JUVENILE AGONISTIC BEHAVIORS OF THREE CRAYFISH SPECIES AND THEIR ROLE IN SHAPING SPECIES DISTRIBUTION IN THE MONOCACY RIVER

Abstract

The invasive crayfish Orconectes rusticus was first reported in the Maryland portion of the Monocacy River in 2007. Subsequently, there has been rapid displacement of the dominant invasive crayfish species Orconectes virilis. I tested the hypothesis that the agonistic behaviors exhibited by juvenile 0. rusticus would lead to dominance over 0. virilis and native Orconectes obscurus, and that there would be a nominal difference in the dominance observed between these two species. The results of my laboratory trials suggest that 0. rusticus was not the dominant aggressor; rather 0. virilis appeared to be most aggressive. There was equal aggression displayed by 0. rusticus and 0. obscurus. My findings contest the hypothesis that aggressive behavior in the juvenile life stage contributes to the displacement of other species by 0. rusticus. Furthermore, they suggest that alternative mechanisms are responsible for the successful invasion of 0. rusticus in the Monocacy River.