The Reprodudtion and Condition Factor of Rose Bitterling in Shin Tone River

Abstract

The spawning season of rose bitterling Rhodeus ocellatus ocellatus was confirmed to be from April to September with a peak between April and June. Most females mature at 24mm SL. There are more females than males in almost all the total monthly samples. Average counts of eggs in ovary to be shed in size groups 20-30mm, 30-40mm, and greater than 40mm were 17-27, 26-40, and 43-69 respectively. The potential annual mean fecundity was estimated as about 700 eggs in 1981.
Fish of the same length weighed more in summer than in winter. Condition factor also showed higher values in summer. Seasonal fattening cycle was observed between February and December in 1981. Unlike many temperate fish species where fattening cycle has an inerse relationship with gonadal cycle, the body lipid content of this fish, after an initial increase before the start of spawning, stays high throughout the spawning season and drops low at the end of the spawning season. Young, small fish were found to have little lipid reserve at the start of winter while larger fish increasingly recovered their lipid reserve soon after the end of spawning. The smaller fish are assumed to be in a less advantageous situation to pass the winter.