By Sue Scott, Stromeferry
The minimum time it would take to extensively survey Loch Torridon would be about two weeks, and this was beyond the resources and remit of the Minch Project. Many of the larger sealochs have such a range of habitats that it would still be possible to find different places after a fortnight's diving. However it is possible to make subjective comments based on experience of diving many of the Scottish sealochs - so long as these are taken as such, and not based on detailed survey of the loch.
The loch is representative of north-western sealochs in general, but with its own special features. All sealochs have their own particular character, determined by their complexity, bottom topography, sediments, water movement etc. Loch Torridon (including inner and outer lochs and Loch Sheildaig) has a very good range of different habitats and some spectacular
places. It certainly has good tourist potential for diving and showing people marine life on the shores. For diving, the advantage of sealochs is in having sheltered sites for diving (and training) in good or bad weather, and for Torridon there is the added advantage of good diving outside the loch off Rona. It would certainly be easy to produce an attractive dive guide for Loch
Torridon and nearby areas, using the knowledge of local divers. A boat is needed for access to many sites. Divers also need appropriate accommodation (lots of room for gear, somewhere to hang and dry equipment) and preferably a source of air (compressor) to make an attractive package. Much more information on the needs of visiting divers could be provided, if this would be useful.
Urchins - at many bedrock sites the urchins have had a field day, but this is typical of outer sealoch situations, particularly in the north-west, and is not peculiar to Torridon. Its made easier for them because the glaciated rock slopes are very smooth, and easy for urchins to climb. Urchins have less effect where rocks are jagged and there are many overhangs or boulder sides. There may be scope for a sustainable harvest if it were small-scale and carefully monitored.
The sites below were visited for photographic purposes, and a brief description of the main characteristics and biota at each site is given. Some of the sites were previously surveyed by Smith (1985). Where possible, comments on the same sites from this survey are made. However no conclusions should be drawn from these regarding possible changes in the biota at the
sites, for several reasons. Firstly, this visit was primarily for photographic purposes, involving only 3 days diving, and there was not enough time for recording of biota in detail as well as good photography on the same dive.
Secondly, because marine communities and species can be very patchy, even within a few metres, any resurvey for comparative purposes would need to be done on exactly the same line. Thirdly, the sublittoral work on the original survey was carried out by "a team of very enthusiastic amateur divers with varying experience of marine survey work" (quoted from the report), and
results even within this team can be expected to vary widely. Lastly, the original survey was done in the first half of June, while this one was in November. Some seasonal seaweeds are likely to be gone by November, particularly those growing on pebbles and shells in mobile substrata.
In general, the Torridon loch system has a very wide variety of shore and underwater habitats, from exposed to extremely sheltered, and from rock through boulders and various grades of sediment to mud, at a variety of depths. There is a wide variety of communities and species in these different places, mostly typical of sealochs. Smith (1985) commented that life on
underwater rocks was much impoverished by urchin grazing, and this appears to be still the case. Sediments seem to be generally rich in both epifauna and infauna, perhaps as a result of little trawling in most areas of the lochs. A few particularly interesting animals and plants were found, including the green seaweed Codium adhaerens (both surveys), and the rarely recorded sea
cucumber Paraschistopus tremulus (this survey).
Depths have been corrected approximately to below chart datum.
Sron a' Mahais, N of Ardheslaig NG 783577. (Site 11/1 in Smith 1985)
This site is in the narrows between Outer Loch Torridon and Loch Shieldaig, and experiences some tidal stream movement. The seabed was a steep rock slope from the shore down to 30m and beyond. In the deeper parts the rock had a light scattering of coarse sand and shell gravel. At 28m, the deepest depth reached, the silty rocks had a few cup sponges (Axinella infundibuliformis), characteristic of deep water rock at the entrances to sealochs. There was also
a stalked sponge (Haliclona urceolus), and a few deepwater featherstars (Leptometra celtica) amongst the common featherstar Antedon bifida. The rocks had scattered small hydroids and many red cushion starfish (Porania pulvillus), but otherwise a generally barish appearance with a covering of encrusting coralline algae and barnacles, and scattered urchins Echinus esculentus.
