This thesis focuses on population dynamics and stock assessment like length weight relationship, growth, mortality, biological reference points (BRP) and maximum sustainable yield (MSY) of some important fish species of Nemipteridae and Synodontidae of Pakistan. Population dynamics study is the basic for better management for fish species. The study based on data collected during fishery resources survey during 2009–2010 covering five research surveys and catch and effort data of fish from the fisheries statistics book of Pakistan complied by Marine Fisheries Department (MFD), Karachi.　　Population dynamics of Nemipteridae spp. includes (Nemipterus japonicus and N. randalli) and Synodontidae spp. Includes (Saurida tumbil, S. undosquamis and Harpadon nehereus) Nemipterus japonicus.　　Japanese threadfin bream Nemipterus japonicus (Bloch, 1791) is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, demersal trawl surveys in October –November 2009 and May-June, August, October and November in 2010 were carried out. The purpose of this study is to estimate the population dynamics and status of the stock of the N. japonicus from Pakistani waters based on the research trawl surveys from the research area. The data consist of n=784 length-weight pairs and n=7530 length frequency with the maximum length and weight of 29 cm and 358 g respectively. The length frequency data were analyzed using ELEFAN method in FiSAT computer package. The parameters of length and weight relationship were b = 2.778, a = 0.032 and R2= 0.973. The estimated von Bertalanffy growth function parameters were L￥=30.45 cm, K=0.270 year-1 . Based on length-converted catch curve analysis the total mortality (Z) during this study was estimated at 0.960 year-1 The natural mortality coefficient (M) was 0.74 year-1 using Pauly’s equation (the annual average sea surface temperature was 27 C), therefore, the fishing mortality coefficients (F) were 0.22 year-1 . The yield per recruit analysis indicated that when was 2, Fmax was estimated at 1.2 and F0.1 at 1.1. When was 1, Fmax was estimated at 0.95 and F0.1 at 0.8. Because current age at first capture is about 1 year and Fcurrent was 0.22, Fcurrent is smaller than F0.1 and Fmax , which indicated that the fishery is about in a safe condition. When using Gulland (1971) biological reference point, was equals to M (0.74). The current fishing mortality rate of 0.22 year-1 was smaller than thetarget biological reference point, and fishing efforts can be increase, as long as the age-at-first capture is increased at the same time.　　Overall results of those demersal fish species shows that the stock of those fishes from Pakistani waters are in sustainable state but the fishery managers need to take some management steps to maintain the stock of these species from Pakistani waters for coming futures.