Length-weight Relationship, Body Morphometrics, and Condition Based on Sexual Stage in the Rusty Crayfish, Orconectes rusticus Girard, 1852 (Decapoda, Cambaridae) with Emphasis on Management Implication

Abstract

The Rusty crayfish, Orconectes rusticus Girard, is an invasive crayfish species found in the Midwestern United States and Canada. O. rusticus has displaced native crayfish species throughout its range. Length-weight relationship, body morphometric relationship, and condition within the species native range in south-central Indiana were studied. Growth, size relationships based on gender, sexual phase for adults and juveniles and chelae-length, width relationships was used to interpret patterns in sexual dimorphism. Carapace length (CL)–wet weight (Wwt ) relationships for all genders (i.e., male, female, juvenile) and all male forms (form I and II) had positive allometric growth. Native O. rusticus were found to be larger in all measurements and heavier than the O. rusticus collected in the invasive range. Orconectes rusticus has a smaller mean carapace length and had a mean weight less than Orconectes limosus, Procambarus acutus, Procambarus fallax, and Procambarus clarkii. Orconectes rusticus shows strong sexual dimorphism patterns, but compared to other freshwater crayfish it is generally smaller. To establish populations in occupied areas O. rusticus may use a combination of competitive and aggressive behaviors. Orconectes rusticus should be managed with depletion trapping and by restoring native predatory fish populations.