Following the WMN’s in-depth look at contentious plans for Falmouth Harbour, local fishermen have been telling Martin Hesp about their concerns.

Fishermen in Cornwall have declared they will fight plans which they claim could see more than one million tonnes of waste material dumped on one of their best fishing grounds.

In the past few days more than 25 local skippers have signed a document which objects on several different levels to the proposed dredging of Falmouth Harbour.

As reported in the Western Morning News on Monday, Falmouth Harbour Commissioners have been spearheading plans to deepen approaches to the port so that large ships including cruise liners can enter the docks. But local fishermen say materials removed from the estuary bed will be dumped out at sea in an area which they rely on for their livelihoods.

They are also worried that toxic substances, known to lie dormant in the estuary bed, will escape in a cloud of silt while the dredge is underway, polluting rich fishing areas including the famous Fal oyster grounds.

"The situation is complicated," said local fisherman David Thomas. "We fishermen haven't had much of a say but the harbour people have played a blinder – they've even got the Chancellor mentioning their plans in the House of Commons."

He said local skippers already knew to their cost that the dumping of dredged material in an area a few miles off the coast – marked as "spoil ground" on the charts – harmed the fishery.

"It's been calculated that 1.1 million tonnes of material will be dredged and we know that in the last 24 years 230,000 tonnes have been deposited on that spoil ground from maintenance dredging in the harbour and up the Truro River," said Mr Thomas. "That averages 10,000 tonnes a year – but the biggest lot was when they dredged Mylor Yacht Harbour in 2001 and they put 47,000 tonnes out there.

"I started prawn fishing in 1999 and was able to buy plenty of local mackerel for bait, but in 2001 we couldn't get any because mackerel didn't come in that summer and autumn. The 47,000 tonnes absolutely destroyed the summer/autumn mackerel and whiting fishing for years," said Mr Thomas, adding that the area in question was close to a wrecked Second World War "liberty ship" which was a favourite target for fishermen.

"It's only in the last three years that whiting have been caught in any quantities in the bay and it was the summer before last that the mackerel came back like they used to be 12 years ago," he added.

"If 47,000 tonnes can do that, what will over one million tonnes do?

"By their own admission, the Harbour Commission's own consultants say the liberty ship will be buried by four inches of silt. We will never catch any fish there ever again."

Mr Thomas, who has a degree in applied biology, said he had attended meetings where various issues regarding the dredge material had been discussed. Suggestions included that it should be taken to an area within the harbour and used to create a land-fill in which toxic substances could be safely sealed in concrete.

"It was never progressed because Natural England said it would be a loss of natural habitat," he added.

"But even if the hard standing idea went ahead – there are two groups of local fishermen here – there's the ones like me who go out to sea and then there's the people in the Carrick Roads. Those fishermen are very worried about the dredging stirring up the sediments which include things like TBT (an anti-foul chemical now banned). In total it's reckoned around 6,200 tonnes of sediment will be released into the water column while the dredging is going on – then that stuff is going to get deposited somewhere – it could end up all over the oyster beds."

Mr Thomas said that the monitoring buoys which the proposed scheme would employ to measure toxins were simply not up to the job.

Among those joining the fight against the big dredge is fishing industry journalist Phil Lockley who also fishes commercially in the area. "I'm not against the dredging," he said. "We want the ships and we want the industry – but we are worried about where they are going to dump all that material.

"That area is my living. I cannot emphasise enough how vital that area is for local boats."