In this study, freshwater crab (Potamon potamios, Olivier 1804), economically unevaluated, was used to obtain chitin-chitosan. Chitin-chitosan was extracted with standardized modified chemical method. Chitosan was extracted with demineralization, deproteinization, decoloration (chitin) and deacetylation (chitosan). Grinded shell was obtained as 60% after boiling, drying and grinding processes. Chitosan yield of crab shell was determined as 4.65% from grinded crab shell after demineralization (yield is 34.32%), deproteinization (yield is 7.25%), decoloration (yield is 6.83%) and deacetylation processes. Moreover, freshwater crab stock was estimated with catch per unit effort (CPUE) data in Eğirdir Lake for calculation of quantity of chitosan. Population size was estimated between 12.85±11.88 and 23.86±25.39 tones and freshwater crab was determined as an appropriate crustacean to obtain chitin-chitosan.

Key words: Chitin-chitosan yield, CPUE, Freshwater crab, Population size, Potamon potamios