Helminth absence and invasion success of blackchin tilapia (<em>Sarotherodon melanotheron</em>) in Thailand

Introduction: This study investigates the helminth absence in the invasive blackchin tilapia (Sarotherodon melanotheron) in Thailand, testing the Enemy Release Hypothesis (ERH). The ERH suggests that invasive species thrive in new habitats due to the lack of natural parasites that control their populations in native environments. The recent introduction of S. melanotheron in Thailand has raised concerns about its ecological and economic impacts. Methods: We surveyed 164 blackchin tilapia from six different locations in Chumphon Province, Thailand, including the sea, estuary, canal, and shrimp farms, examining them for helminths. Fishermen provided data on the first capture dates in the surveyed areas to determine how long the populations have been established. Results: No helminths were detected in any of the examined fish. The absence of parasites was consistent across all surveyed environments, suggesting a lack of parasitic burden in the population. Discussion: The absence of helminths may contribute to the successful expansion of S. melanotheron in Thailand, supporting the Enemy Release Hypothesis.