Local oyster producers and fisheries experts in Hiroshima Prefecture, Japan's primary oyster-producing region, have observed a decline in oyster growth over the past few decades. The suboptimal growth of oysters is attributed to changes in seawater nutrient composition, and this issue has multiple underlying factors. One significant factor is the alteration of estuarine watersheds dating back to the 1970s, and more recently, the construction of dams in the early 2000s. These changes have hindered the flow of nutrients from the mountains to the sea. Additionally, some fisheries researchers claim that government-mandated sewage treatment, implemented to meet water quality standards nationwide, has led to excessive purification of estuarine waters, contributing to the maldevelopment of oysters.
In this seminar, I illustrate the practice of seafloor cultivation (kaitei kou’un), a method undertaken by members of a local oyster farming cooperative in Hiroshima. This practice aims to reduce organic pollution while improving the uneven distribution of nutrients by disturbing the seafloor's sediment layer and supplying oxygen. I will discuss how this last-ditch effort to address hypoxic coastal waters in post-industrial Japan generates what I refer to as a "makeshift domus." Metabolic thinking, rooted in Marxist-inspired political ecologies, is pivotal for examining their reformation of aquaculture domus — how material entities are networked to redefine, circulate, and transform the social life of humans and nonhumans. The chemical reactions, nutrient cycling, biochemical processes, and intake and output of energy through this seafloor cultivation practice suggest how reciprocal transformations of interspecies relations play a crucial role at the organismal, societal, and planetary scales in the Anthropocene.

Mariko Yoshida is currently an Assistant Professor at the Graduate School of Humanities and Social Sciences at Hiroshima University. Her research is grounded in environmental anthropology’s interdisciplinary engagement with commodity chain analysis, feminist STS, blue humanities, and multispecies ethnography. Her work identifies the trajectory of ecological uncertainty and precariousness surrounding Pacific oyster aquaculture in Japan and Australia, illustrating how unevenly distributed values and meanings of nature have been dealt with by actors including oyster producers, marine biologists specializing in ocean warming and acidification, biotechnological ventures, market distributors, and consumers. With multi-sited and multi-scalar approaches, she researches the political, discursive, and spatio-temporal processes of multispecies assemblages the liquid materiality of coastal waters, in which human entanglements with oysters, viruses, and nonhuman others shift and create new forces and agents. Her recent publications include a journal article “Scaling Precarity: The Material-Semiotic Practices of Ocean Acidification” (2019, Japanese Review of Cultural Anthropology), a book chapter article “Cultivating the Ocean: Reflections on Desolate Life and Oyster Restoration in Hiroshima” (2023, Routledge). Currently, she is working on transforming her dissertation into a book.