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Ayu – Japanese Sweet Fish Worth Waiting and Chasing For


In early June, a lot of anglers go to the rivers across Japan.  On 1st June, many waterways commence the fishing season for Ayu, Japanese sweetfish.  It is a small migratory fish that comes back up the river in springtime in abundance – so many that they can be seen from the river banks, splashing about.

Fragrant Fish, Essential for Early Summer

Ayu is a seasonal poetic word for early summer.  It has a distinctive fragrance that can only be enjoyed from fresh catches from clear streams in season.  They are simply grilled with salt on a charcoal fire, finished with pickled stem ginger or citrus fruit.  It is a very popular seasonal dish among gourmets.  Ancient Japanese and Chinese literature called it Fragrant Fish.  Ayu can be found across a broad area of Eastern Asia, but Japan hosts the largest stock, and catches and consumes the most.

Life Cycle of the Ayu – One Year Fish

The lifespan of the Ayu is one year (another name on records is One Year Fish).  Its lifecycle begins in autumn at rivermouths, as eggs are laid in the bed of fine gravels that gently move about with the stream. They hatch in 2 weeks and juveniles venture towards the ocean (in some cases the lake) to spend the winter there, but never too far away from the river.

They grow up to 5 to 10 centimetres by April, and are ready to return to the river from which their parents came. By then, young ones develop round, comb-like teeth perfect for feeding on algae (biofilm) on rocks.  The scene of fish rubbing their heads on rocks, leaving distinctive marks called “Hamiato”, is easy to spot from banks as they swim upstream.

Most of them live in shoals, but some larger ones monopolise small areas of about one square metre around a rock with abundant food.  Their sense of territory is so acute that they slap away any fish that enters.  They develop yellow spots on their green-grey body and are the most prized catch for the anglers.

After spending summer in the mid and upper part of rivers, around September, fully grown Ayu, now putting a shade of orange and black on their bodies, go down towards river mouths to lay eggs on a bed of soft fine gravels.


Unique and Exciting – Fishing the Agile Young Ayu

There are two fishing seasons.  One is in the autumn to catch the fully grown fishes, but it is the early summer that attracts keen anglers across Japan.

The method of fishing Ayu in this season is called Tomozuri.  Anglers use a decoy to catch the large territorial fish, taking advantage of their instinct to attack intruders.  When the skilled fisherman moves his decoy towards a rock, the target splats its body to the lure, and ends up getting hooked.

This technique is one of the most advanced, as anglers have to be able to identify suitable rocks to which the decoy has to be directed and manoeuvred without damage. To allow decoys to move naturally, they need to use fishing rods as long as 10 metres, which is three times longer than standard ones.

The origin of this unique method is said to have developed in the 18th century.  It is not possible to pinpoint the exact place and time, but it is natural for people across the country to think it would be easy to catch, seeing Ayu going up the river, splashing and chasing each other around the surface.

The popularity of this fishing method is seen on a petition in the Edo era (1603-1868), signed by village leaders along the Kano River in Izu (in current Shizuoka prefecture), asking the government to ban Tomozuri as a hobby.  The fishermen, supplying the busy hot spa inns in the area, struggled to catch enough using the traditional method, Yanaryo, because of the boom in Tomozuri in the area.  The wish was granted.  It was and still is an exciting sport, and some professional fishermen also moved in this direction.

Ayu Fishing Enthusiasts in Action for Preservation

In modern days, the stock of Ayu drastically diminished as rivers and harbours were concreted, mainly for flood prevention.  The soft gravels disappeared, as well as rocks and algae in streams.  Alarmed by this, the fishery authorities had to regulate anglers by charging them an entry fee.  They also release young fish in April and May to keep up with the demand.

For the release, the species that usually live in lakes were used because they were more available and laid more eggs.  The difference between lake Ayu and ocean Ayu were initially considered insignificant.  However, the survival rate of lake Ayu released into rivers that flow into the sea is naturally very low.  Following a series of biological findings, the most recent attempts are to restore, or replicate, their habitat to encourage natural increase, alongside with the most similar and resilient type of Ayu.

There are multiple reports of the return of fish and of increases in stock, because of  the restoration and clean-up of ports and rivers and the protection of environments, all of which help to retain the Ayu species, and this traditional feature of Japanese early summer.

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