Some of the islands and rocks are listed below. Area is measured at
MHWS (figures are provided by the Isles of Scilly Wildlife Trust):
Daisy () in size. A haul-out site for grey seal.
Gilstone () The Gilstone (
Gilstone Reef or
Gilstone Rock, for an image see here) is also known as
Outer Gilstone Rock to distinguish it from a rock off
Old Town Bay on St Mary's which is also called
Gilstone. Gilstone has been the cause of many of the
shipwrecks recorded in the Isles of Scilly, most notably the sinking of
Admiral Sir Cloudesley Shovell's flagship in the
naval disaster of 1707 with the loss of over 1400 lives.
Gorregan () () in size. The smooth square fissured rocks of Gorregan ( high) is a contrast to the other islands which are a "disordered jumble" of rocks. The only plants recorded are common scurvygrass (
Cochlearia officinalis), rock sea-spurrey (
Spergularia rupicola) and orache (
Atriplex sp). The breeding colony of European storm petrel had 49 occupied sites recorded during the Seabird 2000 survey and there is a large colony of kittiwake, although in 1984 there was no breeding because of (possible) predation by carrion crow (
Corvus corone) or common raven (
Corvus corax). Other breeding birds are razorbill and guillemot. Grey seals use the island as a pupping site.
Great Crebawethan () () in size. The island was surveyed for European storm petrel during the Seabird 2000 survey with none found.
Hellweathers () () A group of rocks to the south of Annet.
Little Crebawethan () () in size.
Melledgan () () in size. Melledgan was the site of the third largest colony of European storm petrel in England with 140 occupied sites recorded during the Seabird 2000 survey declining to 69 occupied sites in a repeat survey in 2006 and being replaced by Roseveor. Cormorant and shag also breed on the island and it is a main pupping and haul-out site for grey seal. The seals' droppings enrich the shingle plant community. Plants recorded are tree mallow (
Lavatera arborea), spear-leaved orache (
Atriplex prostrata) and common scurvygrass. A rare
sea slug,
Babakina anadoni was found in UK waters for the first time in August 2022. In the eastern Atlantic, this sea slug has only been recorded a few times; off the west coast of Spain and further south on Atlantic coasts.
Retarrier Ledges () Lying between the Bishop Rock to the north-west and Rosevean to the south-east, their claim to fame is loss of 335 lives when the German liner
SS Schiller hit the rocks in 1875.
Rosevean () () in area and the highest of the Western Rocks with a maximum height of . Apart from the occasional plant Rosevean consists mainly of bare rocks and is important for its breeding birds and, as a haul-out site for grey seals. The island was surveyed for European storm petrel during the Seabird 2000 survey with 37 occupied sites recorded.
Rosevear () () in size. Rosevear is the largest of the Western Rocks, with a relatively flat top to . In 1709 and 1710 the island was used as a base camp for the Herbert salvage expedition, which worked the wrecks of the
Association and other vessels wrecked in 1707. In the 1840s and 1850s it was again inhabited by workmen, this time building the Bishop Rock lighthouse. The island has replaced Melledgan as the site of the third largest colony of European storm petrel in England, with 57 occupied sites recorded during the Seabird 2000 survey, increasing to 129 occupied sites in the repeat survey in 2006. The colony of shag on Rosevear and the rest of the Western Rocks is of national importance. ==Other named rocks and reefs==