Fluke Fairness Act of 2018 This bill directs the Mid-Atlantic Fishery Management Council to submit for approval by the Department of Commerce a modified fishery management plan for the commercial and recreational management of summer flounder, or an amendment to the plan, that: is based on the best scientific information available; reflects changes in the distribution, abundance, and location of summer flounder in establishing distribution of the commercial and recreational catch quotas; considers regional, coastwide, or other management measures that comply with national standards under the Magnuson-Stevens Fishery Conservation and Management Act; and prohibits the allocation of catch quotas on a state-by-state basis using historical landings data that does not reflect the status of the summer flounder stock, based on the most recent scientific information. Commerce must prepare and approve a plan if the council fails to submit the modifications or amendments. The Government Accountability Office must assess and report on whether the subsequent implementation of the approved plan or amendment complies with national standards.