OSHKOSH, Wis. (AP) -- The shells of an invasive mollusk are piling up in staggering numbers around Lake Winnebago, choking off at least one small inlet and frustrating residents who say they can't get their boats through the channel.

The mollusk is the tiny zebra mussel. Its shell is only about the size of a fingernail, but enough shells have washed up to create a barrier several feet high.

An Oshkosh Northwestern report says the walls keep boats, fish and fresh water from passing between the channel and nearby Lake Winnebago.

Dave Ratajczak owns property along the channel. He says it's bad when you own a boat and you can't even get out.

A state wildlife official says there's no way to deal with the zebra mussels except to live with them.