Purpose and intended effect
The Scottish Government is committed to a clean, healthy, safe, productive and biologically diverse marine and coastal environment that meets the long term needs of people and nature. In order to meet this commitment our seas must be managed in a sustainable manner - balancing the competing demands on marine resources. Biological and geological diversity must be protected to ensure our future marine ecosystem is capable of providing the economic and social benefits it yields today.
The EU Wild Birds Directive (2009/147/EC as codified) requires Member States to classify as Special Protection Areas (SPAs) the most suitable territories for wild birds. Building on the work of the SPA Review Working Group and taking account of existing guidelines on the identification of SPAs (JNCC, 1999), Scottish Natural Heritage (SNH) and the Joint Nature Conservation Committee (JNCC) have identified 13 sites which they consider essential for marine SPA status. These proposals include sites supporting wintering waterfowl, important areas for red throated divers, terns, European shag and foraging seabirds.
The Sound of Gigha proposed Special Protection Area (SPA) is centred around the island of Gigha, which lies some 4 kilometres (km) off the west coast of the Kintyre peninsula in Argyll and Bute (Figure 1). The SPA covers a total area of 363.27km2 extending from Macrihanish Bay in the south to the entrance of Loch Caolisport off Knapdale to the North. It includes the sheltered waters of the Sound of Gigha between the island and the mainland and of West Loch Tarbert.
The area included within the SPA supports a population of European importance of the following Annex 1 species:
- Great northern diver (Gavia immer)
It also supports migratory populations of European importance of the following species:
- Common eider (Somateria mollissima)
- Red-breasted merganser (Mergus serrator)
This region of the western seaboard has a complex bathymetry due to a combination of the deepening of sea lochs and major channels by the scouring action of ice, which created locally-enclosed deeps with shallower seaward terminations ('sills'), and variation in resistance to erosion of the bedrocks. Consequently to the west of Islay the sea floor is generally flat and lies at a depth of between 40-80 metres (m), but to the east there are narrow, deep channels which separate the islands and continue benthic shape of the sea lochs seawards. Hence, in contrast to the Outer Hebrides and other islands further north, the waters close inshore to Gigha tend to be deeper (up to 50m) and rapidly deepen in places to over 100m. The SPA encompasses a band of relatively shallow water off the Kintyre coast.
The area also experiences a wide range of physical conditions, which in turn lead to a high diversity of habitats. West-facing open coasts, such as those off Macrihanish are fully exposed to the force of the Atlantic, while the sea lochs and sounds are protected from the prevailing winds and are for the most part sheltered from wave action. There are many rocks and skerries as well as small sheltered bays around Gigha and Gigha Sound is scoured by north-south channels. Offshore the sediments are a mixture of mud, sand and gravel while the very sheltered waters of West Loch Tarbert overlie soft mud sediment (Barne et al 1997). This complexity in physical conditions provides for a locally diverse range of habitats and associated fauna.
There is limited direct information on benthic habitats and species. Beds of seagrass, sea pens and gastropods are found in West Loch Tarbert while strong tidal streams at the entrance to Loch Caolisport overlie coarser sediments supporting burrowing species such as heart urchins and sea cucumbers. The presence of large numbers of eiders in the Sound of Gigha indicates the presence of beds of molluscs such as blue mussel.
Great northern divers and mergansers feed on a wide variety of fish that are associated with a range of seabed substrates. These birds catch fish by diving from the surface and pursuing their prey underwater. The fish species taken will be influenced by what is locally most readily available, but can include haddock Melanogrammus aeglefinus, cod Gadus morhua, herring Clupea harengus, sprats Sprattus sprattus and gurnard Eutrigla gurnardus along with smaller species such as sand-eels Ammodytidae, pipefish Syngathidae, gobies Gobiidae, flatfish Pleuronectidae and butterfish Pholis gunnellus. Great northern divers also feed opportunistically on small crustaceans.
Common eider feed almost exclusively on molluscs and small crustaceans, diving from the surface to pluck their prey from the seabed.
Great northern divers are capable of diving to considerable depths with figures of 60m recorded. Eider and red-breasted mergansers more typically feed at depths not exceeding 15m.
Eider are resident in this area throughout the year and red-breasted mergansers are typically short distance migrants, using coastal areas in winter. However, great northern divers are long distance migrants, moving annually between northern breeding grounds and more southerly wintering grounds such as those in the Sound of Gigha SPA.
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