The National Trust for Scotland (NTS) said it welcomed the ban on trawling and dredging around St Kilda.
The conservation charity which cares for the remote archipelago used World Heritage Day to highlight measures which mean that some fishing methods are no longer allowed in the area.
St Kilda celebrates its 30th anniversary as a World Heritage Site this year.
The international status is in recognition of their natural heritage, beauty and the significant natural habitats that it supports, notably the largest seabird colony in Europe.
This designation was extended to include the sea around St Kilda in 2004. There are only 47 marine World Heritage Sites in the world and this accolade puts it in the same category as the Galapagos Islands and the Great Barrier Reef.
St Kilda custodians welcomes trawling ban
18 April 2016
However, the Western Isles fishing fleet is hit by the ban. The local industry says the measures are excessive while reduction in catches means less supply for island processing factories, with the potential for job losses.
Comhairle nan Eilean Siar fears the islands are economically suffering for being "overly designated" and wants a ten year hold on introducing any new designations in the Western Isles, saying the number of environmental restrictions affecting the islands makes a significantly greater contribution than any other part of Scotland.
Dr Richard Luxmoore, senior nature advisor at NTS, said: “It is a great relief that as the 30th anniversary of St Kilda’s World Heritage status approaches, this new protection for the sea is finally in place, after years of campaigning.
“Although these waters have been a marine Special Area of Conservation since 2005, in practice, there was no legislation stopping harmful fishing methods.”
The use of set nets has also been prohibited -
Dr Luxmoore said: “Unfortunately these nets can also entangle other wildlife, notably seals and seabirds. And while we don’t know the scale of this issue, the decision to ban them is a welcome precaution that will benefit St Kilda’s million seabirds.”
Creel fishing for lobsters and crabs is allowed within the area.
Lying 41 miles west of Benbecula, St Kilda’s remaining population was evacuated to the mainland at their own request in 1930.