Sakhalin Taimen (Ito)
Sakhalin taimen, or ito in Japanese, is a rare species of salmon and the largest freshwater fish in Japan. As well as Hokkaido, they are also found in Sakhalin and the Kuril Islands at the extreme east of Russia. In the past, enormous Sakhalin taimen up to 2 m long were believed to have lived in Lake Shirarutoro and the Akan River in the Kushiro Marsh. Shrouded in mystery, Sakhalin taimen are extremely timid and are very rarely seen by humans, despite being known to ferociously prey on other animals. In recent years, the Sakhalin taimen has experienced a dramatic decrease in population due to overfishing and habitat destruction. In particular, the damming of rivers prevents them from being able to swim upstream to spawn. They were categorized as a Ministry of the Environment Red List endangered species in 2003, and in 2006 the International Union for Conservation of Nature (IUCN) listed them as a critically endangered species facing a high risk of extinction in the wild.
Diet
In the Ainu language, Sakhalin taimen are called chirai. According to Ainu legend, this fish was so powerful it could attack bears and deer, and stop a river’s flow. The Japanese name, ito, is written using the Chinese characters for “fish” and “demon.” In reality, during their first one to two years of life the fish primarily eat insects and aquatic invertebrates. As they mature, they transition to a fish-based diet, consuming finfish and crustaceans. Finally, when they become fully grown, they begin to prey on larger animals such as frogs, mice, and snakes.
Growth
In the springtime, female Sakhalin taimen that have reached 60 cm in length go through their first egg-laying phase, producing approximately 2,000 eggs. After spawning, the eggs take two months to hatch. These are slow-growing fish; it takes one year for the young fish to grow approximately 7 cm in length, and three years for them to reach about 20 cm. On average, they will eventually exceed more than 1 m in length.
Spawning
Male Sakhalin taimen take four years to reach sexual maturity, while females take six years. The average life span is between fifteen to sixteen years. From early to mid-April, mature fish swim up tributaries to spawning grounds. As the fish struggle upstream, the males undergo a striking color change, turning bright red. After mating, the females lay eggs five to six times in spawning nests in the gravel riverbed. Unlike other varieties of salmon that die after laying eggs, Sakhalin taimen spawn many times during their lifetime.
