The red swamp crayfish, a highly invasive species, prefers decaying submerged plants over living ones. The crayfish showed a strong preference for decaying plants that were 8 or 12 days old. The weight of decaying plants decreased more rapidly than that of living plants. Total phenol content was higher in living plants compared to decaying ones, with Myriophyllum spicatum having the highest content. This study suggests that red swamp crayfish selectively feed on decaying submerged plants rather than fresh ones.