Abstract
The reproductive ecology and life history of the Itasenpara bitterling Acheilognathus longipinnis was investigated in a conservation pond in Himi, Toyama, Japan. Based on ovulation and ovipositor length in females, the breeding season of A. longipinnis was estimated as occurring in September and October, peaking in early October. Female A. longipinnis began to mature from ca. 34.1 mm SL. They had large clutch sizes (max 59 eggs), depositing the highly adhesive and comparatively large eggs (3.05 mm3, 3.47 mm major and 1.29 mm minor axis) by means of a short ovipositor (mean 16.2 mm). The embryos lived inside mussel gills until May the following year, at that time emerging as juveniles (9 mm SL) and growing to maturity (co. 35 mm SL) over the next four months. Ca. 800 individuals emerged from host mussels in May 2007. The adult population size was estimated to be 200 individuals in November 2007, comprising 1 (120 fishes) and 2 (80 fishes) age classes, ranging from 31.2-59.0 mm SL. The survival rate of A. longipinnis from May to November (after their emergence from host mussels) was about 15%, confirming the successful role of the conservation pond in maintaining the A. longipinnis population.
