Helminth Diversity in Freshwater Fish from Khun Thalae Swamp, Surat Thani Province, Thailand

Freshwater wetlands are biodiversity hotspots that support complex ecological interactions, including diverse parasite communities that contribute to ecosystem functioning and food-web dynamics. Despite their ecological importance, helminth diversity in freshwater fish from southern Thailand remains poorly documented. This study investigates the diversity and seasonal occurrence of helminths infecting freshwater fish in Khun Thalae Swamp, Surat Thani Province, Thailand. Fish were randomly collected by local fishermen during the summer (February–April 2020) and rainy (September–November 2020) seasons. A total of 1,065 fish, representing a broad range of freshwater taxa, were examined using standard parasitological techniques. Helminths recovered from external and internal organs were identified to the lowest practical taxonomic level, and infection patterns were compared between seasons. Helminth infections were common in both sampling periods, with a higher prevalence observed during the rainy season. The parasite community comprised representatives of all major freshwater fish helminth groups, demonstrating considerable taxonomic diversity and a broad host range. Differences in infection patterns among fish hosts and between seasons suggest that environmental conditions and host ecology influence the structure of the parasite community within the wetland ecosystem. This study provides the first comprehensive assessment of helminth diversity in freshwater fish from Khun Thalae Swamp and establishes an important baseline for future ecological and biodiversity research in southern Thailand. The findings highlight the value of parasite diversity as an integral component of freshwater biodiversity and emphasize the importance of conserving wetland ecosystems that sustain both host and parasite communities.