Habitat point records from 1988 UMBSM Loch Ryan survey

Loch Ryan is situated at the southern entrance to the Firth of Clyde and is the most southerly of the Scottish sea lochs. It is 13.4 km in length and is shallow over its entire area with an average depth of 2 to 5 m. It is divided into 2 sections, a northern channel and a southern basin, by a shingle and sand spit which dries at low water. The southern basin experiences considerable temperature fluctuations including warming during the summer months. There is little freshwater input. The loch was seperated from Luce Bay, which lies to the south-east, by the deposition of raised beach material after the last glaciation; this formed the isthmus on which Stranraer now lies. The shores and subtidal in the loch are predominantly sedimentary in nature although there is sublittoral bedrock and boulder in the entrance area and littoral bedrock extends south to Jamieson's and Old House Points. The distribution of sediments is related to wave exposure and they grade from clean sands and gravel in the mouth to mixed sediments and mud in the sheltered central and very sheltered inner sections. Stranraer is the main centre of population in the area and ferries to Northern Ireland operate from Stranraer and Cairnryan. Angling is a popular sport and there is some associated bait digging for lugworms. A major feature of interest in the loch is the presence of large beds of native oysters Ostrea edulis in the southern basin which have been fished since prehistoric times. Despite overfishing around the turn of the century, a fishery still exists and efforts are being made to improve the commercial viability of the beds. There is little other commercial fishing in the loch which is a static gear reserve. However cockles are collected from shores on The Spit and the head of the loch using hydraulic pumps. There are no terrestrial sites of conservation interest bordering the loch which has been proposed as a Marine Conservation Area on the basis of the present survey. Scientific interest in the past has been concentrated on the structure of the oyster population with a limited amount of flora and fauna collecting and recording by other workers. Annual monitoring of the infaunal communities is carried out around the creamery outfall at the head of the loch although the results of this work have not been made available for this report. The present survey, carried out in September 1988, aimed to describe the marine habitats and communities present in the loch and to assess their nature conservation importance. A total of 20 sites were visited of which 6 were intertidal and 14 were subtidal. The latter were surveyed by diving. At each site the abundance of the epiflora and fauna was recorded and the habitats were described. No infaunal sampling was carried out. Descriptions are given in this report of the 14 intertidal and nine subtidal habitats and communities considered during the survey. A list of taxa recorded is given. Communities in the entrance of the loch are open coast in nature and not very diverse. A bed of Zostera marina was found in this area. In the central loch, communities indicative of unstable substrata and some tidal movement are present. The inner loch contains a bed of Ostrea edulis and a luurient growth of the seaweed Spyridia filamentosa. Shingle and muddy sand on The Spit support rich intertidal communities including several species normally considered sublittoral. Beds of Zostera noltii and Mytillus edulis were found at the head of the loch. The scientific interest and conservation importance of the area has been assessed using standard criteria. These have been applied to each of the habitat or community types identified which have been provisionally graded as of Local, Regional, National or International importance. Species of particular scientific and conservation interest have been tabulated and their provisional conservation importance graded as Regional or National. Loch Ryan is unusual amongst the Scottish sea lochs and has affinities with inlets further south in the British Isles. The oyster beds appear to be the only remaining extensive beds in Scotland and are considered of National importance. The full conservation significance of communities in the loch will only be adequately assessed when surveys of other Scottish lochs are complete. Records currently considered sensitive have been removed from this dataset.

Organization: Joint Nature Conservation Committee