Abstract

Several studies have shown that American crayfish species are more active during the day compared to European species. Spinycheek crayfish (Orconectes limosus) are known as an aggressive nocturnal species with higher daytime activity than noble crayfish (Astacus astacus). The aim of the present study was to compare diurnal and nocturnal activity of these two species under laboratory conditions with the use of video recording techniques. Three groups were included: noble crayfish only, spinycheek crayfish only, and a mixture of both species. Substantial differences were found between species. Higher (P < 0.05) diurnal and nocturnal activities were recorded for spinycheek crayfish than for noble crayfish, with spinycheek females being more active than males, and higher (P < 0.05) nocturnal than diurnal activity in noble crayfish when they were kept in same-species enclosures. However, the above activities were modified when both species were kept together, with an increase in diurnal activity noted in noble crayfish, while nocturnal activity was similar between species. A higher activity during the day might influence the vulnerability of noble crayfish to diurnal predators.

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