(a) There shall not be used on any licensed boat any device operated otherwise than by hand power, for hoisting or operating dredges or other implements for gathering oysters, clams, mussels or other shellfish or oyster shells. Except as provided in subsection (b) of this section, no person shall use any dredge or other contrivance weighing more than thirty pounds, exclusive of the net or bag, or with a capacity of more than one and one-half bushels in taking up or dredging for oysters, clams, mussels or other shellfish or oyster shells in any of the waters of the state, except upon private designated grounds. Nothing in this section shall be construed to prevent the use of power in taking up or dredging for oysters, clams, mussels or other shellfish or shells on private designated grounds by the owners thereof, or to prevent the use of excavators for deepening the water in places where there are no natural oyster or clam beds, or where such beds have not existed within ten years, by digging or removing the material, permission to use excavators being first given by the Commissioner of Agriculture, which permission shall not be given until after a public notice of at least two weeks of the time when and place where he will hear all parties desiring to be heard upon such application, which notice shall be posted in the office of the town clerk of the town where such grounds are located.

(b) A local shellfish commission established pursuant to § 26-257a may allow limited and supervised use of a power dredge or other contrivance with a capacity of not more than three bushels, for the purpose of cultivation, enhancement or restoration of natural shellfish beds located within the jurisdiction of said commission. The use of a power dredge or other contrivance pursuant to this subsection shall not be extended to the harvesting or removal of oysters. Such shellfish commission shall administer such dredging pursuant to § 26-257a.