�At a guesstimate, less than 25 per cent,� Dr Hames said.
Dr Hames said he emphasised the Government wanted as many berths as possible for public and daily boaters� use, when he opened a $240,000 seal viewing platform at the island�s west end last Friday.
�I absolutely don�t want them (developers) to sell off a large portion of berths, as they should be priority use by day trippers,� he said.
Two days earlier, the Government called for expressions of interest for a marina for large to small boats next to 100-150 units and to supply barge facilities at the south end of the island�s main Thomson Bay.
Fremantle MLA Simone McGurk, whose electorate includes Rottnest Island, said there was a risk a marina builder could say berths had to be sold or made exclusive for project viability.
�Will they be going to be used by large craft, and people with money, and not for public access?� Ms McGurk said.
The seal viewing platform marks half- way in construction of the island�s 50km Wadjemup walk trail, costing $8.5 million to date, to which BHP-Billiton contributed $532,800 for future work on bush restoration, trail building and signs by volunteers, including the Rottnest Foundation.
�We never thought it would get this far, after foundation founder Des Sullivan, who was island manager from 1960, said it was one of his dreams that there would be a complete network of walks around the island,� Foundation co-founder and Claremont resident Pat Barblett (83) said.
Thornlie Noongar woman Janet Hayden, who greeted Dr Hames and Ms Barblett to the island, said the trail reflected traditional paths used on the mainland before colonisation, but more work was needed on the island�s use as an Aboriginal prison and cemetery.
�When our youngsters come over here and do a Welcome to Country, there seems to be a peace and no anger anymore,� Ms Hayden said.