Grown tired of you fish? Drop in the mail box!


Sounds weird? If so you haven´t heard about the ”fish mail box” in Inada Park, Kawasaki, Tama River in Japan near Tokyo. The ”fish mail box” is a 7 meter by 4 meter large concrete water tank that have been placed along the river to give people a place to drop unwanted fish. The goal of the fish box is to prevent people from releasing fish into the river, since foreign species can wreck havoc with local ecosystems.

People are encourage to call before they drop off their pets as fish can die from the shock if not acclimatized correctly, but it is is permitted to just drop off fish as well. People are also encouraged to drop off tropical invasive species they catch in the river in the fish box.

The fish left in these fish boxes are cared for by Mitsuaki Yamasaki, 51, the head of a local river fish association, before they are placed in new homes. The box is receiving about 10,000 fish a year ranging from small fish to large gars.

The Tama River has seen a lot of new species released in it in recent years during which the aquarium hobby has become even more popular in Japan than before. This has in no small part to do with the movie “Finding Nemo”, even if the increase in popularity started before the movie was released. More than 200 species of foreign tropical fish have been found in the Tama River ranging from typical aquarium fish such as guppies and angelfish to less frequently kept creatures like piranhas and arowanas, earning it the nick name the Tamazon River. Some of the tropical species have established breeding populations while others haven´t, but most species can survive the winters by staying near water treatment areas along the river.

Mitsuaki Yamasaki and other members of the local river fish association are afraid that breeding populations of gars will establish themselves in the river since more and more gars are sold and they have been found in the river. Gar species are predatory fish that could have a severe negative impact on native fish such as sweetfish . Gars are likely able to establish breeding populations in a river with the conditions of the Tama River.

It can not be denied that with over 10,000 fish received by one of these fish boxes since it opened the initiative could aid the struggle to prevent invasive species from getting a foothold in local waters, and it might be an idea that deserves being tried in other problems areas around the world, such as Florida. The only question is if projects like this could work with out the devotion and support from people like Mitsuaki Yamasaki, people who are really passionate about what they do.

Any one interested in or planning to start a similar project somewhere else is very welcome to contact us here at AquaticCommunity as we would love to document your work getting the project of the ground and running it. Leave a comment in the commentary field or send an e-mail to