OBSERVATIONS ON CRAYFISH PREDATION IN NORTHERN NEW YORK

Cambarid crayfish are an important constituent of the freshwater communities of northern New York. These decapods can be found in the streams, rivers, and lakes of the Adirondacks and the St. Lawrence River Valley. As foragers, crayfish are flexible in their diet, but they are known to prey on hard-shelled mollusks such as gastropods. We observed three durophagous predation techniques; crushing of the prey’s shell leaving nothing but shell fragments, peeling the shell back to the central columnella of the gastropod, and chipping by which the crayfish breaks off bits of shell around the operculum in order to get past it to the soft body. These types of predation are well documented in marine arthropods, but have received less attention in freshwater ecosystems.

In feeding experiments, we document the durophagous predation traces of the crayfish Cambarus bartoni and Cambarus robustus on the gastropods Viviparus geogianus from the Oswegatchie River in St. Lawrence County, NY. Subsequently, we compare these organisms’ interactions with the predatory behavior of an invasive crayfish species Procambarus clarkia.

All examined crayfish attempted to prey on their gastropod prey. Failed predatory attacks chipped the outside of the aperture and leave characteristic scars on these gastropods comparable to the predatory trace Caedichnus. We found that the larger the size of the prey in relation to the predator, the more frequently chipping of the shell at the aperture occurs; a reverse trend can be observed for peeling.

Larger crayfish tend to have a greater predator to prey size ratio. This size difference allows them to peel their prey’s shell, which is a faster and more effective predation method than chipping. Thus, if larger crayfish species like P. clarkii invade a river, their more effective peeling predation technique may reduce gastropod populations and native species of crayfish could be outcompeted for food resources.