Domestic Commerce Improvement Act

Domestic Commerce Improvement Act - Amends the Merchant Marine Act, 1920 to prohibit vessels which are entitled to engage in coastwise trade and subsequently have major work done (currently, are rebuilt) from engaging in coastwise trade unless all the major work is effected within the United States. Amends Federal law to condition a fishery license or registry on all major work (currently, any rebuilding) having been done in the United States. Conditions a fishery license to engage in fishing near Guam, American Samoa, and the Northern Mariana Islands on all major work (currently, building or rebuilding) having been done in the United States.

Allows, notwithstanding other specified Acts, a coastwise endorsement for a vessel that meets certain requirements, including that it be owned by a corporation qualifying as a citizen of the United States. Limits the activities of a vessel documented under these provisions, or chartered to a corporation eligible to document a vessel under these provisions.

Amends the Shipping Act, 1916 to apply provisions prohibiting the transfer of a vessel to a non-U.S. citizen to vessels documented under provisions of this Act, but excludes from that application the charter of a vessel to a person eligible to document a vessel under provisions of this Act.

Repeals provisions of the Merchant Marine Act, 1920 relating to corporations as citizens, fisheries and transportation of merchandise or passengers between U.S. points, parent and subsidiary corporations, domestic-built vessels, certificates, and surrender of documents on a change in status.

Amends Federal law to prohibit, subject to exception, a dredge, under penalty of forfeiture, from dredging in U.S. navigable waters or the Exclusive Economic Zone unless the dredge is built in and documented as a vessel of the United States and its owner or operator meets the citizenship requirements for documenting vessels in the coastwise trade.

Amends the Merchant Marine Act, 1920 to include merchandise owned by the United States or by any State in provisions prohibiting the transportation of merchandise between U.S. points in other than domestic-built or rebuilt and documented vessels.

Authorizes the Secretary of the department in which the Coast Guard is operating to issue a coastwise certificate to a vessel engaged in dredging which meets certain requirements. Requires the certificate to be endorsed to prohibit the vessel from transporting merchandise (other than valueless material), including dredged materials of value, between U.S. points.