The Collaborative International Dictionary of English v.0.48:

Cultch \Cultch\ (k?lch; 224), n. [Etymol. uncertain.]
   Empty oyster shells and other substances laid down on oyster
   grounds to furnish points for the attachment of the spawn of
   the oyster. [Also written cutch.]
   [1913 Webster]

   2. Young or seed oysters together with the shells and other
      objects to which they are usually attached.
      [Webster 1913 Suppl.]

   3. Rubbish; d['e]bris; refuse.
      [Webster 1913 Suppl.]