Tokyo (Edo), Japan — Edomae sushi tradition; kohada as indigenous Tokyo Bay fish
Kohada (小鰭, gizzard shad, Konosirus punctatus) is considered by serious sushi connoisseurs the most technically demanding fish in Edomae sushi — its small size, oily flesh, and need for precise vinegar marination (shimesaba technique adapted for a smaller, more delicate fish) makes it the benchmark by which Tokyo sushi chefs are professionally evaluated. The fish changes name with size: shinko (新子, summer juveniles, July–August, tiny and extremely expensive for the labour involved) → kohada (autumn, optimal size) → konoshiro (winter adults, less prized for sushi, often prepared differently). The shimesaba-style process for kohada: light salt (20–30 minutes), rinse, then vinegar marination (1–10 minutes depending on desired intensity and freshness) — the window for optimal marination is narrow and requires daily recalibration by the chef as fish condition changes.
Oily, slightly tangy from vinegar, with clean silver-skin fish character; the marination creates a specific combination of soft-raw interior with firmed exterior; the contrast of rice vinegar-acidity against rich fish oil is the defining Edomae flavour
The kohada vinegar-marination window is shorter than shimesaba mackerel — 2–5 minutes is typical for modern light marination ('shimeru' — to close/firm); the fish must be freshest possible (day-of-catch preferred); shinko kohada (summer juveniles) requires up to 8 fish per single nigiri piece — the chef's labour intensity is astronomical; a well-executed kohada nigiri should have a slight translucency in the centre, firm exterior, and vivid silver-and-black striped skin.
The professional order of evaluation at Tokyo's top Edomae sushi bars: begin with kohada (or shinko in season), then shiro-ika (white squid), then hirame (flounder) — these three white/cured fish test the chef's vinegar and knife skills before any premium toppings; Sushi Sho (Yotsuya, Tokyo) is considered the pinnacle of the kohada tradition; shinko season (July–August) is the most expensive time to eat at serious Tokyo sushi — a set featuring shinko can exceed ¥50,000 per person.
Over-marinating kohada until it becomes uniformly white and firm throughout (modern Edomae preference is partial marination — the centre retains some freshness while the exterior firms); using vinegar that is too harsh (sushi vinegar for kohada should be light rice vinegar without additional sharpness); evaluating a sushi restaurant by toro alone (knowledgeable evaluators order kohada — it reveals the chef's real skill level).
Japanese Cooking: A Simple Art — Shizuo Tsuji