Daily Spawning and Quality of Eggs in One Female Red Sea Bream Pagrus major

Abstract

Natural daily spawning by one 4-year-old female red sea bream, Pagrus major, was observed. Daily spawning occurred during the period from May 23 to June 27, 1987. The total number of eggs spawned during the entire spawning season and the maximum number of eggs spawned in one day were 1, 900, 000 and 120, 000, respectively. The average rate of fertilization was 91.5% indicating normal spawning behavior, but the hatching rate varied between 24.5% and 98.1%.
Starvation mortality of newly hatched larvae was examined in nine experimental groups according to a time series. Percentage survival was maximal in an experimental group in the middle spawning season between June 6 and June 12. Average diameters of spawned eggs varied between 0.90mm at the beginning and 0.86mm at the end of the spawning season, decreasing with elevation of water temperature, and showed a correlation (r=-0.745) with the water temperature on the day before spawning. The growth of the 4-year-old female during the period from May 18 (pre-spawning) to July 9 (post-spawning) was 2mm in fork length and 25g in body weight, almost the same as that of the male, showing that individual growth was suppressed during the spawning season.