Freshwater Crayfish 12(1): 430-448 (1999)
PEER REVIEWED RESEARCH ARTICLE
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Life cycle and life history of Astacus leptodactylus in Chatzensee Pond (Zürich) and Lake Ägeri, Switzerland
Astacus leptodactylus was introduced into Swiss waters decades ago. Today big populations can be found in many lakes and ponds. Often they occur together with native or other introduced crayfish species. We suppose that A. leptodactylus may displace Astacus astacus and probably also Austropotamobius torrentium from ponds and lakes. I investigated the life cycle and life history of A. leptodactylus in a pond and a lake (Chatzensee Pond, Lake Ägeri) in Switzerland. The two populations were monitored monthly by SCUBA-diving and reproduction, growth and activity characteristics were recorded. The sex ratio in both populations was 1:1. Females had activated glair glands at the end of September. The mating took place in the second half of December at a temperature of 3.5 to 6 °C. The females spawned at the end of December and carried the eggs until the end of May in Chatzensee Pond and until mid June in Lake Ägeri. The average incubation time of the eggs was 151 days for the population in Chatzensee Pond and 172 days for the population in Lake Ägeri. The size of the smallest mature female was 34 mm carapace length (CL). 100% maturity was found at a size of 43 mm CL in Chatzensee and 46 mm in Lake Ägeri. The average number of eggs per female was 173 in Chatzensee and 180 in Lake Ägeri and varied between 60 and 400 eggs per female. The egg size varied between 2.34 mm and 3.33 mm with an average egg diameter of 2.77 mm in Chatzensee and 2.76 mm in Lake Ägeri. Bigger females had more and bigger eggs. A. leptodactylus was found to be active day and night. Day activity was high during the mating season in December and low in late winter and spring. In May, July and October the crayfish were mainly active during the night. The males moulted in May and the females later after hatching of the juveniles in June (Chatzensee) and at the beginning of July (Lake Ägeri). The second main peak of moulting was in September. In their first year juveniles reached an average size of 19.5 mm CL in Chatzensee Pond and 19.8 mm CL in Lake Ägeri.
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Stucki TP. (1999). Life cycle and life history of Astacus leptodactylus in Chatzensee Pond (Zürich) and Lake Ägeri, Switzerland. Freshwater Crayfish 12(1):430-448. doi:
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