IRATE commercial fishermen and shop owners have joined forces to sue the Queensland Government for more than $20 million.

The group of about 60 people are seeking compensation for businesses losses associated with a diseased fish outbreak in Gladstone Harbour.

They're claiming the $70 billion port development at Gladstone Harbour contributed to the outbreak and impacted on their livelihoods.

Gladstone Harbour is being developed to make way for massive liquified natural gas and coal seam gas projects.