AbstractWe quantified bycatch rates and determined selection criteria of landed narrow‐clawed crayfish (Pontastacus leptodactylus) in Turkey's most crucial crayfish production centres in 2020 and 2021. Subsamples (6078 individuals) of catches from 225 commercial fishermen were compared to 4836 crayfish landed without selection criteria during research fishing. Selection criteria used by traders for crayfish in commercial fishing purchasing centres included: (i) undersized; (ii) dead; (iii) soft shells; (iv) missing extremities; (v) lesions; and (vi) covered with moss. Based on the selection criteria, 77.2% ± 4.1 (95% confidence interval: 68.4–86.0) of the commercial catch were removed from the production chain as landed bycatch. The bycatch rate was higher than the global marine bycatch rate (40.4%). New studies are needed to improve fyke net selectivity, reduce the bycatch rate (40.7%) of undersized individuals, and determine the fate of bycatch.