Kafr El-sheikh governorate is considered to be the first in fish production among all governorates in Egypt. it produces about 145.5 thousand ton or about 18.9% of the total fish production in Egypt in 2002/2003. Thus the main target of this study is to investigate factors affecting fish production in El-zawia fish farm, Kafr El-sheikh governorate. Series data as across sectional data for 54 observations during the period mentioned above were used and analyzed by multiple linear regression model, non-linear form as wall as the stepwise analysis. The fish varieties have been studied in the farm are: (i) Mullet and Ramada, (2) Tilapia. (3) Carp < /p> The most important results in according to economic statistical analysis of the linear and logarithmical functions are as the fallowing. The most important effective factors an fishery production are: Firstly: Mullet species: The important effective factors on the mullet and Ramada altogether are: The number Mullet-Ramada fingerling the number of the workers affects on the output of Mullet Ramada in the second yield stage. The production elasticities are about 0.04%, 0.06% respectively. But the output of tilapia affects inversely on the output of mullet Ramada altogether. The substitution elasticity is about 3.3%. _ ' ‘ ‘ Secondly: Tilapia species: _ g ‘ __ . The amount of forage affects an the production of tilapia in the second yield stage. The production elasticity is about 0.21% but the tilapia output affects on the output of mullet and Ramada in the same .direction. The substitution elasticity is about 0.85%. Thirdly: Carp species: _ fl The output of mullet—Ramada affects of the output of carp fish in the same direction. The“ marginal rate of substitution isqabout 020 ton. The results show that there is integration economic- statistical relation ship < /p> between them.