The range of the invasive rusty crayfish (Orconectes rusticus) has undergone significant expansion throughout the northeastern United States and southern Canada from its native range of the Ohio River Valley. Despite intensive management actions, such as trapping crayfish to lower population sizes and educational programs to prevent new invasions, little progress has been made in preventing the spread of rusty crayfish. Indeed, more knowledge of the ecology and behavior of the rusty crayfish is needed to develop more effective management techniques. In particular, relatively little is known about the dietary requirements and food choices of this species. This study aimed to elucidate the diets of the rusty crayfish and identify the most important food items within their native range of the Ohio River Valley. We predicted that the diets of rusty crayfish undergo seasonal shifts. Specimens were collected monthly from the same stream in Cincinnati, OH, USA over the course of one year. The stomach contents of the specimens were removed and analyzed for diet composition. The percent contributions of various diet items were compared across months and seasons of collection to determine how the diets of the rusty crayfish change throughout the year.
As predicted, the data suggest that rusty crayfish undergo seasonal diet shifts in their native range, likely coinciding with the seasonal abundance of various food resources (e.g., aquatic insects, leaf fall). As expected, detritus was consistently the dominant food item found in the stomachs across collections. Plant tissue, animal tissue, algae, and diatoms were frequently observed in the stomach contents while protozoa were infrequently observed. The percent contributions of animal tissue to the diets of rusty crayfish showed seasonal variation, suggesting that rusty crayfish may be protein deprived at certain times of the year. During months of low animal tissue consumption, high diatom counts were observed, suggesting that rusty crayfish may supplement their diets with less desirable foods at various times of the year. The data collected in this study can better inform managers of the dietary requirements of rusty crayfish in hopes of developing effective management practices for this species.