Discovering spawning ground of Hilsa shad (Tenualosa ilisha) in the coastal waters of Bangladesh

The availability of suitable freshwater spawning habitat is considered to be a major factor limiting the natural recruitment of anadromous Hilsa shad (Tenualosa ilisha) in the coastal waters of Bangladesh. Against this context, we applied georeferenced habitat database to determine spawning habitat suitability index of Hilsa shad. Landsat imagery and thematic layers were analyzed with ENVI and GIS, and developed a series of GIS models to identify and ranking of suitable spawning grounds. Thus, among the studied 29,484 km2 aquatic ecosystems, only 6% (=1851 km2) area is the most suitable consisting of the rivers Meghna, Shahbazpur, Tetulia and Ander Manik as well as the channel of Sandwip island. Whereas, 20% (=5996 km2) area including river, estuary and near shore water bodies are moderately suitable, and in particular, the offshore deep waters occupying 73% (=21,637 km2) area is least suitable. The model outputs were verified after field data of fishers' indigenous knowledge with an accuracy level of 87%. This study suggests that necessary measures, such as conservation and management of spawning habitat should be implemented for an increased reproductive and recruitment success that will eventually improve populations of wild Hilsa shad in Bangladesh.