NatureScot Research Report 1155 - Monitoring for the possible spread of Didemnum vexillum into the subtidal environment of Loch Creran

The Loch Creran SAC was established to afford protection for the marine feature reefs, which includes the biogenic sub-features serpulid reefs and horse mussel beds, as well as the bedrock reefs of the loch.  Loch Creran is also designated as a Marine Protected Area (MPA), conferred to protect the flame shell beds and geodiversity features. Loch Creran contains the only example of well-developed serpulid reefs in the MPA network. 

The invasive colonial sea squirt Didemnum vexillum was first recorded on an oyster farm in Loch Creran in 2016.  In view of its possible spread into the subtidal environment, the current study established a diving programme to monitor such spread, with particular emphasis on colonisation of the protected features, serpulid reefs, horse mussel beds and flame shell beds.

The approach taken involved a combination of repeated surveys of the habitat along fixed, relocatable transects, and of artificial structures, such as pontoons and moorings.  

In addition, more extensive coverage of the loch was achieved through assessment of the presence of D. vexillum as part of a site condition monitoring survey of the SAC and MPA protected features of the loch which accompanied this contract, and which will be reported on separately. It determined the condition of the reefs feature to be 'Unfavourable Declining'. 
 

Pages: 29
Published: 2020

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