Does rusty crayfish (Orconectes rusticus) ability to resist current differ with home environment

Abstract

Rusty crayfish (Orconectes rusticus) have been invading northern Michigan waterways and displacing native species of crayfish for decades, aided by advantages in aggressiveness and ability to resist current. Previous studies have suggested that organisms of the same species can develop phenotypic differences depending on if they live in lentic or lotic environments. These changes are thought to result from adaptation to the difference in water velocity between the two systems. Our study investigated ability to resist current in O. rusticus from two sources in Northern Michigan, Carp Lake River and Burt Lake. We hypothesized that O. rusticus from Carp Lake River have a better ability to resist currents than Burt Lake O. rusticus. To test this, river and lake crayfish were placed in a propeller-driven laboratory flume and subjected to increasing water velocities in order determine the maximum flow they could withstand. Results from the study suggest no statistically significant difference in ability to resist currents between the two populations. Furthermore, no correlation was found between crayfish length, weight, tail width, and resistance to flow. Lack of a statistically significant difference between the two populations is hypothesized to be due to low water velocities, insufficient time for evolution, or absence of any evolutionary or developmental difference between the two populations.