Producers say work on a supply line has stirred up toxins and killed thousands of grouper Tai Po's offshore fish farmers yesterday demanded compensation from Towngas after alleging that work on a new underwater natural gas pipe has killed their fish. They and Democrat legislator Andrew Cheng Kar-foo met representatives from Towngas, the Environment Protection Department and the Agriculture, Fisheries and Conservation Department at one of the badly-hit farms to discuss their grievances. Law Kwong-choi, who breeds 80,000 to 100,000 green grouper and several thousand giant grouper at the farm, said he had already incurred losses of $80,000 to $100,000 since the start of the week. Mr Law did not say how many of his fish had died but he had no doubt who was responsible. 'As there are problems with the fish, Towngas should re-evaluate the impact of their works on water quality and the fish stock in the area,' he said. 'Do they realise that their works have wiped out my investment completely? They did not give me an answer and insisted it was a natural disaster. They are forcing us to become beggars.' Towngas is laying two 30km underwater gas pipelines from Cheng Tou Jiao gas terminal in Shenzhen to the gas supplier's plant in Tai Po. Work on the Hong Kong section began in July and is due to finish in December. The fish farmers said the work, which has just started in their patch, stirred up the sea bed and released a large quantity of sediment polluted with such toxic substances as heavy metals. The sediment and toxins clogged fishes' gills and suffocated them. The AFCD said initial tests on the dead fish were inconclusive and its vet had visited the fish farms again on Thursday to look for clues and take more samples. It hopes to release the results in the next few days. Senior Fisheries Officer Chow Wing-kuen said: 'Often such tests may not provide a clear conclusion because there are a lot of factors affecting fish health.' The EPD said its officers had followed the work closely to ensure Towngas implemented measures promised in its environmental impact assessment for the project. Senior environmental protection officer Ken Wong Yiu-kwong said regular monitoring of water and mud toxicity at the project site had found no abnormalities. The chairman of the Tai Po Yim Tin Tsai West Fish Farming Association, So Lau-sang, said more than 100 farms were affected and Towngas should compensate them and buy their remaining fish stocks. The gas supplier should also suspend pipeline work until a compensation package was agreed. Mr So said the farmers would move their farms to more open water today in a bid to save their stock. Towngas gas supply planning manager Sam Shum did not answer the fish farmers' demands directly but promised to hold further meetings with the group. Yvonne Sadovy, a marine biologist at the University of Hong Kong, would not speculate on the cause of the fish deaths in Tai Po until the test results were known.