Medicinal leech habitats: important biodiversity hotspots for fish species conservation

Medicinal leeches are known to primarily inhabit shallow parts of wetlands, which have unique physical, chemical, and biological properties that differ from the main bodies of water in these areas. However, limited research has been conducted on fish diversity and abundance in these habitats. This study aimed to investigate the fish diversity and abundance in the wetlands surrounding Lake Eğirdir (Turkey), where medicinal leeches are known to be present, and discuss the importance of conserving these habitats. Common diversity indices were used to estimate species richness, abundance, and biomass. A total of 416 fish from six species (Aphanius anatoliae, Carassius gibelio, Gambusia holbrooki, Pseudophoxinus egridiri, Pseudorasbora parva, and Seminemacheilus ispartensis) were sampled. The results showed that the species richness was lower in the studied wetlands (six species) compared to the lake itself (13 species), with the dominant species in terms of abundance and biomass being G. holbrooki (44.95%) and C. gibelio (33.46%). The presence of invasive and endemic species plays an important role in shaping the diversity and abundance of the fish community. The study found that there is compatibility between fish diversity and medicinal leeches in wetlands, and that fish species and their sizes provide feeding opportunities in favor of medicinal leeches. The wetlands also provide a protected area for the conservation of two IUCN red-listed fish species (P. egridiri and A. anatoliae). Thus, the study highlights the importance of conserving these habitats for maintaining the ecological unity, harmony, and sustainability of both medicinal leeches and fish populations.