Detailed Studies on the Invasive Alien Species of Procambarus clarkii in Chudong Reservoir, with Morphological Characteristics Compared to Korean Freshwater Crayfish

In this study, we conducted a detailed investigation of the invasive Procambarus clarkii (Girard, 1852), focusing on benthic macroinvertebrates in the Chudong Reservoir from November 2022 to October 2023. The investigation included an analysis of the length-weight relationship of P. clarkii and a comparison of the morphological characteristics of invasive and native crayfish species. The results revealed 53 individuals of P. clarkii (37 adults and 15 juveniles) from the Chudong reservoir. The population of P. clarkii increased during March-July, followed by a decline during August-October, during which the species continued to appear.Overwintering occurred in both adult and juvenile crayfish near rice fields around the reservoir. The length-weight relationship in- dicated positive allometric growth, expressed as W= 3L3.5715. The investigation collected a total of 39 species of benthic macro- invertebrates (1,007 individuals) belonging to 25 families, 11 orders, 4 classes, and 3 phyla at the study sites. Aquatic insects (29 spp., 665 individuals) was the most species-rich group, followed by Mollusca (3 spp., 126 individuals), Malacostraca (3 spp., 210 individuals), and Annelida (3 spp., 6 individuals). The dominant species was Cloeon dipterum (Linnaeus, 1761) (Ephemeroptera), fol- lowed by the subdominant Palaemon paucidens De Haan, 1884 (Decapoda). Benthic macroinvertebrates exhibited increased abun- dance and species richness in May and October, reflecting seasonal patterns similar to the variations in P. clarkii populations. Morphological comparisons were conducted between the invasive species (P. clarkii and P. virginalis) and the native Korean crayfish (Cambaroides similis). Key characteristics, such as body length, coloration, patterning, carapace, rostrum shape, and the presence of an areola on the carapace, were documented to differentiate the species. This study provides foundational data on the seasonal occurrence and habitat characteristics of P. clarkii in South Korea, as well as the key morphological features of alien and native cray- fish species. These results are expected to contribute significantly to the management and control of invasive crayfish species and the conservation of freshwater biodiversity in South Korea.