Investigation on fecundity and egg size in cultured and natural crayfish population of Astacus leptodactylus Esch. in Bulgaria

摘要

The objective of the present study was investigation on fecundity (pleopodal egg number) and egg size (weight and diameter) of both a cultured and a natural Narrow-clawed crayfish population (Astacus leptodactylus Eschscholtz, 1823). Further the relationship between these features and the body weight and length, and length and width of the carapace was studied. The investigation was carried out in May 2001 on 71 female crayfish, reared in carp ponds and in May 2002 on 60 females from "Piasachnik" dam-lake in Bulgaria. It was found out that the fecundity of the pond-reared crayfish population was 162.7+104.1 pleopodal eggs; the average egg weight was 13.62+1.72 mg and the egg diameter was 2.96+0.2 mm. The fecundity of the natural crayfish population in "Pyasachnik" dam-lake was 200.8+89.2 pleopodal eggs; the average egg weight was 12.36+1.71 mg and the egg diameter was 2.75 + 0.17 mm. There are significant differences between the number of eggs in both investigated populations. The crayfish females from "Pyasachnik" dam-lake have more pleopodal eggs compared to those reared in ponds (P<0.05). On the contrary, the average values of egg weight and diameter of the pond-reared population were bigger (P<0.001) in comparison to the dam-like ones. A low correlation coefficient (r<0.3) was found between the egg weight and diameter and the investigated morphometric body features, but a considerable correlation (0.6