Crayfish (Procambarus Clarkii) Condition Throughout the Year in the Lower Mondego River Valley, Portugal

Abstract

A study was performed to document the seasonality of crayfish (Procambarus clarkii) condition in the lower Mondego River valley, relating it to sex and to reproductive state. Two sampling programs were carried out, and Fulton's condition factor was determined for individual crayfish. The first sampling program was performed from June 1992 to January 1993 and the second from May 1993 to September 1994. Twenty-five baited traps were set overnight, spaced 5 m apart. In 1992-93 a total of 337 crayfish were captured, average post orbital carapace length (POCL) 3.19 cm, average weight 17.18 g and average condition factor 0.49. In 1993-94, 2149 crayfish were captured, average POCL 2.94 cm, average weight 15.39 g and average condition factor 0.54. Reproductively active (Form I) males were abundant from May to October. The average condition factor was dependent on sex and reproductive state, but the seasonal pattern of variation was similar for females, for all males, for reproductive males (Form I) and for non-reproductive males (Form II). Form II males had the lowest average condition factor. Form I males had the highest average condition factor. From December to May there was a gradual decrease in condition, ending as a steep decrease. This may be explained by a mass moulting to reproductive forms. A postreproductive decrease in condition was observed in September and October. Our data corroborate the idea that there is a relation between male condition and reproductive activity.