The Feeding Behavior of the Rusty Crayfish (Orconectes rusticus) in a Simulated Submerged Aquatic Grass Bed Environment

Abstract

Rusty crayfish (Orconectes rusticus) have been known to significantly alter, through consumption and removal, macrophytes or submerged aquatic vegetation (SAV) in streams and lakes they have invaded. The invasion of the 0. rusticus into the lower reaches of the Susquehanna River, combined with their ability to withstand low salinity stresses, creates the possibility they may eventually invade the northern Chesapeake Bay. The potential effects of 0. rusticus on such an estuarine system are unknown. Using microcosms simulating SAV composition of the Susquehanna Flats region of the Chesapeake Bay, I monitored for consumption and removal effects from an 0. rusticus invasion on three species of SAV (Vallisneria americana, Najas guadalupensis, and Myriophyllum spicatum). Microcosms were separated into three treatments: controls, crayfish only, and crayfish with an alternative food source. Three trials were conducted with each trial lasting five weeks. Data show that reduction of biomass to larger species of SAV such as V. americana and M. spicatum was limited, with the exception of the consumption or senescence of V americana flower and bud stems. However, biomass of the smaller sized species N. guadalupensis was almost completely removed. Further analysis looking at gut contents of 0. rusticus reinforced the hypothesis that they will consume Chesapeake Bay SAVs. My data also show that biomass reduction can be related to a seasonal component of crayfish feeding and behavior. Reductions in plant biomass could also be due to indirect effects from the crayfish including increased levels of total suspended solids leading to decreased ambient light levels.