Off-Season Spawning of Yellow Perch

Abstract The thermal and light conditions for 2-year-old broodstock of yellow perch Perca flavescens were shifted by 6 months in an effort to change spawning from spring to autumn and fall. The natural photothermal conditions consisted of a chill period of 10°C and 10 h of light during January–March followed by increases in temperature to 20–22°C and photoperiod to 15 h light during July–September. The natural spawning of yellow perch occurs in April–May at 12–14°C and 12 h light. In the present study, the broodstock were maintained at a higher temperature and a longer period of light during September–February (18°C and 13 h light). The photothermal conditions were decreased gradually until June. The chill period (10°C and 11 h light) was 60 d in duration (June–July) and was followed by gradually increased water temperature and longer daylight (12°C and 19 h). Following this period, 50% of the females were fully ovulated, and they were stripped or spawned naturally. The males spermiated during the entire ...