Catch quantities of the Japanese icêsh Salangichthys microdon (family Salangidae) in the Yoshii and Takahashi Rivers have declined gradually over the past several decades. The migratory history of Japanese icêsh collected from brackish waters in the Yoshii and Takahashi Rivers was examined using otolith strontiumto-calcium (Sr:Ca) ratios of 27 and 25 specimens, respectively. The otolith Sr:Ca ratio of all individuals from both rivers changed throughout the otolith prôles, from the core to the edge, in increments of 1030×10-3, a value intermediate between the ratios otherwise reported for individuals from freshwater (Lake Kasumigaura, 1.24.4× 10-3) and froma marine area (oŠMisawa, 25.332.2×10-3). These results suggested that all specimens collected from the two rivers had scarcely been resident in freshwater or seawater; thus, all the studied ˆsh could be categorized as a non-diadromous form resident in brackish water.
ASJC Scopus subject areas