Pieter Claesz, 1645
Oysters were common in the waters surrounding Manhattan and were an important source of food for the settlers. An oyster is a bi-valve mollusc that lives in brackish waters like those at the mouth of the Hudson and surrounding Manhattan Island.
Native Americans had been eating large quantities of oysters for many years, and they left enormous piles of oyster shells called 'middens' by archaeologists. Some shell middens are more than 4 feet deep.
"The early 17th Century Dutch were the first to notice the shell middens. One such mountain of oyster shells gave Pearl Street, originally on the waterfront in lower Manhattan, its name." The Big Oyster, Mark Kurlansky, p. 12.
See The Big Oyster by Mark Kurlansky for more information:
http://www.amazon.com/Big-Oyster-History-Half-Shell/dp/0345476387
Oyster shells were available to the Dutch in such abundance, that they ground them and created a beautiful pearlescent finish for the walls of their homes.
http://en.wikipedia.org/wiki/Oyster
See link to original Dutch Documents collection regarding digging Oyster shells: