Reproductive efficiency of the signal crayfish (Pacifastacus leniusculus Dana. Astacidae) at different densities under both culture and laboratory conditions

Studies carried out to evaluate reproductive efficiency from maturing up to juvenile stage 2 production in astacid crayfish are scarce. Research with a view to determining total losses over the whole reproductive cycle is required. Two experiments were carried out with Pacifastacus leniusculus to obtain data on reproductive efficiency in earthen ponds and under laboratory conditions, in each case with two different densities of animals. All the parameters recorded were related to the initial number of females. In earthen ponds, numbers of egg-bearing females close to hatching (April) showed no significant differences between the two densities (76.1% with 3.4 breeders/m2 and 72.5% with 6.6 breeders/m2), with an estimated mean of 228 eggs per female. In the laboratory, 81.3% and 75% of females yielded stage 2 juveniles at densities of 6 and 12 breeders/m2, respectively, with an average of 135.4 juveniles per initial female, achieving an efficiency from first to final count around 70%. Productivity results are discussed with relation to those attained in other astacid species.