Serious city centre disturbance
Officers were called to Western Road at around 02.30 on Saturday when two groups of men were reported to be fighting in the street outside Buddha Nail Studio. It subsequently continued opposite McDonald's.
A man in his 30s was treated at the scene by the ambulance service and taken to hospital, where he remains in a serious condition.
Detective Inspector Ed Neve said: “An investigation is ongoing to understand the events of Saturday morning and identify any suspects.
“We are particularly keen to speak to the man pictured in white in the photograph.
If you have any information that could help the investigation, please contact Sussex Police online or via 101, quoting Operation Axle.