2015 Volume 21 Pages 43-48
Although fish habitat investigations were conducted before Pirika Dam was completed (1977-1982), under dam construction (1983-1989), after Pirika Dam was completed (1990-2004), and after fishway was completed (2005-2014), the impact of the dam project on fish has not been comprehensively evaluated post- under-after dam and fishway construction. Therefore, the results of previous investigations for 38 years on masu salmon population, spawning bed distribution, population density of juveniles and number of fish migrating upstream were evaluated. It was found that masu salmon have been stably inhabiting reaches downstream of the dam for a long period. Although fish fauna, spawning bed distribution and juvenile population density upstream of the dam were found to be reduced after dam construction, all these were restored after fishway installation. Every year (after 2007), about 40 to 150 adult masu salmon migrate upstream past the dam to spawn. The fishway at Pirika Dam was found to be able to reverse the divided connectivity that was created by the dam.
