Dolphins are still not safe in the marine protected swatch of no-ground areas of the Bay of Bengal and the Sundarbans' dolphin sanctuaries, according to a wildlife expert.

"Fishermen have been catching fish in the marine protected swatch of no-ground areas through the unplanned use of nets, while ocean-going ships are running through the areas, putting dolphins at risk," senior researcher of US-based Wildlife Conservation Society (WCS) Jahangir Alam told the news agency.

He said some 130 dolphins were killed in the areas from January 2007 to April 12, 2016 after being trapped in fishing nets or ship propellers.

According to the Forest Department officials, at least five species of dolphins and several species of whales are found in the dolphin habitat located in the 1,738 square kilometre swatch of no-ground areas of the Bay. The government declared it as a marine protected area in 2014.

Jahangir Alam, also coordinator of Bangladesh Cetacean Diversity Project (BCDP), said although the government announced three areas of the Sundarbans as dolphin sanctuaries three years ago, dolphins were not safe there.

He said the authorities concerned were yet to implement the management plan that they prepared to protect dolphins in the rivers of the mangrove forest.

In 2012, the Forest Department declared three areas of the rivers and canals in the Sundarbans covering 32km as dolphin sanctuaries.

Around 12km from Ghagmari check-post of Chandpai Range to Karamjal check-post through Dhangmari canal and Pashur River, 15km from Jongra check-post to Andharmari check-post through Mrigamari check-post and 5km from Dudhkhali check-post to Supati canal through Bemara canal were declared safe havens for dolphins.

Dolphins move around mostly in the rivers of Dhangmari, Chandpai, Andharmanik, Dudhmukhi, Betmore and Patakata of the Sundarbans East Zone under Khulna and Bagerhat districts, said Jahangir.

A joint survey conducted by WCS and BCDP in 2010 revealed that there were 225 Gangetic river dolphins, 6,000 Irrawady dolphins, over 1,000 bottlenose dolphins, about 1,400 finless porpoises, and a significant number of Indo-Pacific hump-backed dolphins, pan-tropical spotted dolphins and spinner dolphins in the Sundarbans and adjacent water bodies and the swatch of no-ground areas.

Dolphins are also found in the Brahmaputra, Jamuna, Meghna, Karnaphuli, and Sangu rivers.

Divisional Forest Officer (Sundarbans East Zone) Md Saidul Islam said fishermen were not allowed to fish using nets in the dolphin sanctuaries of the Sundarbans; the Forest Department took legal action against those found fishing there.