Japan is surrounded by the sea. It also has many rivers. So fishing is a very popular hobby throughout the country. From early summer, fishing for sweet smelt, or ayu, attracts many Japanese fishermen. Fishermen can be seen holding fishing rods and watching for ayu at rivers all over the country. This is one of the events of early summer in Japan. Ayu lay their eggs in the lower course of a river in late fall, and then the hatched ayu swim down to the ocean. They stay in the ocean and then come back to the river as young adults the following spring. They continue to mature in the river throughout the spring and summer. After they spawn in fall, they die. Amateur fishermen fish for ayu with a live ayu decoy in the early summer. This type of fishing, called tomozuri, challenges amateur fishermen, because it is quite difficult. Because of their value, popularity, and scarcity, ayu fishing is controlled by local fishery guilds in most rivers. Amateur fishermen have to pay a fishing fee to the guild. Many guilds release farm-raised ayu into rivers to attract amateur ayu fishermen.