Introduced in Italy in the 1980s for aquaculture enterprises, the red swamp
crayfish, Procambarus clarkii, has invaded many water bodies, giving rise
to breeding populations that now threaten freshwater ecosystems. An underst
anding of the spatial behaviour of this crayfish could be the baseline for
future research aimed at control and management. Following the same pattern
as other freshwater decapods, P. clarkii, studied in an irrigation ditch s
ystem in Florence, Tuscany, displayed stationary phases (several marked ind
ividuals were recaptured in the area) interposed with nomadic bursts of mov
ement (many marked crayfish disappeared). With a few exceptions, nocturnal
activity prevailed in almost all the seasons in two different analysed habi
tats (irrigation ditches and the Massaciuccoli Lake, Lucca). However, in th
e laboratory, locomotion occurred mostly at daytime. Although still prevail
ing, P. clarkii's nocturnal activity appeared puzzling, because some of its
major predators are nocturnal and this species is mostly herbivorous. The
intercalation between stationary and wandering phases leaves open further p
romising studies on social structures in the field.