Deep water cast net fishing is regarded as a traditional method that has been used since antiquity in the Eastern part of the Black Sea. Unlike ordinary cast nets, it is used in deep waters from shallow up to 140 meters for catching whiting (Merlangius merlangus euxinus). In this study, important findings were obtained about the operational success and duration, catch efficiency and composition of traditional deep water cast nets. The highest operation success rate was obtained from 60 to 120 meter depth with 84.2%. The highest mean CPUE was established at 0.42 kg/operation in August. The catch rate of whiting, the main target species of the study, of the total catch was calculated as 98.8%. In this study, the effect of deep water cast nets on the ecosystem was also investigated. According to the findings, fishing season and operation depth significantly affect the catch per unit effort. In terms of ecosystem-based fisheries management due to high selectivity, the low impact of ghost fishing and high survival rate of the individuals, the deep water cast net fishing was found to be beneficial. It is recommended that the performance of deep water cast nets on different species in different seas should be investigated.