Ayu
Plecoglossus altivelis
Ayu (sweetfish) is an East Asian amphidromous fish that moves between coastal waters and rivers, then lives and feeds in clear streams. It is prized as a table fish and an important seasonal catch where native or stocked.
Identification points
- Slender, laterally compressed body with a distinctly arched back
- Small, silvery-golden fish with a yellowish fin tint and a forked tail
- Mouth and teeth adapted for scraping algae, giving the head a small, pointed look
Habitat
Clear, cool rivers and streams with moderate current, especially riffles and runs over cobble or gravel; juveniles may occur in coastal waters and estuaries before moving upriver.
Bait notes
Traditional baits include natural algae, sweetfish paste baits, and small bits of shrimp or worm where allowed. Small spoons, tiny spinners, and micro flies can work, but bait-and-rod fishing is more common than lure fishing in many areas.
Behavior
Ayu graze on algae and diatoms scraped from rocks, which makes them territorial and often hold small feeding stations on current-swept stones. They bite best during warmer months and may school in river sections with good flow and sunlit algae growth.
Caution
Regulations vary widely and some fisheries are tightly controlled; check local seasons, gear rules, and stocking restrictions. No major species-specific toxin concern is known, but avoid eating fish from polluted rivers.
Fishing notes
Fish shallow runs and riffles where algae grows on stones, using light line and small hooks. Drift presentations near bottom or a slow upstream cast-and-retrieve can work; in Japan, ayu are also commonly targeted by友釣り (tomozuri), using a live decoy fish.