazardous materials, and stormwater, as well as acquiring necessary permits from relevant resource agencies, such as the California Coastal Commission, Army Corps of Engineers, and Regional Water Quality Control Board, including the necessary real estate or access agreements, or coastal development permitting for the proposed Project site, which is not within the District’s permitting or coastal jurisdiction.