Reproduction dynamics of the marbled crayfish Procambarus virginalis Lyko, 2017 from an anthropogenic lake in northern Croatia

Despite the growing number of established populations in Europe, the reproduction dynamics of parthenogenetic marbled crayfish, Procambarus virginalis Lyko, 2017, from populations in the wild is currently understudied. In this study, we performed a systematic seven-month long monitoring of the reproduction dynamics of marbled crayfish population in an anthropogenic lake in continental Croatia. Crayfish were caught monthly by applying the baited stick catch method. We recorded pleopodal fecundity and the number of hatched juveniles in each monthly catch and a random selection of individuals (20 per month) was dissected to determine the ovarian fecundity. Obtained fecundity parameters were correlated with crayfish size (total length, weight and pleon size), body condition (Fulton's condition factor), organosomatic indices (hepatosomatic index: HSI and gonadosomatic index: GSI) and compared with available literature data on marbled crayfish from laboratory-reared or wild populations. Based on the obtained data, we identified two potential reproductive peaks in early summer and mid autumn. However, the continuous presence of individuals with mature ovarian eggs and glair glands throughout almost the entire monitoring period indicates potential reproduction throughout June to November. Ovarian egg number and number of hatched juveniles was significantly correlated with crayfish size and Fulton's condition factor, while GSI exhibited significant variations among analyzed months and was positively correlated with HSI. The number of hatched juveniles in our study was significantly lower compared to literature data for marbled crayfish from populations in the wild and laboratory-reared populations. Collected data offer insights into the understudied reproduction dynamics of marbled crayfish in the wild and represent baseline information for predicting its invasion dynamics and risks of its further spread in this region.