In the present study, the commercial (16 mm nominal mesh size) and experimental deep water cast nets with different mesh sizes (20 mm, 24 mm, 28 mm and 32 mm nominal mesh size) were tested to compare the captured fish lengths and catch amounts for whiting (Merlangius merlangus euxinus). Experiments were carried out between July, 11 and August, 29, 2018 in Rize province of the southeastern Black Sea Region. A commercial fishing boat was chartered for 20-day sea trials and in total, 66 set operations were done for all nets. Generalized Linear Mixed Models (GLMM) was used to compare fish sizes caught with experimental and commercial deep water cast nets. Results showed that more than 70 percent of the individuals caught in cast nets with 16 mm, 20 mm and 24 mm size were below the minimum landing size of whiting (13 cm). Among tested nets, only cast net with 32 mm size caught significantly less individuals under the minimum landing size. Finally, the results obtained from this study are discussed in terms of sustainable fisheries of whiting in the Black Sea.