Carrying placards and banners, the fishermen marched to Cox's Bazar City from coastal villages days after the government's 65-day long fishing embargo came into effect.
"This is wrong. This is injustice. No other country in the world has ever imposed such a long ban," said union leader Kolim Ullah through a loudhailer during the protest.
Ullah said the ban has hit the livelihood of hundreds of thousands of people in Bangladesh's coastal districts, home to about 20 million people, most of whom depend either directly or indirectly on fishing, Presstv reported.
"The embargo has especially hit the poor fishermen hard. They don't know any other work," he said.
Bangladesh imposed the ban on fishing in the Bay of Bengal last week in an effort to replenish depleted stocks.
The junior minister for fisheries, Ashraf Ali Khan, said the ban would run from May 20 to July 23, and that navy and coast guard vessels would patrol the bay to prevent boats from putting to sea.
Bangladesh frequently slaps seasonal bans on fishing in deep seas and coastal rivers, but authorities said this was the longest-ever imposed for shallow waters near the coast. It covers all types of fishing boats.
Ullah said the protesters submitted a memorandum to the administrator in Cox's Bazar demanding that the ban be shortened to one month and the government stop foreign fishing vessels from entering Bangladeshi waters.
As part of compensation measures, the Bangladesh government has announced it will provide free rice for nearly half a million families of badly affected fishermen.
But S.M. Nazrul, another union leader, said the aid is promised only for the registered fishermen, while "the number of unregistered fishermen is eight times more than the registered ones."
Fishermen have also threatened to march toward the capital, Dhaka, if the embargo is not shortened.
"The ban is slapped on just before Eid," said fisherman Mohammad Rafique, referring to the largest Muslim festival of Eid al-Fitr. "How will we celebrate Eid when we don't have a penny in the pocket?"
The ban has also hit Rohingya refugees, nearly a million of whom have fled a military crackdown in Myanmar and found shelter in squalid camps near Bangladesh's Teknaf and Ukhia fishing towns.
The refugees are not permitted to work outside the camps but thousands have secretly found work in the sea-going fishing trawlers owned by Bangladeshis.
"Thousands of Rohingya work as crew members in a bid to find a better life. This ban would throw these Rohingya back on the streets," Abdus Salam, a boat owner in the Shamlapur fishing village, told AFP.
Every year Bangladesh imposes a weeks-long ban on the fishing of Hilsa — a popular Herring-like staple — and has created six sanctuaries in its network of coastal rivers to allow spawning.
The bans have boosted the Hilsa catch by more than 150 percent since 2004 and turned it into a $2-billion industry.