The hull for Australia's biggest rock lobster fishing boat left the workshop last week and is now in the final stages of assembly in Dongara, a small town on WA's Mid West coast.

The frame weighs 20 tonnes, stretches 24 metres and when completed in December, will hold 6.5 tonnes of live rock lobster, ready to supply an insatiable demand from China.

Dongara fisherman Clay Bass commissioned the $4 million vessel in 2017 and believes larger ships were the way of the future.

"You look back at farming, and you've seen over the past 20 to 30 years, what was a large number of farmers has become a smaller number," he said.

"I think that rationalisation is similar to what's happening in the lobster industry."

The number of operating rock lobster boats in Western Australia has more than halved since 2005, with 230 registered vessels currently operating in the fishery.

"With that fleet rationalisation down the entire coast, that has been at the detriment of some coastal businesses and communities," Mr Bass said.

"Having said that, obviously doing a new build like this is a massive boost."

A 20-tonne, 24-metre-long rock lobster boat hull ready to leave its Geraldton workshop for final assembly in Dongara. ( ABC Mid West and Wheatbelt: Donal Sheil )

Big boat, big impact

Dongara Marine managing director Rohan Warr was overseeing the second stage of the boat's construction.

The rock lobster industry contributed $16.3 million to Dongara's economy in 2016/17. ( ABC Mid West and Wheatbelt: Donal Sheil )

He said the increase in large-scale projects was fuelling a wave of employment in the town, stimulating the local economy, and delivering flow-on benefits to the community.

"I don't think people really understand the benefit of it; we are employing about 25 people down there," he said.

Mr Warr said increased capacity would allow fishermen to capitalise on high spot prices on the international market, where larger quantities of high-value product could be caught and processed more quickly.

The Western Rock Lobster industry contributed $16.3 million to Dongara's economy last financial year.

"It just all goes around; it's a huge injection which really does make a massive difference," he said.

A community divided

For tyre shop owner Malcolm Brogden the increased economic activity has not benefited all local businesses.

"The crayfish industry has the opportunity to have a flow-on effect within the larger community of Dongara business, but to date the flow-on-effect hasn't been that great," he said.

"There are industries that are specifically catered to the crayfish industry, and I'm sure that they would be picking up extra work.

"But for us, your hardwares, shopping centres, supermarkets, I'm not sure whether there has been any significant flow-on effect into those areas."

Mr Brogden said despite an employment boost, Dongara locals often left town to shop in neighbouring Geraldton, diverting money away from the local economy.

"There are a good number of people who travel outside of Dongara to do their shopping, which is a bit of shame because local businesses do their best to try and compete on price," he said.

"It makes it very difficult for the small businesses to survive."

Local business owner Malcolm Brogden says little flow-on effect can be seen throughout the community. ( ABC Mid West and Wheatbelt: Donal Sheil )

Waiting for change

While its new vessels were growing in scale and increasing yield, the broader economic benefits for Dongara were yet to fully form.

For large operators like Mr Bass, there was optimism that big boats such as his would stimulate the local economy long-term.

"It's really hard coming to a balance where communities are supported, and you have a viable operation. It's definitely not the easiest balance to get," he said.

"I do think that it's on the improve for the public and the fisheries."