Tai Po fishermen blocked part of Tolo Harbour yesterday in a fight for $20 million compensation.
About 300 boats protested against plans to reclaim part of the harbour for a science park and luxury housing.
They prevented barges from transporting materials to fill the sea bed.
The fishermen said the reclamation had made the water so dirty they could not catch fish and demanded $1 million a year for the next 20 years.
They said they would mount the blockade again today and tomorrow. About 600 fishermen operate in Tolo Harbour.
The project, due for completion in 2000, aims to produce 60 hectares of land in the bay beside Chinese University.
A spokesman for the fishermen, Wong Yung-kun, said: 'After the reclamation, all the fish were killed and there are none for us to catch.' The Government has offered to pay $1 million a year for three years.
'That package is modelled on ones for people affected by dredging projects.
'After dredging, the sea is still there. But the sea disappears when land is reclaimed,' said Mr Wong.
A spokesman for the Planning, Environment and Lands Bureau said the compensation package was passed five years ago and the Government was unlikely to revise it.