Four types of shrimp trawl nets 4, 5, 7.5 and 10 mm mesh sizes were used to assess the efficiency of various shrimp trawl nets modification to select and reduce the catch. The catches were affected by different meshes. After five months (Fifteen fishing trips) average catches was calculated per mesh size as follows: 11.11, 10.83, 7 and 6.24 kg for 4, 5, 7.5 and 10 mm, respectively. Average weights of targeted and non-targeted catches were calculated as follows: 1.39, 1.64, 1.4 and 1.31 kg and 9.72, 9.19, 5.6 and 4.93 kg for the same models, respectively. Discarded fish were reducing significantly (P≤0.5) with increasing of mesh sizes, where increasing mesh size up to 7.5 and10 mm in a trawl end was limited for discards and shrimp No.3. Results indicate that substantial improvement in size-fish for shrimp is achieved by switching from the conventional 4 mm-mesh sizes to a 10 mm-mesh size. The minimum mesh size of the shrimp trawl especially used in shrimp fishery must be 7.5 mm in order to protect fish stocks and optimum catch efficiency for the future. On the economic level, the study showed that the use of 7.5 mm as a mesh size will slightly decrease the total income on a short term but will protect fish stock and secure a profitable on long term. Hence, there is a need to identify the potential long and short-term benefits by lagoon management.