Kelp Laminaria hyperborea grew down to around 10m, festooned with featherstars on stipes and fronds. Some kelp plants also had many seasquirts on the fronds, and a few snakelocks anemones. A few more animals were seen in shallow water - velvet crabs, shore crabs, spiny starfish, the prawn Pandalus montagui and dahlia anemones.
Sediments are mentioned at Site 11/1 in Smith 1985, including the goby Leseurigobius friesii which normally inhabits prawn burrows in mud, which suggests a different location from this one which was entirely of bedrock. She also has no records of the deepwater featherstar Leptometra celtica, but this species would probably have been recorded as Antedon bifida at that time.
Narrows between Upper Loch Torridon and Loch Shieldaig NG 814566. (Site 11/5 in Smith 1985)
Strong currents run through these narrows. North of Eilean a' Chaoil, the seabed at 9-11m was a plain of cobbles and pebbles, with some shells and gravel, and dense brittlestars Ophiocomina nigra. Towards the centre of the channel there was a covering of twiggy maerl (calcified seaweed, or 'coral'), also with dense brittlestars. There was a variety of other animals, including dahlia anemones, cushion stars, painted gobies, hermit crabs, swimming crabs, occasional edible crabs, and a sea scorpion (Myoxocephalus scorpius).
In deeper water at 13-24m to the east, the seabed was of increasingly large material; cobbles then boulders. These were covered with encrusting pink coralline algae, numerous keelworms (Pomatoceros triqueter), brittlestars, small hydroids (Obelia geniculata) and occasional grazing urchins. Dahlia anemones were frequent between boulders. Several rock cook wrasse were seen
beneath one boulder.
This site seemed substantially the same as the survey in 1985.
Between Shieldaig Island and Shieldaig NG 813540.
This site was visited to photograph a small eelgrass (Zostera marina) bed. The site was muddy sand at 1-3m, with the mud component increasing with depth. Patches of eelgrass at 1m had an interesting fauna, including many spider crabs Macropodia sp, a Connemara clingfish Lepadogaster candollei, and greater pipefish Syngnathus acus. The eelgrass blades had many didemnid (colonial seasquirt) colonies and hydroids growing on them, and populations of
small snails grazing on the surface. There were loose-lying algae amongst the eelgrass bases, and outside the eelgrass patches.
Sandy mud at 3-4m had a good infauna judging by the number of burrows and holes, some with radial scrape marks. The sediment surface had a layer of brown diatoms, and there were scattered razor shells. Scallops were frequent in the shallower parts, but are apparently someone's stash. Lugworm and terebellid worm mounds were also frequent, often with a hermit crab perched on
top. Most hermits had a covering of the hydroid Hydractinia echinata on their shells.
Sgeir a' Ghair, Outer Loch Torridon NG 725617. (Site 11/2 in Smith 1985)
This exposed offshore rock at the entrance to Loch Torridon was of fairly gently sloping rock to around 15m, then a gently sloping plain of maerl gravel waves with live maerl in furrows to 19m and beyond. There was a variety of animals in the maerl, including scallops (and spat about 1cm across), Connemara clingfish, seven-armed starfish, hermit crabs and swimming crabs.
The rock slopes were smooth with a crust of pink coralline algae grazed by urchins, and with a little silt cover in deeper parts. Dahlia anemones and featherstars were frequent. Above 9m, kelp plants were covered with featherstars, and fronds also had seasquirts and many small saddle oysters settled on them. In shallow, more wave surged water at 1-3m, kelp plants had long stipes, fairly bare in the lower parts but with featherstars above.
Beneath the kelp, rock surfaces were covered with encrusting coralline and brown algae, and scattered small jewel anemones Corynactis viridis, together with a few small edible crabs.
