Mother fish release unfertilised eggs in Halda, rain needed for full spawning

Egg collectors in Chattogram's Halda River are waiting for upstream rainfall to trigger peak breeding, as full spawning has yet to begin two days after carp mother fish released sample eggs or unfertilised roe amid unfavourable conditions.

The sample eggs were found early 27 May during high tide in three locations of the river – Noyahat in Garduara union of Hathazari, Azim Ghat in Paschim Gujra of Rauzan, and Katakhali near Napiter Ghat. Egg collectors reported finding 10 to 15 eggs each.

Every year, between 700 and 800 egg collectors prepare along the riverbanks to collect fertilised eggs during the spawning season.

However, with the declining volume of egg release in recent years, their numbers are also believed to have dropped.

Professor Md Manjurul Kibria, coordinator of the Halda River Research Laboratory at the University of Chittagong, said, "Normally, during the dry season, the river suffers from pollution. Heavy rain on Tuesday has helped clear it, and temperatures have now dropped to between 27°C and 32°C."

"The water quality has improved. However, there has not yet been any rainfall upstream."

He added, "The turbidity of the river is currently between 100 and 150. For full egg release, turbidity needs to be between 600 and 700. We are now waiting for rainfall upstream, which is likely between 23 and 29 May."

Professor Kibria also said that 700 to 800 egg collectors, equipped with 300 to 350 dinghies, are ready to begin collection once full spawning starts.

Egg collectors and officials say this is the fourth new moon tide of the season, which is expected to continue until 29 May. If favourable conditions are not met, the fish may spawn during the next full moon tide from 8 to 14 June.

Hathazari Upazila Nirbahi Officer (UNO) ABM Mashiuzzaman told The Business Standard, "A small quantity of eggs has been released. The upazila administration and the fisheries office have taken all necessary preparations. Everyone is now waiting for upstream rain, including in Khagrachari."

According to fisheries researchers, climate change has led to record-high temperatures and increased salinity this year. These conditions have stressed the river's carp-like fish, which typically wait for rain, thunder, and hill torrents before releasing eggs in large quantities.