Ayu (sweetfish)

A slim, olive-gold fish with a small fatty (adipose) fin like a trout's, a big yellow spot behind the gill and yellow-edged fins. Its teeth are flat combs for scraping algae off rocks. Smells like watermelon or cucumber when fresh, which is why it's called sweetfish.

6–10 in.

About 1 ft, rarely more.

Algae scraped from river rocks; young fish eat plankton and insects.

Lives just one year: hatches in autumn, spends winter at sea or in a lake, runs up the river in spring and spawns and dies the next autumn. Adults guard a feeding territory on a rock and chase away other ayu, which is the basis of tomozuri (decoy) fishing.

Found from Japan & South Korea and China, Hong Kong & Taiwan. Clear, rocky rivers of Japan, Korea, China and Taiwan; Japanese rivers like the Nagara, Shimanto and Kuma are famous, and Lake Biwa has a landlocked form.

Clear, rocky rivers of Japan, Korea, China and Taiwan; Japanese rivers like the Nagara, Shimanto and Kuma are famous, and Lake Biwa has a landlocked form.

1–5 ft in riffles and runs.

1–4 ft over clean, algae-covered rocks.

River seasons open around June 1 in most of Japan and run to autumn; best in July and August.

Daylight hours, especially early morning and late afternoon.

No tide in fresh water; rising or steady water levels after rain are usually best.

Sunny summer days with clear water and good algae growth.

A live decoy ayu (otori) rigged on a nose ring for tomozuri; no bait for territorial fish.

Small fly hooks (kebari) and, where allowed, special ayu lures that imitate an intruder.

Very long, light telescopic ayu rods (27–30 ft) for tomozuri; light fly or tenkara rods for kebari fishing.

Special ayu snag-hook clusters (kake-bari) that catch the attacking fish.

Very fine metal or fluorocarbon lines (0.1–0.3 Japanese size).

Fine fluorocarbon.

In tomozuri, a live decoy ayu is guided into another fish's territory; the owner attacks it and is hooked on the trailing hooks. Buy decoys from shops by the river.

Ask the local tackle shop which rocks are "shining" (freshly grazed); that's where the territorial ayu are.

Catch and release: wet your hands, keep the fish in the water when you can, and release it quickly. Use circle hooks and a dehooker.

Excellent eating — one of the best-tasting fish in its range.

Bleed and ice it right away. Fillet, then remove the skin and any dark bloodline.

A summer delicacy in Japan: salt-grilled whole (shioyaki), eaten head to tail.

Wading fast rivers in summer: wear proper wading shoes and a life vest, and watch for sudden water rises from dam releases and storms.

Ayu fishing requires a special (often pricey) ticket from the local fishery cooperative, and each river sets its opening day, methods and limits. Check local rules. Sea fishing in Japan and South Korea needs no license for visitors, but local fishery cooperatives set rules; rivers and lakes require a day or season ticket (in Japan, a yugyoken) from the local fishery cooperative, and many rivers have closed seasons.

Many rivers restock ayu every spring; follow the cooperative's limits.