Effect of crossbreeding three divergent populations on the juvenile production and rearing performance of the redclaw crayfish Cherax quadricarinatus

Abstract

Cherax quadricarinatus populations from different regions in Mexico have been exposed to varying environmental conditions and farming practices resulting in genetic drift. These populations have lost genetic variability due to selection pressure and inbreeding which could decrease reproductive capacity and growth rates. Three divergent groups from Baja California Sur (C), Tamaulipas (T) and Michoacan (M) were crossbred to evaluate the effect on reproduction and production of juveniles. There were no statistical differences in absolute fecundity and number of juveniles between the crosses. However, reference (two origin) and nucleus (three origin) crosses show that fecundity was at the higher end when the M breeder was male. Juvenile weight 45 days post-hatch for reference crosses had a smaller overall mean compared to parental or nucleus crosses. The nucleus crosses CT:M and TC:M showed positive heterosis for fecundity and produced juveniles, when compared to the best-performing parental group (C). After 195 days of rearing, juvenile mean growth for C and T offspring was 2.66 and 1.74 g higher than for M offspring. Reference crosses showed that, when the M breeder is female, body weight and growth rate are at the lower end of the overall range. This may relate to previous selective pressure for growth for the C and T populations. Reference crosses showed that juveniles from female M breeders (M:C, M:T) resulted in mean final weights statistically smaller when compared to the parental C group. Growth heterosis was positive for the nucleus when compared to parental M. A significant positive correlation was found between growth rate and Na (p = .002). A larger gene pool appears to improve adaptation to intensive rearing. Crossbreeding enhanced commercially important traits with the nucleus having similar performance when compared to parental C, while improving observed heterozygosity. The nucleus is suitable to commence a genetic selection program.