Application of different incubation methods in freshwater crayfish (pontastacus leptodactylus eschscholtz, 1823) culture and investigation of possibilities to obtain plague-free juvenils

In this study, the determination of the appropriate incubation technique for the production of freshwater crayfish juveniles Pontastacus leptodactylus (Eschscholtz, 1823) in recirculating aquaculture system and also were investigated the possibilities of obtaining crayfish plague-free juveniles. For this purpose, firstly, the efficiencies of maternal and artificial incubation production techniques were compared. Afterwards, it was aimed to eliminate the crayfish plague agent (Aphonomyces astaci) by disinfecting the eggs, which were subjected to artificial incubation, using different concentrations of formaldehyde (1500, 3000 and 4500ppm) and peracetic acid (2, 6 and 10mg/L). In P. leptodactylus juvenile production, the average survival rate (89.12%) obtained with the artificial incubation production technique was found to be better than the averages (18.49-28.85%) of the maternal incubation technique (P<0.001). In the artificial incubation method, the survival rates of the eggs varied depending on the disinfection dose, and the difference between the groups was statistically significant. The highest survival rate in P. leptodactylus juveniles was obtained in the group treated with 3000ppm formaldehyde (90.63%), while the lowest survival rate was found in the control group (77.99%). Again in terms of survival rates, peracetic acid dose applied at 2mg/L concentration (81.11%) was found to be insufficient for disinfection, and 10mg/L peracetic acid (80.08%) and 4500ppm formaldehyde (79.56%) concentrations were found to be high doses for disinfection (P<0.05). At the beginning of the egg disinfection study positive findings were found in terms of crayfish plague agent (A. astaci) as a result of qPCR analyzes, performed on tissue and egg samples taken from crayfish, and it was determined that the agent load in crayfish tissues was quantitatively higher than the eggs (P<0.05). At the end of the disinfection study, homogenizers of stage I and II juvenile crayfish were analyzed by qPCR method and all results including the control group (disinfection not applied) were found to be negative in terms of crayfish plague. As a result, it has been confirmed by this study that crayfish found in natural waters and used in aquaculture carry A. astaci, and these broodstocks die in aquaculture tanks in case of stress, or infect the system water and thus cause production failure. In addition, it has been demonstrated for the first time in our country that crayfish eggs can be manipulated to obtain plague-free juveniles. In order to obtain a large number of healthy P. leptodactylus juveniles, the use of artificial incubation production technique and disinfection of eggs every other day would be beneficial.