WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2025 47 (CONTINUED ON PAGE 48) Beyond water purification, oysters are also exceptional ecosystem engineers. By forming extensive reef structures in shallow coastal and estuarine waters, they create essential habitat for numerous marine species, including fish, crabs, and invertebrates (AKRF, 2023). These biogenic reefs provide shelter, breeding grounds, and foraging areas, effectively supporting biodiversity and increasing the productivity and resilience of marine ecosystems (Museum of the Earth, n.d.). In addition to promoting biodiversity, oyster reefs act as natural barriers against coastal erosion. By absorbing and dissipating wave energy, they protect shorelines from the impacts of storms, rising sea levels, and increasingly frequent extreme weather events such as hurricanes and tsunamis (Pew Charitable Trusts 2020). The complex, three-dimensional structures of these reefs further enrich the marine environment. Lastly, oysters play a central role in nutrient cycling. Their waste products support detritivores like worms and amphipods, which in turn form the base of the marine food web. This interaction sustains a wide range of marine species and enhances habitat complexity in estuarine and coastal environments. Despite their unassuming appearance, oysters have a profound ecological impact. As such, protecting and restoring oyster populations is critical to preserving the health, balance, and resilience of marine ecosystems. From Shore to Table: The Hands that Harvest Pamarawan Island, located in Malolos, Bulacan, within the northern part of Central Luzon, Philippines, is one of the last remaining fishing communities in the region. Known for its abundant supply of fish, crabs, and shrimp, the island also serves as a major oyster-producing community (Foronda 2018). The farming process begins with the cleaning and preparation of empty oyster shells. It is essential to remove any excess debris, such as moss, to ensure a clean surface that facilitates the settlement of oyster spat. The cleaned shells are then sun-dried to create an environment conducive to larval attachment. Women, including farmers’ wives, play a significant role in this critical step of the process. Subsequently, oyster farmers make holes in the shells, typically using a hammer and nail. This is necessary for attaching the shells to nylon ropes (Figure 2), which will function as supports within bamboo structures. These bamboo setups are designed to suspend the ropes (Figure 3), along with the oyster shells, fully immersed in saltwater, thereby optimizing conditions for oyster growth and development. To ensure successful reproduction, mature oysters are either maintained in bamboo stands or sea sediments during the planting season. During this period, farmers anticipate the arrival of the so-called Kapitan the male gametes from mature oysters (laon na talaba) which fertilize the eggs released by female oysters through broadcast spawning. The release of gametes in oyster farming is strongly influenced by a variety of environmental cues, including temperature, tidal patterns, and chemical signals in the water. Temperature is particularly significant in regulating spawning activity, which typically occurs when water temperatures exceed 14°C, with peak spawning activity occurring around 19°C (Cano et al. 1997, Enriquez-Diaz et al. 2009). Differences in temperature across habitats, such as the Baie des Veys and Marennes-Oléron, have been shown to significantly impact the timing and intensity of gametogenesis (Enriquez-Diaz et al. 2009). In addition to temperature, tidal patterns are closely linked to spawning events, particularly during high tides of perigean spring tides. The onset of spawning typically coincides with water current peaks, suggesting that hydrodynamic conditions are also critical in triggering gamete release (Bernard et al. 2016b). Chemical cues in the water have been found to influence larval oyster settlement behavior. The presence of ammonia, especially in adult-conditioned seawater, correlates with increased settlement rates in older larvae, highlighting the importance of chemical signals in the reproductive cycle (Fitt and Coon 1992). While these environmental factors are crucial for spawning, local variations in conditions such FIGURE 2. Oyster farmers examining oysters prepared for harvest. In the background, the stakes used to suspend oyster lines or clusters during the growout period are clearly visible. Photo credit: Kathleen Ybanez. FIGURE 3. A cluster of oysters suspended on a single nylon line, exhibiting a natural grouping behavior. Mussels are also observed cohabiting the substrate, suggesting a potential symbiotic or commensal interaction. Photo credit: Michael Candelaria.
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