SEATTLE - The city's Department of Planning and Development  is updating its Shoreline Master Program, a set of rules on Seattle's waterways.

The update could include a ban on new houseboat development to protect shorelines and salmon.

The state is directing the city to update the rules, which could affect one of Seattle's most iconic symbols.

"I'm concerned about salmon, too," says Amalia Walton of the Seattle Floating Homes Association, which commissioned its own study and found that salmon don't come near the shores and houseboats on Lake Union.

Houseboat advocates say their homes have little impact on salmon.

The new rules would also demote the houseboats' "preferential" water-use status to an "allowed" status. There are nearly 500 houseboats on Lake Union and Portage Bay.

The new rules will need City Council approval before going to the State Department of Ecology next year.