Japan — freshwater fishing traditions of mountain river regions; Gifu prefecture's cormorant fishing (ukai) for ayu is documented since at least the 7th century CE
Ayu (sweetfish, Plecoglossus altivelis) is one of Japan's most celebrated seasonal fish — a small freshwater fish that migrates from sea to rivers in spring and is consumed through summer before spawning in autumn. The name 'sweet fish' refers to the remarkable watermelon-like aroma of the fresh fish and its delicate, slightly sweet flesh — a scent and flavour impossible to describe adequately and unforgettable once experienced. Ayu are caught by traditional fishing methods including a fishing-lure technique called tomozuri (using a tethered live ayu to attract others, since ayu are highly territorial and attack competitors) and fishing by hand from rocky mountain streams. The fish is almost always cooked whole — salt-grilling (shioyaki) is the canonical preparation, where the fish is salted heavily, skewered on stainless steel or bamboo to suggest the swimming posture (naminari no kushiuchi — wave-form skewering), and grilled over charcoal until the skin is crisp and the interior just cooked. The proper eating method is to eat the entire fish including head, fins, tail, and intestine (hara-wata) — the bitter intestines are considered a delicacy, the culinary complement to the sweet flesh. Premium ayu from clean, fast-flowing rivers (Yoshino-gawa in Nara, Shimanto-gawa in Kochi, Nagara-gawa in Gifu) command extraordinary prices. Ayu season defines summer dining in Japan's inland regions.
Fresh wild ayu is one of the most specific flavour experiences in any food culture — the watermelon-cucumber aroma is immediately identifiable, the flesh sweet and delicate, the slight bitterness of the intestines providing a counterpoint that makes each bite a complete flavour statement.
Salt application technique: heavy salting on the fins and tail (which burn more easily) with moderate salting on the body — creating a visual salt-flower effect on the fins while keeping the flesh from over-salting. Skewering in the wave form preserves the fish's natural silhouette and prevents steam from being trapped. High, direct charcoal heat (binchotan ideally) for relatively brief cooking — ayu is small and cooks quickly. Immediate service — ayu's delicate fat deteriorates with standing.
The test for perfectly cooked ayu: press the body gently — it should yield slightly but spring back. The eyes should turn white. The head should be edible without being charred to unpleasantness. Press the fish before and after salting to understand the moisture reduction the salt creates on the surface. For the best experience, seek ayu from specialist river fisheries rather than farmed ayu — wild fish from clean, fast rivers have the watermelon aroma; farmed ayu raised in still ponds often lacks this characteristic entirely. Pair with tade su (smart-weed vinegar) — a specific Japanese seasonal condiment made from the tade herb (water pepper) that is the traditional accompaniment to ayu.
Over-cooking causes the delicate, sweet flesh to become dry and the characteristic watermelon aroma to dissipate. Skipping the fin-salting creates burning and charring on the most exposed parts. Removing the intestines before cooking or eating — the bitter hara-wata is integral to the full ayu experience and contrasts the sweet flesh purposefully. Cooking ayu from the refrigerator rather than room temperature — cold fish shocks on contact with grill and cooks unevenly.
Kaiseki: The Exquisite Cuisine of Kyoto's Kikunoi Restaurant — Murata Yoshihiro