WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2024 39 growers. They deploy oyster seed across their lease areas with only a general idea of where it will end up on the seafloor. This approach makes it difficult for them to locate the ready-to-harvest oysters later. Also, for oyster spat or seed to thrive and become adult oysters, it is crucial that the seed land on a hard bottom substrate instead of a soft bottom like sand, mud, or silt. The likelihood that seed will die due to suffocation if deployed over a soft bottom is much higher. Due to the inexact practices that contribute to seed mortality, seed requirements are higher, leading to increased costs for farmers. Additionally, seed availability is limited in the Chesapeake Bay region, making it more important to be efficient with seeding practices. Oysters are sessile and form clusters, therefore, as the oysters grow, they need to separate to ensure they develop the best shape and size for market choice. However, if left attached to each other, they cannot develop in a desirable quality, shape, and size. Therefore, growers may use bagless dredging methods during growth to break up clumps of oysters. Unfortunately, this process is inefficient and costly. Growers lack precise information regarding the location and size of the clusters. As a result, they resort to random dredging across the lease area. This random approach consumes significant time and fuel, and can also kill small oysters as the clumps are broken up. Figure 2 shows the dredge that is commonly used to harvest oysters from the seafloor. The frequency, time, and costs associated with dredging for harvest could be significantly reduced if growers had advanced knowledge of where harvestable oysters are located. However, without technological intervention, this seems impossible, as the human eye cannot penetrate through the murky water. This inefficiency not only adds to operational costs but may also result in increased environmental impacts. Random dredging is not only costly in terms of input requirements, including labor and fuel, but On-bottom oyster culture, also known as spat-on-shell bottom culture, is a traditional shellfish farming practice prevalent in the Chesapeake Bay, where growers obtain Submerged Land Leases (SLL) from their respective states. The Chesapeake Bay region (Figure 1) offers ample acreage with suitable depth and food availability for bivalve filter feeders to thrive. In their natural setting, oysters spawn and produce eggs that result in larvae which then attach themselves to substrate such as oyster shells or rocks and grow into adult oysters. However, in Maryland most bottom culture of oysters is accomplished using remotely set spat. The method gained traction in response to the significant decline of the wild oyster population in the Chesapeake Bay region. This decline was attributed to various factors, including disease, habitat loss, overharvesting and poor water quality. A 2011 study by the University of Maryland Center for Environmental Science, published in Maryland Sea Grant (2023), highlighted the severity of the situation, indicating that only 0.3 percent of the population remained from its levels in the early 1800s. To restore the oyster population in the Chesapeake Bay region for both ecological and economic purposes, oyster aquaculture has become the primary approach. Once oysters are deployed on submerged lease areas, they grow by feeding on phytoplankton through their filter feeding mechanism. Growing oysters on the sea bottom provides a lower-cost production method as compared to off-bottom culture. However, there are still challenges affecting the efficiency of on-bottom oyster production in modern times. That inefficiency results from seed mortality, excess fuel use, and labor requirements, all of which could be minimized with the implementation of new methods and technological advances. Current Challenges in On-bottom Oyster Production Current oyster aquaculture heavily relies on guesswork by Is Technological Intervention Feasible for the U.S. Shellfish Aquaculture Industry? A Case Study from Maryland Oyster Farms Renu Ojha, Jonathan van Senten and Allen Pattillo FIGURE 1. Chesapeake Bay. It spans over 64,000 square miles and is a highly productive estuary in the United States. It’s fed by over 150 rivers and streams, making it a vital ecosystem. Please check the https://dnr.geodata.md.gov/Aquaculture/ to see the location of active oyster leases in Chesapeake Bay. (CONTINUED ON PAGE 40)
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