The Gladstone Ports Corporation says dugongs have been sighted in the central Queensland city's harbour since a massive dredging program began.
A report on the environmental impacts of dredging has just been updated.
The environmental impacts briefing for the Western Basin Dredging Project says 12-million cubic metres of sediment has been dug out of the Gladstone Harbour since May last year.
The large-scale operation is almost half finished.
When completed, it will allow large liquefied natural gas (LNG) carriers to enter the port to export gas from Curtis Island.
The report says salinity levels have remained around average readings for the past month.
It says water quality appears to have improved and fluctuations in turbidity levels correlate with tidal conditions.
The report also points to several recent dugong sightings in the area, which it says shows they are feeding in the harbour.
It fails to mention more than 12 dugongs have also died in Gladstone since January last year.