THOSE against the development of an outer harbour off Kwinana will take their fight to a local council meeting tonight.

Fish Army convener Tim Barlow said recreational anglers, Naval Base shack owners and union groups would gather outside the City of Cockburn’s administration in Spearwood at 6pm to demonstrate their opposition to the project.

They also plan to use public question time to query the basis for the City’s support of the project.

While a number of councils, including Cockburn, Fremantle, East Fremantle and Kwinana have previously supported the outer harbour in Cockburn Sound, Mr Barlow said the group was sparked into action by an item up for discussion at tonight’s meeting.

A recommendation being considered is for councillors to adopt a corporate business plan which includes participating “in the campaign and advocacy for an outer harbour”.

Mr Barlow said there would be no need for the project for decades, arguing Fremantle Port was operating well below capacity and dredging in the Sound would destroy seagrass.

“The rally out the front will be a show of force, to show there is a strong voice against this,” he said.

“There’s no scientific basis for this, no mention of the snapper, squid, mulloway or crabs in this critical spawning area.”

Mr Barlow said further rallies at other councils could happen.

“We’ve got lots of love to share,” he said.

City of Cockburn chief executive Stephen Cain said there was little issue with the gathering.

“The City welcomes residents to attend and observe any of its meetings, with the expectation that they do so in an orderly manner,” he said.

Mr Cain said the local government began advocating for an outer harbour in 2015.

In September last year Planning Minister Rita Saffioti announced the Westport Taskforce had been established to complete planning for the State Government's long-term “Outer Harbour freight vision”.

“The future outer harbour is a vital piece of economic infrastructure that presents an opportunity to increase local jobs across various industries,” she said at the time.

While the outer harbour has been seen in some quarters as part of an alternative to the failed Perth Freight Link project, Mr Barlow said he did not have an opinion on the road.

“This isn’t about Roe 8 from my point of view,” the Guildford tackle shop owner said.