EFFECTS OF EGG BATH AND DAILY REMOVAL OF DEAD EGGS ON HATCHING SUCCESS AND PRODUCTION OF STAGE 2 JUVENILES DURING ARTIFICIAL INCUBATION IN NOBLE CRAYFISH (ASTACUS ASTACUS L.)

Abstract

The effects of egg bath (iodine-detergent preparation) and daily removal of dead eggs on hatching success and production of juveniles in stage 2 were investigated during a short (sixteen days) artificial incubation (AI) of noble crayfish eggs. At the beginning of AI, eggs were in phase XII (pulsating heart appearance) and were incubated in 18 polyethylene 1liter jars (100 eggs/jar, egg density 4.5 eggs.cm-2). Six different treatments were tested during AI: – C: control group without removal of dead eggs and egg bath; – R: daily removal of dead eggs without egg bath; – R-LB: daily removal of dead eggs, low frequency of egg bath (once every five days); – R-FB: daily removal of dead eggs, frequent egg bath (once every three days); – LB: without removal of dead eggs, with low frequency of egg bath; – FB: without removal of dead eggs, with frequent egg bath. Egg bath was performed by iodine-detergent preparation Jodisol (dose 2 ml.l-1 and exposition time 2 minutes). Results showed a better hatching rate after removing dead eggs rather than using the egg bath. Three treatments (R; R-LB; R-FB) showed significantly better survival rates in stage 1 (86.3 ± 5.4%) and 2 (84.2 ± 5.4%) than control (74.3 ± 0.9% and 73.3 ± 0.5%, respectively). Two treatments (LB, FB) showed no statistically different survival rate in stage 1 and 2 (82.5 ± 5.5 and 80.7 ± 5.3%, respectively) than the other treatments. After AI, juveniles from all treatments were reared under controlled conditions. At the end of rearing period, juveniles reached a survival rate of 64.1 ± 0.5% with mean body length of 22.0 ± 1.6 mm and mean body weight of 266.0 ± 50.9 mg. Negative effects of AI on growth and survival of juveniles were not evidenced.

Keywords

• Astacus astacus
• artificial incubation
• jar
• juvenile production