Feeding and gastric evacuation in perch (Perca fluviatilis L.)

PE R CHThe gastric evacuation rate of perch was determined at 17 ± 1°C using 19 the common New Zealand bully (Gobiomorphus eotidianus) , as food.Approximately 16 h were required for 90% evacuation.The gastric evacuation rate decreased exponentially with time after initial ingestion.Force feeding and starvation periods in excess of 7 days reduced the evacuation rate.A mathematical model was developed, using the evacuation rate, to determine diel feeding periodicity.Perch were shown to be most active in daylight hours (88% feeding).Peak feeding times in the Selwyn River, Canterbury during summer were 1100 hand 1900 h.Behavioural observations made in the laboratory and the field indicate that perch are visual feeders and that they can develop searching ima'ges for specific prey.While hunting, the prey attack sequence was initiated when a "critical" distance of 50-100 mm was reached between the perch and the prey.'" -..