The Halda River is the one and the only natural carp breeding ground in Bangladesh from where fertilized carp fish's (Catla catla, Labeo rohita, Labeo calbasu and Cirrhinus mrigala) eggs are collected by local fisherman and egg collectors during April to June almost every year for time immemorial. The collected eggs are hatched in the artificial mud-made scoop on the riverbank to produce carp fries. The fry from here are supplied to different regions of the country for aquaculture.
Halda River is one of the major rivers in the South-East region of Bangladesh. It originates at the Batnatali Hill Ranges in Ramgarh Upazila under Khagrachari District (Former Chittagong Hill Tracts), Bangladesh. It flows through Fatikchhari Upazila, Hathazari Upazila, Raozan Upazila and Chittagong Chandgaon Thana before falling into the Karnaphuli River. The 98 km long river has a very turbulent tributary, the Dhurung River, which joins at Sundarpore about 48.25 km downstream. The river is navigable by big boats 29 km into it (up to Nazirhat) and by small boats 16-24 km further (up to Narayanhat). The Halda river is also famous for breeding pure Indian major carps. This is the only pure Indian major carp breeding field of Bangladesh, perhaps in South Asia.
Different man-made and natural disasters like destruction of spawning ground by ox-bow cutting, massive quarry of sands from river bed illegally by a section of unscrupulous traders, pollution of the river by industrial waste, unplanned construction of a good number of sluice gates by the locals for irrigation purpose, indiscriminate catching and killing of the brood fishes and climate change in the river have posed a serious threat to the bio-diversity of the Halda. Due to these risk factors, the river that was once a haven for brood fishes for releasing their eggs has now turned into a quite dangerous one resulting in drastic fall in the availability of eggs and fish-fries of natural species as lesser number of brood fishes have come here for releasing eggs in the recent years.