Embryonic development, eclosion and performance of juvenile noble crayfish Astacus astacus (L. 1758) in response to shortened cold period

Abstract

ABSTRACT A suitable temperature regime in artificial incubation of crayfish eggs is crucial for successful application in aquaculture production and conservation projects. We studied the effect of different extended cold periods (CP: 10, 24 and 38 days at 7.5 ± 0.5°C) during artificial incubation on embryonic development, incubation efficiency and subsequent juvenile crayfish performance in noble crayfish. Best results were obtained at 38-day CP with stage II survival rate of 60.4 ± 7.4% and stage II wet weight of 38.4 ± 1.9 mg. This regime synchronized embryonic development and equally reduced hatching and moulting period to 7 days with no overlap between both. Survival was high in a subsequent 100-day rearing experiment (10-day CP: 85.0 ± 9.2%; 24-day CP: 90.0 ± 4.1%; 38-day CP: 92.5 ± 2.9%) and juvenile crayfish from 38-day CP grew faster, but these results were not significant. Staggered response of embryonic development to temperature rise and improved juvenile fitness at longer CP illustrate that dormancy of noble crayfish eggs represents a form of true diapause that is regulated solely by temperature and can be accelerated beyond a threshold only at the expense of higher mortality and reduced juvenile fitness.