Social relationships play a pivotal role in agricultural systems because they influence the economic behavior of stakeholders, but sociological studies aimed at understanding these links have until now not focused much on aquaculture. Here we examine how social capital among communities of the Pampanga River delta in the Philippines plays out in the conduct of aquatic livestock breeding, harvesting, and trading, and how it either facilitates or restrains the transformation of individual livelihoods. Relying on a mixed method of field surveys, participant observation, and questionnaires, we construct an ethnographic portrayal of how the main categories of stakeholder involved in aquaculture (from livestock producers to traders via landless gleaners) elaborate strategies to access or control aquaculture-related resources. We show that the bonding and bridging efforts to construct social capital are strongly embedded in the cultural matrix, and that they are limited by environmental constraints (ecosystem carrying capacity, exposure to natural hazards) and shaped by historical legacies. The resulting pattern of social interactions is overall successful at buffering the negative impact of external forcing factors such as environmental hazards and global market crashes, but we also show how the different outcomes of social exchange are nonetheless unevenly distributed across the spectrum of stakeholders.