GENETIC-STUDIES OF TENCH (TINCA-TINCA L) - INDUCED TRIPLOIDY AND TETRAPLOIDY AND 1ST PERFORMANCE DATA

Triploidy was successfully induced with cold shocks of 0-2-degrees-C, lasting 35 min and starting 2-5 min after gamete activation and with hydrostatic pressure shocks with 1, 2 and 5 min exposure at 50.01-52.47 MPa starting 2-5 min after gamete activation. Tetraploidy was successfully induced with heat shocks of 40.5-degrees-C, lasting 1.5 min and starting 45 min after gamete activation and with hydrostatic pressure shocks starting 50 min after gamete activation without further changes in the remaining parameters. Temperature shocks were considered to be the most suitable treatments, based on observed proportions of viable polyploids and incubation rates. The tau0 unit for tench was used for standardization of shock initiation. Results of rearing triploid and/or tetraploid tench in experimental earthen ponds were assessed. A sample of 19 4-year-old triploid and their 43 diploid siblings was used for analysis of weight differences, gonadosomatic index and dressing percentage. Triploid females displayed 13.52% higher live weight and 3.94% higher dressing percentage than diploid females (P<0.001) and their gonadosomatic index reached 25.10% of that of diploid females (P<0.001). Triploid males displayed 23.66% higher live weight than diploid males (P<0.01). Their dressing percentage was 1.30% lower (P<0.1) while gonadosomatic index reached 60.00% of that of diploid males. Differences in live weight and gonadosomatic index between triploid females and triploid males were found statistically significant (P<0.01 and P<0.05, respectively) while no difference was found in dressing percentage.