Our paper contributes to Science, Technology and Society scholarship on the practices and technologies of containment. We build on existing work in STS that has analyzed containment as a performative sociotechnical system that generates and sustains new realities, new systems, and new relationships. Our contribution draws from the problem of containment in salmon aquaculture. The stakes for containing salmon are very high. Farmed salmon escapes are environmentally damaging to ecosystems and wild salmon populations, and they put additional pressure on an (...) industry that has a very poor environmental record. We consider in detail Newfoundland and Labrador’s “Code of Containment” that works to keep farmed salmon in cages and prevent them from escaping into the wild. Through our analysis of the Code, we argue that containment is not only about holding inside. It is also about holding together, an obsolete meaning of the term “to contain.” We add to STS scholarship by arguing that containment and its associated Code in Newfoundland holds together a large scale, industrial aquaculture sector that tolerates persistent farmed salmon escapes into the wild from ocean-based cages. We conclude by examining the broader implications of our analysis for STS scholarship on the practices and technologies of containment. (shrink)