The impacts of sanctuary on fish production and fish biodiversity were investigated in Dopi beel in Joanshahi haor over a period of two years from January 2004 to December 2005. Broadly two different types of materials were used to set two sanctuaries in Dopi beel referred to as Treatment 1 and Treatment 2; the control treatment was set in another beel named Chotadigha-boradigha beel without using any materials. Data on fish production and species abundance obtained from different treatments were compared. Ten major groups of fish viz carp, barb and minnow, catfish, featherback, snakehead, perch, eel, loach, miscellaneous fishes and prawn were obtained in the final harvest from different treatments. The fish species number was registered at 57, 60 and 62 in 2003 (before intervention), 2004 and 2005, respectively in Dopi beel, while that in Chotadigha-boradigha beel during the same period was 60, 55 and 50, respectively. The total production obtained from the Dopi beel was much higher than that from the Chotadigha-boradigha beel. The fish species deemed as threatened were found to reappear in Dopi beel, while in Chotadigha-boradigha beel the number of threatened species had been decreased over the 3-year period. The highest density index (H=0.89) and species richness (E=0.62) of threatened species were recorded in Treatment 1. Generally the yield of large species had been increased in Dopi beel during the investigation period. The establishment and management of sanctuaries in the beel had beneficial effects on the production of fish.