Effects of the presence or absence of males throughout spawning and maternal incubation on the reproductive efficiency of astacid crayfish (Austropotamobius pallipes) under controlled conditions

The separation of females and males after mating is a usual practice when t he reproductive phase of astacids takes place under controlled conditions a nd is carried out to avoid egg losses due to male disturbance during spawni ng and embryonic development. In order to determine the possible effects of male presence on reproductive efficiency, two treatments were tested in th e white-clawed crayfish (Austropotamobius pallipes): females alone, and fem ales and males together throughout egg laying and embryonic development, re spectively (mean female carapace length = 36.35 +/- 0.57 mm). The mating pe riod lasted 19 days. The overall rate of insemination was 98.3%. After 200 days of the experiment, a similar average number of stage-2 juveniles per f emale was obtained in the two treatments: 48.9 +/- 7.1 in females alone and 46.3 +/- 5.9 with males. In view of the difficulties in separating males a nd females, and the apparent lack of effect on reproductive efficiency, con tinued use of the practice should be reconsidered.