PREDATORY BEHAVIOR OF NATIVE NORTHERN NEW YORK CRAYFISH VERSUS THEIR RUSTY CRAYFISH COMPETITORS

Invasive crayfish species pose a significant environmental threat, disrupting freshwater ecosystems and challenging the habitats of northern New York. Among these invaders, the rusty crayfish (Procambarus clarkii) is particularly concerning due to its larger size compared to native species, its capacity to destroy aquatic plant beds, prey on fish eggs, and outcompete local crayfish populations. While not yet reported in northern New York, this species has already established itself in regions south, east, and west of the Adirondack Park, as well as spreading northward into Ontario, Canada, for decades.

In this study, we investigated the predatory behaviors of invasive crayfish and compared them to two native species, Cambarus bartoni and Cambarus robustus. We hypothesized that invasive crayfish exhibit more aggressive and destructive behaviors than their native counterparts. Feeding experiments included two prey types: the gastropod Viviparus georgianus and the freshwater clam Elliptio complanata. Predation behaviors were categorized as peeling, crushing, or chipping (the latter representing traces of unsuccessful predation attempts).

The average size of native crayfish was 3.8 cm, while invasive specimens averaged 4.5 cm. Gastropod prey measured 1.3 cm on average, and bivalves were 4 cm in length. Preliminary findings indicate that invasive crayfish consumed more prey and had higher predation success rates (75%) compared to native species (57.9%). Peeling was the most common predation method for both groups: native crayfish peeled 36.84% of their attempts, while invasive crayfish peeled 54.7%.

Notably, while no successful predation on bivalves was observed, invasive crayfish attempted to pry open clams, causing damage to shell margins. In contrast, native crayfish did not engage with bivalve prey. These observations suggest that invasive crayfish are more aggressive and interact with prey items even when predation is unsuccessful, potentially increasing their ecological impact.

Our findings highlight the significant threat posed by invasive crayfish to northern New York ecosystems, emphasizing the urgency of proactive management strategies to mitigate their spread and impact on local communities.