A large extent of brackishwater resources is yet to be used for aquaculture as the present development stands at only 13% in India. But, growing environmental concerns and crop failures have made site selection a mandatory requirement for cage aquaculture. The case study carried out at Muttukadu Lagoon, India, has used 13 factors to assess cage site suitability, including physical characteristics and environmental conditions. Spatial analysis has integrated the most influencing variables such as depth, turbidity, salinity, temperature, dissolved oxygen, pH, and total ammonia nitrogen using suitability scores and its comparative rank. pH, salinity, temperature, and TAN were in the acceptable range throughout the year. Concerning depth, turbidity, and dissolved oxygen, 12–52%, 30–91%, and 84–91% of the lagoon were found to be suitable at different seasons. Overall, 11% of the lagoon region was found to be fit for cage aquaculture. Water depth was the major limiting factor in cage site selection. From the study, crucial management measures are outlined for successful fish culture and maintain the lagoon's health. This study will serve as a model to make use of the brackish-water regions to support the coastal population's livelihoods.

$\bf{Highlights}$

$\bullet$ Cage aquaculture can increase fish production and support the livelihoods of the coastal population

$\bullet$ Zero-footprint brackishwater lagoons and estuaries can be used for cage aquaculture

$\bullet$ Physical and environmental factors and their seasonal variations were incorporated in site selection using spatial analysis

$\bullet$ Identified sites can provide conducive environment for an entire farm cycle.

$\bullet$ Management measures are needed to preserve the conducive lagoon environment throughout the year.