Moreover, they translocate spat collectors from one grow-out site to another several times, since the optimal oyster seed density varies by destination region. Miyagi producers’ practices of harvesting seed oysters therefore rely on improvisation in the face of unpredictability, as they describe their daily work as “ shiodoki-shigoto,” which means that it hinges on day-to-day tidal modality. As such, they describe spat collection in the wild as “gambling,” because their most confident predictions are based on daily climatological data and observations can often go awry. According to their rule of thumb, spat collection is more likely to be successful when the number of barnacle larvae in water samples becomes equal to that of oyster larvae. Based on these shared data and their own daily inspection at sea, each farmer determines the right timing to suspend collectors to attract oyster larvae. In early July, local farmers begin collecting samples of swimming oyster larvae in cylindrical-conical plankton nets and measuring changes in water temperature, salinity, and the size of larvae under the microscope, on a rotating basis. Before microscopic investigation became established, trumpet vine bloom used to be an indicator of the timing of oyster spawning. Spawning of Pacific oysters depends on a rise in water temperature above 18☌. If the oyster farmers suspend them too early, the surface of the scallop shells becomes covered with barnacles and seaweed consequently, spat collection would be unsuccessful. Given the varied trajectories of these environmental disturbances to marine resources, how is the collection of natural oyster spat ( ten’nen saibyo) carried out? In Higashi-Matsushima, spat collection in the wild requires skilled knowledge: putting strings of flat scallop shells in the water for larvae, so that the oyster has the opportunity to settle on at the right time. Their biological immobility, therefore, serves as a fixed-point indicator, helping in the understanding of changes in the local marine ecosystem. Unlike other “free-living” bivalves, such as scallops, which are capable of swimming some distance across the sea bed after being released, mature oysters can neither move to find optimum living conditions, nor escape from predators. Multispecies parasitic and symbiotic relationships form affective experiences. Both of these sessile organisms were considered a nuisance since they hindered oysters’ growth. According to one of the local producers, the kinds of species that attach themselves to oysters have changed. While participating in a harvest, I saw a conspicuously orange spongy creature and Mediterranean mussels ( shiuri-gai) clinging to two-year-old Pacific oysters. As the ebbing tide widened the estuary-which had an impact not only on the salinity of brackish water but also on the entire marine and estuarine ecosystem-deformation caused a change in the circulation of phytoplankton and other such nutrients. It is also notable that unruly multispecies entanglements emerge as a result. In addition, they started installing buoys equipped with real-time remote sensors to collect data on the weather and the ocean, including wind, current, tide, and wave intensity at various depths, all of which are used to ensure a controlled environment for oyster production. Since the earthquake, local farmers have been more rigorously attentive to placing their oyster rafts in the right spots regardless of the existing rotating allocation system designated by a local fishery cooperative association. The rotating allocation of oyster-farming spots is carried out by a ballot every three years, so that farmers ensure the equity of access to multiple farming grounds where the influx of nutrients, via run-off and rivers, varies. As a result, the producers reconstructed oyster beds again from the beginning. The height of their oyster fences, from which seed oysters should be exposed to the sun during low tide, had become lower than before. Oyster-seed producers of Higashi-Matsushima, situated along the east side of Matsushima Bay in Miyagi Prefecture, immediately noticed the land subsidence by sight. When the Tōhoku earthquake occurred in 2011, a tsunami up to twenty meters high caused massive ground sinkage. Local producers’ daily practices have been embedded in a series of acute catastrophic events, such as tsunami and the resulting long-term influence on the coastal environment and biological interactions. This work is licensed under a Creative Commons Attribution 4.0 International License.
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