Mortality and yield parameters of the rose shrimp, Parapenaeus longirostris were compared with length frequency data collected from the beam trawl fishery in the Sea of Marmara. Von Bertalanffy parameters were estimated as L infinity=16.28 cm and K=0.490 year(-1). The rates of total (Z), natural (M), and fishing (F) mortalitiy were calculated as 2.83, 0.97, and 1.86 for a 32 mm PE (polyethylene) cod end. The Z and F rates for two other cod ends, 32 mm PA (polyamide) and 36 mm PA, were, respectively, 2.13 and 1.16, versus 1.57 and 0.60. A study on the relative yield per recruit shows that maximum yield can be obtained at an exploitation rate (E) of 0.53, 0.52, and 0.45, respectively, for 32 PE, 32 PA, and 36 PA cod ends, whereas the current E values are 0.65, 0.54, and 0.38. Consequently, 32 mm PE and PA cod ends cause overfishing pressure on the stock of P. longirostris.