Comparison between individual and group mating of Austropotamobius pallipes under controlled conditions

Individual mating was compared with mating in groups under laboratory conditions using 64 females and 32 males of white–clawed crayfish (Austropotamobius pallipes). Mating in groups took place at a density of 24 animals/m 2 placed in two 1 m 2 fibreglass tanks (16 females and 8 males/tank). Individual pairing was made in net plastic cubic boxes of 0.25 · 0.25 m bottom surface placed in 1 m 2 fibreglass tanks (8 boxes/tank). Percentages of mating and spawning were similar in both treatments (100 and 93.7% in groups and 96.9 and 93.7% in individual pairing). However, pleopodal egg number and survival rate 78 days after spawning (phase VIII-IX of embryonic development) were higher in females mated in groups (67 and 57.4%) than those individually inseminated (26 and 25.9%). Possible causes of lower egg survival rate of individually mated females are discussed.