In this study, the socio-economic structures of Karasu (Sakarya) marine fishermen are investigated. Between July 2004 and July 2005, there were four visits to the Karasu Region to make interviews with fishermen. There are 143 fisherman vessels in which are registered to Sakarya Agriculture Province Directorate. 36 fisherman vessels have trawl and purse-seiners licence, also 107 vessels have less than 11.00 m other class licence. Fishermen's age distribution, education status, marital status, their spouse's education and work status, their children's education status, fishing period, total numbers of fishing days, fishing zone distances to the port, caught aquatic products species, features of fisherman vessel's and fishing gears are investigated. Fisherman vessel's length are maximum 22.00 m and minimum 6.50 m, vessel ages are maximum 45 years and minimum 2 years, fishing periods are maximum 240 days, and minimum 30 days; mostly fishing of aquatic products species are Atlantic bonito, bluefish, whiting, turbot, Atlantic horse mackerel, grey mullet, Mediterranean shad, red mullet, striped red mullet, shark, ray, clam and sea snail are determined.