Аge structure and fecundity of the noble crayfish populations in abandoned quarries

Abstract

The population of noble crayfish (Astacus astacus) was researched in quarries of an old brick plant in Molodechno district of Minsk region. Rare disappearing noble crayfish was found in 10 closed quarries. The presence of crayfish in closed quarries that are not connected with watercourses indicates that these populations were created by man. The population of noble crayfish in the quarries of an old brick factory is characterized by a high number. The average catch by eel traps was 1.31 ± 0.77 individuals/trap/day. Crayfish in the first and second year of life grew faster in quarries than in other habitats, but subsequently the average size of individuals in the quarry was smaller in comparison with the general model of noble crayfish growth in Belarus. Individuals that were older than 6 years have not been found in quarries. This indicates that there are factors that determine high mortality rate in older age groups. However, favorable conditions for the growth of juveniles allow the population to maintain their numbers at a high level. The reason for this phenomenon remains unknown. The size of noble crayfish individuals reaching puberty and the fertility is comparable to those from other habitats. In the quarry, the minimum length of an oviparous female was 7.2 cm. Egg-laying females in the 7.0-7.9 cm size class were 16.7 %, in the 8.0-8.9 cm size class - 38.8, in the 9.0-9.9 cm size class - 70.6 %, in the size class of 10.0-10.9 cm all the females were oviparous.The population of noble crayfish from the quarries of Molodechno district should be considered as donor population for carrying out resettlement into the water bodies of the river Neman.