A new fish-way, comprising variously-sized bed materials on a gentle slope, established on the Onga River estuary barrage was found to have 69 cobbles and boulders used as spawning nests of six goby species, including a threatened species, during the period from June 2013 to May 2014. Male body sizes were positively correlated with spawning substrate. In addition, wide salinity variations recorded over the fish-way during high tides on either side of spring tide were also implicated in goby spawning site selection.
Vertebral numbers in white-spotted charr (Salvelinus leucomaenis), collected from four streams and two lakes on Hokkaido Island, Japan, were significantly higher in fish from streams flowing into the Sea of Japan compared with those flowing into the Pacific Ocean, a result compatible with previous allozyme studies. White-spotted charr in Lake Shikotsu had the lowest number of vertebrae, possibly resulting from long-term isolation. The maximum difference in mean vertebral numbers among charr populations was 1.6, twice that observed in chum salmon Onchorhynchus keta and a possible reflection of the absence of hatchery programs that can lead to population mixing. It is likely, therefore, that regional genetic structures have been maintained in Hokkaido Island whitespotted charr.