In this study, age, sex compositions, mortality, age-length, age-weight, length-weight relations, condition factors monkey goby, Neogobius fluviatilis (PALLAS, 1814), were determined from 622 specimens between April 2006 and March 2007 caught in Manyas Lake, in the Northwest of Turkey. The age compositions of specimens were between 1-5 years and sex percentages were found as 41.64% for females and 58.36% for males. The total length varied between 5.80 and 15.60 cm and the weight ranged from 3.80 to 47.20 g. Growth of population was the most rapid at the first year of life afterwards growth ratio was slower. Growth were expressed in length and weight and the von Bertalanffy growth equations were found as, Lt = 22.89 (1-exp(-0.489(t + 1.390))) and Wt = 99.85 (1-exp(-0.489(t + 1.390)))(2.9848) The following equation is for length-weight relationship, W = 0.127 TL(2.9848), R(2) = 0.8763. Weight increased allometrically for all sexes as seen b = 2.9848. It was determined that the average condition factors of ages are changed between 1.192 and 1.283 for females and 1.225 and 1.458 for males. The population has shown better growth performance than others habitats because of the lake low latitude. We have given the population parameters and characters from Northwestern part of Anatolia in Manyas Lake.