Every summer you can see Japanese kids everywhere heading off to their closest park with a pond or stream, armed with their green plastic boxes and nets or with a fishing stick with dried squid bait hanging from it. They are going crayfish hunting. If they carry buckets, they are most likely tadpole fishing as well.

Facts:

Japanese crayfish (Nihon zarigani in Japanese or Cambaroides japonicus – scientific name)

The zarigani are crustaceans (family of shrimps and crabs). They have flat, segmented bodies and five pairs of legs. The first three pairs of legs are spineless claws. The front pair are larger than the rest.

Did you know…

that if the legs or claws get broken off (which sometimes happens when male species fight or when naughty boys tear them off), they are regenerated …which means they grow back again.

Crayfish have a pair of sensory of antennae and two eyes at the end of movable stalks. The body is about 4-5 cm long but may grow up to 7 cm long. They molt and lose their hard outer exoskeletons. When they have just molted, they are at their most vulnerable as predators can easily eat their soft bodies. The bodies grow bigger before their new shell hardens. Crayfish have powerful tails which they will flick in a motion to get away from their enemies.

Distribution: All over Hokkaido and the Tohoku region of northeastern Japan. They live in clean water and hide in holes in stones and hollows in gravel and sand. They don’t like warm water and so are found in the northern parts.

What they eat: Plant and animal matter. Crayfish fancy algae and aquatic plants but will also eat worms, tadpoles, small fish and insect larvae and dead animals.

What eats them: Fish such as bass and trout are their predators.

Crayfish mate from their second year and during the season July to September. The female stores the sperm in a special receptable in her abdomen for use later. She lays her eggs in autumn when she will release the sperm to fertilise her eggs. The eggs stay stuck to the bottom of her abdomen until they hatch in the spring. Females carrying their eggs are said to be “in berry” because the eggs resemble berries.

However, often you will find that the catch is probably not the true-blue nihon zarigani but an evolved hybrid species bred with the American crayfish or Amerika zarigani. Nihon zarigani is a dull mud-like color all through while the American crayfish is a lobster red all over, and the hybrids are anywhere in between probably with red heads and claws.

 

Source of information: “Japanese crayfish” Aug 16, 2002 Japan Times. To read up quick facts about the Nihon zarigani or Japanese crayfish, click here.