Seasonal and Circadian Foraging Activity of Procambarus Clarkii (Decapoda, Cambaridae) in Portugal

The feeding chronology of Procambarus clarkii has never been described. Consequently, the author (1) presents data on seasonal and circadian foraging activity of this species, (2) tests statistically the observed patterns, and (3) attempts to determine if the foraging periodicity registered here coincides with other rhythms reported elsewhere for this species. Results suggest the existence of seasonal and bimodal circadian foraging patterns. Seasonally, feeding intensity increased over the spring and summer and declined during autumn and winter. Diurnal patterns revealed increased foraging at night and a decrease in the day time. The differences were not significant. Foraging periodicity of P clarkii is coincident with locomotor rhythms and it seems to result from the interaction between specific endogenous and exogenous factors.