Growth, Length-Weight Relationships, and Condition Associated With Gender and Sexual Stage in the Invasive Northern Crayfish, Orconectes virilis Hagen, 1870 (Decapoda, Cambaridae)

Abstract

The northern crayfish, Orconectes virilis Hagen 1870, is an invasive species in North America and Europe and is currently expanding its range and influence ecologically and globally. Growth patterns and relationships of body morphometrics were evaluated to understand basic life history relationships. Growth and size relationships are provided for gender, sexual phase distributions for adults and juveniles, and chelae length and width relationships to interpret information on sexual dimorphism. The length-weight relationship for the male form I (y = 3.048x - 3.659, r² = 0.945, F = 839.2, p = <0.001), and male form II (y = 3.228x - 3.950, r² = 0.958, F = 1008.6, p = <0.001) sexual reproductive phases; and female (y = 3.071x - 3.734, r² = 0.948, F = 1848.8, p = <0.001), showed positive Fulton Condition Index allometric rates of change with increasing length, while juveniles (y = 1.137x - 1.544, r² = 0.784, F = 345.1, p = <0.001) showed negative allometric change. Carapace width (y = 0.4902x - 0.3973, r² = 0.971, F = 4.039, p = <0.001), carapace depth (y = 0.4767x - 0.1899, r² = 0.980, F = 4.311, p = <0.001), abdomen width (y = 0.4244x -0.4099, r² = 0.956, F = 5.308, p = <0.001), chelae width (y = 0.3011x - 1.0863, r² = 0.787, F = 8.675, p = <0.001), and chelae length (y = 0.705x - 2.1319, r² = 0.880, F = 1.770, p = <0.001) all grew allometrically with respect to carapace length. Based on northern crayfish rapid growth and large size, a competitive advantage during invasion is attained by adults based on larger CL sizes and sexual dimorphism in male chelae size.