The Present study deals with the ´´Zooplankton diversity of Lake Udai Sagar, Udaipur in relation to gut content of Catla catla (Ham.)´´. The outcome of the present study from planktonic diversity of Udai Sagar lake, a total 36 species of zooplankton was noticed. Out of 36 species of zooplankton, 18 belong to rotifer, 7 to cladocera, 7 to copepoda and 4 belonged to protozoa group from this lake. In the present study, the observed zooplankton ranking in order of: Rotifers Copepoda Cladocerans Protozoa Other. Qualitative and quantitative analysis of planktonic resources also revealed the moderate productivity of this lake. The average gross primary productivity (GPP) of Lake Udai Sagar was found to be 0.50 g Cm-3h-1. On the basis of average primary productivity, the fish production potential lake Udai Sagar was estimated to be 7533.6 Kg/ha/yr or 7910.280 Tons/yr (Odum,1971).Which showed considerable scope for the enhancement of present average production level 2365 Kg/ha/yr.