The Life History of the Crayfish Orconectes kentuckiensis in Big Creek, Illinois

Abstract

Orconectes kentuckiensis was studied in Big Creek in southeastern Illinois from March 1972 to September 1975. It was most common in rocky pools where O. placidas was least common. Orconectes kentuckiensis feeds on plants and arthropods and is fed upon by at least two species of fishes. The species lives to a maximum of 2+ years and had survival rates of .280 and .029 for its 2nd and 3rd years. Form I males and females with maturing ovaries were present from July through April. Weight of maturing ovaries was strongly correlated (r==0.97) with female carapace length. Numbers of ovarian eggs ranged from 59-249 and numbers of abdominal eggs ranged from 49 248 ; both increased significantly with increase in carapace length. Mating was observed in October and November and oviposition occurred in March, April and May. Growth of lst-year crayfish occurred during a period of 4.5 months, of adult males during the spring and summer molts, and of adult females during the summer molt. Chela length and abdomen width were sexually dimorphic and exhibited allometric growth. One hybrid, O. kentuckiensis X O. placidus form I male was found.