First collection of amphidromous goby post-larvae of Sicyopterus japonicus in the ocean off Shikoku, Japan

摘要

The oceanic early life of Sicydiinae gobies has remained mysterious although considerable knowledge has been accumulated about their freshwater life. Two marine post-larvae of Sicyopterus japonicus, were collected by otter trawl in the ocean off Shikoku, Japan on 18 July and 22 August 2007. These specimens were identified as S. japonicus using meristic characters and the 16S ribosomal RNA mitochondrial gene, which were compared to S. japonicus adults and two other species of Sicydiinae gobies. Morphological observations documented that S. japonicus post-larval characters were the presence of a red pigment at the bases of the second dorsal and caudal fins in fresh samples, as well as the pres-ence of melanophores on the upper jaw, caudal fin base and the lateral body posterior to the anal fin base. Otolith analysis showed that their post-larval durations were 278 and 286 days, and their birth dates were 13 October and 9 November 2006. It is likely that these two post-larvae may have been transported by the Kuroshio Current from the southern part of their geographic species range such as from Okinawa or Taiwan and may have had recruited to a river around Kochi.