Spatial distributions of common carnivorous planktonic chaetognatha Sagitta setosa, were studied between 7 - 13 July, 2001. Samples were taken from 150 meters depth to surface off Giresun, Trabzon, Rize and Hopa. CTD and nutrient were measured in situ. Nitrate, nitrite and phosphate values ranged between 0.377-1.284 mu g.l(-1), 0.001-0.155 mu g.l(-1) and 0.049-0.636 mu g.l(-1) respectively at the sampling station. In the laboratory studies, species were identified and lengths of the organisms were measured. The highest and lowest numbers of S. setosa were obtained from Hopa and Giresun stations, respectively. Average lengths of the organisms differed from region to region. Among the sampling stations, the highest mean length of the organism was obtained from Trabzon (8.99 mm) and the lowest obtained from Giresun (5.82 mm).