Spring breeding of a northern temperate crayfish, Orconectes rusticus

In southern Ontario in the springs of 1980, 1981, and 1982 the crayfish Orconectes rusticus bred explosively when water temperatures rose above 4 °C. Copulations occurred frequently as sexually mature males and females wandered over the substrate at night. Males fought with each other and interrupted copulating pairs. In 1980 and 1981, females began to sequester themselves and extrude their eggs 11–12 days after copulations began. Males then gradually wandered and fought less, began feeding, and the breeding period ended approximately 4 weeks after the initiation of frequent copulations. In 1982, a delayed spring resulted in a far shorter breeding period. Laboratory experiments indicated that although a rise in water temperature initiated breeding events, including egg extrusion, the degree of necessary temperature increase may be inversely correlated with the duration of lengthening photoperiod to which females are exposed. Females which did not copulate in spring extruded eggs which were mostly infertile, emphasizing the importance of spring copulation in this northern orconectid.