A three-mile strip from Skipsea to Spurn Point on the Holderness Coast, which has a “wealth of diversity” and shallow, rocky Runswick Bay, north-west of Whitby, are among those to have been designated nationally.
Yorkshire Wildlife Trust, which has campaigned for the new MCZs, said the historic move illustrated a “renewed impetus to protect the seas round our shores.”
The trust said the MCZs were “a tried and tested means of giving vulnerable species the time and space to recover from past damage and decline.”
North Sea Marine Advocacy Officer Bex Lynam added: “We welcome today’s designation of 23 Marine Conservation Zones.
“UK seas have the potential to be full of incredible life and colour but continued destruction has reduced them to a shadow of their former selves.
“Whilst many view the North Sea as a bleak, cold and lifeless the seafloor is in fact a rich tapestry of wonderful marine habitats from kelp forests and sandy plains to chalk reefs and deep rocky gullies.”
However an organisation representing fishermen, the Holderness Coast Fishing Group, said they were operating in an “environment of great uncertainty” because the kind of management measures they would involve have not been spelled out.
Trawling and dredging has long been banned from both areas.
The YWT urged the Government urged the Government to ensure the 50 MCZs announced so far were “properly managed”.
The Government has promised a third phase of MCZs.