Growth and migration of the roughskin sculpin, Trachidermus fasciatus, in the Kashima River, Kyushu Island, Japan

Abstract

The growth and migration of the roughskin sculpin, Trachidermus fasciatus, were investigated using a mark-recapture method. Samples were obtained by casting net, hand net and trap at sites 0-7 km upstream from the estuary of the Kashima River, in 1993-1996. A total of 1, 029 individuals were marked, 75 being recaptured 105 times in total. Seasonal changes in the total lengths of captured and recaptured individuals indicated an annual growth of ca. 130-190 mm TL, with a period of growth stagnation in summer. Because only one population mode was apparent, the sculpin is thought to have a single-year life span. Individuals showed primarily upstream migration between May to July, eleven recaptured individuals having moved upstream during this period. From August to October, almost all recaptured individuals were taken at the same sites, as before, 6-7 km from the river mouth, the species apparently not the migrating long distances at this time. Subsequently, all sculpins disappeared from the 6-7 km sites by December, sixteen individuals recaptured downstream.