Life History of Shirauo Salangichthys microdon; Salangidae in a Brackish Lake, Lake Hinuma, Japan.

Abstract

Shirauo S. microdon Bleeker: Salangidae is a very popular food fish, inhabiting brackish waters throughout Japan. However, little is known regarding the life cycle of the species. A 2-year survey was conducted to clarify the movement and dispersal of S. microdon throughout its life history in Lake Hinuma, a brackish lake in central Japan. Results of the survey revealed that from emergence in spring to maturation and spawning the following spring, S. microdon was found within Lake Hinuma all year round. Although there are seasonal occurrences of the species in Shimohinuma River, a river flowing out of Lake Hinuma, when the river shows a well-mixed vertical profile, S. microdon was not found in coastal waters adjacent to the lake, disproving any diadromous life history of the species. Comparisons of standard length, body weight and gonadosomatic index of S. microdon caught within the lake and in the river did not show any significant differences. It was concluded that S. microdon is dependent upon the brackish environment, undertaking its complete life history within the Lake Hinuma water system. This small species is one of the few brackish water species in Japanese waters.