Junk or debris.
The rocks, crushed shells, and other sea detritus that create an oyster bed, where oyster spawn can attach themselves; a collection of such detritus, accumulated on land, to drop in the sea to build up oyster beds.
An accumulation of small items of little current value -- materials, broken items, miscellaneous fasteners -- for possible future use.
To prepare an oyster bed with such (culch) attachments; to sort shellfish or fish catch by size -- most often oysters -- so as to throw back the smallest to grow bigger and breed.
Location where potentially useful junk items are collected: culch corner, culch drawer, culch pile.
A bin for holding rubbish until it can be collected; a garbage can.