Linking Supply-Chain Route Structures and Functional Activity Allocation to Identify Sustainability-Relevant Assessment Points in the Bandon Bay Blue Swimming Crab Chain, Thailand

The Bandon Bay blue swimming crab supply chain in Surat Thani Province, Thailand, comprises multiple actor levels and operational activities whose locations do not necessarily correspond to actor labels. This study analyzes supply-chain route structures and functional activity allocation in the chain documented during 2018–2019 as a historical, multi-source descriptive case study. Data were collected from 400 fisher households, 17 collectors or buying stations, two processing plants, and downstream actors through questionnaires, interviews, field observations, product-flow tracing, small-group meetings, and secondary data. The analysis identified 17 routes and compared them across four structural configurations: direct-market, collector-led, processor-linked, and extended market-linkage configurations. Five activity groups were examined: aggregation and product flow, sorting and pre-delivery handling, transportation and delivery coordination, product transformation, and market linkage. The findings show that actor position and functional scope do not necessarily correspond on a one-to-one basis. Collectors performed a broad midstream role involving aggregation, handling, delivery coordination, market linkage, and, in some cases, product transformation. Reported constraints were associated with aggregation, handling, data systems, product transformation, and labor. The study provides a diagnostic route–activity framework for identifying sustainability-relevant assessment points, traceability-readiness needs, monitoring items, and intervention-readiness locations in multi-actor seafood supply chains, rather than measuring sustainability performance directly.