Two people sustained injuries after a gang disorder outside The Thirsty Whale Bar and Restaurant in the early hours of Sunday morning.
Police were called to the West Quay address about 3.35am following a report of disorder.
A police spokeswoman said two people were injured during the incident.
"It does not appear the injuries were serious," she said.
A witness, who wished to remain anonymous, said a Thirsty Whale security guard was stabbed in the hand by a member of the Mongrel Mob during the affray.
"One of the bouncers was punched by a member of the Mongrel Mob. Then another bouncer ran into the fight and that's when he got stabbed," she said.
"More security got involved and pinned someone down. It was a big fight."
However, The Thirsty Whale owner Chris Sullivan denied his staff were involved in the incident.
"There was a small incident by the fuel pump on the wharf," he said. "Three gang members were involved, but there was no fight."
Sullivan said no bouncers were involved, as only cleaning staff remained at the bar.
"Police were called and arrived quickly, but the mob members scurried into the dark," he said.
"The bouncers finished at 3.30am and most had gone home. There was a rumour of a knife, but when police questioned people in the area, nobody saw it."
Police are continuing to make inquiries.