活け締め

いけじめ, いけしめikejime

noun

1. draining blood from a live fish (from above the gills and at the base of the tail) to keep it fresh
2. fasting fish for several days to preserve flavour and quality (and reduce mortality during transport)
3. killing fish in a fishtank (immediately before cooking)
4. fish killed in a fishtank

Study it in Yanamino