Marine biological survey to establish the distribution and status of ...

The largest area was situated to the south of Sanday. The substratum appeared to be a
mixture of occasional boulders or small bedrock outcrops with some cobbles and shell on
burrowed mud or muddy fine sand. There were generally more species present on the
sediment surface than in the adjacent areas classified as burrowed mud
(SS.SMu.CFiMu.MegMax). Species present included the rugose squat lobster Munida
rugosa and edible crab Cancer pagurus with the burrowing anemones Cerianthus lloydii and
Sagartiogeton laceratus common. Pagurus prideaux with Adamsia carciniopados were
frequent and Pecten maximus, Neptunea antiqua, Echinus esculentus and Luidia ciliaris
were seen. The more unusual northern species of Luidia starfish, L. sarsi was seen at two
stations. Where there were boulders Caryophyllia smithii was invariably seen, Swiftia pallida
was sometimes present and there were axinellid sponges, particularly Axinella
infundibuliformis. Other species recorded included the bryozoan Porella compressa,
hydroids Nemertesia antennina and the white cluster anemone Parazoanthus anguicomus.
Species characteristic of the burrowed mud were also found such as the seapens Funiculina
quadrangularis and Pennatula phosphorea.
Plate 11
Screen grabs from drop-down video footage of Leptometra celtica aggregations
on mixed substrata in the Sound of Canna
3.2.7 Fan mussel aggregations
This MPA search feature has been assigned to the following provisional biotope for the
purposes of this report:
Aggregations of the fan mussel Atrina fragilis in poorly sorted mixed muddy
sediments
SS.SBR.SMus.Afrag
Distribution
Description
Depth range: 102 - 275 m
Total area: 170 ha
Fan mussels Atrina fragilis were recorded in the centre of the sound to the north-east of
Sanday (Figure 26). They were in deep water, with no mussels found shallower than 100 m.
The sediment was mostly very mixed muddy sand with cobbles, gravel, large amounts of
shell debris and occasional boulders. One station (A79) with dense A. fragilis, had rippled
sand with burrows. At some stations the shell debris consisted largely of Modiolus shells
suggesting that there may be or had been a horse mussel bed in the vicinity. The density of
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