EFFECTS OF TEMPERATURE AND FOOD DENSITY ON EGG DEVELOPMENT, LARVAL SURVIVAL AND GROWTH OF PERCH (PERCA-FLUVIATILIS L)

Egg development of perch (Perca fluviatilis L.) at a series of constant temperatures, and larval survival and growth in intensive culture systems at different temperatures and food densities were compared. Hatching was observed within the temperature range of 6-22-degrees-C, with the highest survival between 12 and 20-degrees-C. The longer larvae at mass hatching were found at 12 to 18-degrees-C. In one trial, 4-day-old larvae were fed at 15 and 20-degrees-C with 0, 500, 3000, 6000, 9000 and 12 000 rotifers.l-1 over a 9-day period. A high mortality was observed during the second week after hatching. Survival and growth of larvae at different temperatures and food densities were significantly different. The best survival and growth were observed at 20-degrees-C and 6000 rotifers-l.1. In another trial, 12-day-old larvae were fed at 15 and 20-degrees-C with 0, 50, 100, 200, 400, 600, 800 and 1000 copepodites.l-1 over a 12-day period. Survival rates were similar between both temperatures but growth was significantly better in the warmer water. Survival rates at both temperatures increased with copepodite densities from 50 to 200.l-1. At 200 or more per liter, survival rates were similar, but growth rates were highest at 400-1000 copepodites.l-1 and 20-degrees-C.