Surveys of Ningaloo Marine Park and Exmouth Gulf in the winters of 1989 and 1994
recorded populations of about 1,000 dugongs on both occasions (though covering
slightly different areas). A subsequent survey in winter 1999 estimated the number
of dugongs in the region to be less than 350 – a population decline thought to be the
result of the destruction of seagrass beds caused by cyclone Vance in March 1999.