New record and rare occurrence of European eel (Anguilla anguilla) from freshwater bodies in Karaburun Peninsula (İzmir, Türkiye): Anthropogenic pressures on the fish movements

Objective: Fish can be used as bio-indicators to determine whether freshwater habitat has been altered. As habitat discontinuity occurs due to the presence of mechanical barriers, species composition can be altered upstream and downstream. Since the beginning of the 1980s, the amount of European eel Anguilla anguilla entering inland waters in Türkiye and European countries has decreased significantly. Our study describes for the first time the presence of A. anguilla from the freshwater bodies in the Karaburun Peninsula. Materials and Methods: From November 2020 to August 2021, fish specimens were collected through electrofishing in one lotic system and three transitional waters of the study area. Clove oil was used to anesthetize live fish specimens after capture. Total length (TL) was measured for each sample to the nearest 1.0 mm. With a digital balance that was accurate to 0.01 g, we weighed the total body weight (W). Results: We collected four adult specimens of A. anguilla from the study area. Total lengths and body weights of the specimens were 311 mm and 62.4 g for Balıklıova Stream; 360 mm and 95.3 g for Küçükbahçe Stream; 325 mm 56.3 g for Salman Reservoir and 280 mm and 34.7 g for Yelkentaş Stream, respectively. Conclusion: We could not discuss our findings since no study has been done in the study area before, but it is thought that the low number of individuals caught may be related to the habitat degradation and different types of constructions at the stream mouths. The construction of fishways suitable for the study area can be a start to solving the distribution problem of this species.