Smith (1985) mentions this site as the only one of the 1985 survey where jewel anemones were recorded (most exposed) - good populations of these are still present.
Sgeir na Trian, Outer Loch Torridon NG 732651. (Site 2/2 in Smith 1985)
An exposed rock in the centre of the entrance to Outer Loch Torridon, with underwater slopes of bedrock, broken in places by some sandy gullies, and ending in a sandy slope. The base of the rock on the north side was at 25m, with a short cliff to 20m, covered with masses of seaquirts Ciona intestinalis and patches of dense featherstars, with scattered red cushion stars, a patch
of orange plumose anemones Metridium senile and a few edible/brown crabs. This edge was subject to some current. A rope caught on rocks at the base was festooned with sponges. Above this, coralline-encrusted bedrock with urchins sloped at various angles, with the occasional dragonet Callyonymus lyra in the sandy patches. In shallower water kelp was dense, with long, barish stipes. Many featherstars were on the deeper kelp, and some big snakelocks anemones.
Several common seals came to join us at the end of the dive. A very scenic site.
S of Sgeir Ghlas, Red Point NG 732667.
The seabed was of coarse sand, shell gravel and shells, sloping gently up towards the rock from 13m to 5m. there was some current during the dive, and many specimens of the red seaweed Scinaia turgida suggests frequent currents.
Plenty of life, both on the surface and as infauna, judging by the number of shells lying around, including razor shells, big Arctica islandica and dog cockles. Sandeels and dragonet buried in the sand, a few scallops, swimming crabs, hermit crabs, decorator crab, common starfish, sunstars. More seaweeds above 7m. Joel Keating reports many skates and rays here in summer.
NW of Sgeirean Buidhe, Inner Loch Shieldaig NG 807534 (Site 4/1 in Smith 1985)
This site was dived specifically to photograph prawns, nephrops norvegicus. The sloping seabed at 22-27m was of sandy mud and mud. There were particularly good populations of the seapen Pennatula phosphorea, and many prawn burrows, some with prawns visible, including 1 juvenile (6cm). Also small gobies, which were presumably Leseurigobius friesii, known to live in burrows with the prawns. At 27m there were a few seapens Funiculina quadrangularis, the tallest
British seapen which can grow up to 1m high; these were about 60-70cm. At 22m there were some stones with squat lobsters Munida rugosa beneath.
This site sounds substantially the same as in 1985, when all three British seapen species were recorded. This time Virgularia mirabilis was not seen, but may well have been shallower than our dive. The goby Leseurigobius friesii was not recorded here in 1985, but was seen at other sites nearby.
W side of Shieldaig Island NG 809543 (Site 2/3 in Smith 1985)
This was a very sheltered site of steep and vertical bedrock and boulders to 14-17m, then scattered boulders and stones in a steepish muddy sand slope. At 19-23m, there were prawn burrows and a few seapens Pennatula phosphorea. The stones and boulders had a crust of pink coralline seaweed, and numerous large seasquirts Ascidia mentula attached. A few large urchins were on the boulders, and squat lobsters Munida rugosa beneath. Vertical rock at 14-9m had a similar pink coating, and was grazed by very big urchins. Here there were also some dense patches of seasquirts Ciona intestinalis, with a few red cushion stars, and two species of sunstar (Crossaster papposus and Solaster endeca). Crevices in the bedrock harboured small edible crabs, squat lobsters Galathea strigosa, rock cook wrasse, with leopard-spotted gobies Thorogobius ephippiatus on ledges. A deepwater sea cucumber, Paraschistopus tremulus, only recorded from
two other British locations in shallow water, both in Scottish sealochs, was also found here.
On less steep rock at 5m, kelp Laminaria saccharina grew, with rocks beneath grazed by very large urchins. The hermit crab Pagurus prideauxi wrapped in its cloak anemone was found here.
The sealoch anemone Protanthea simplex, which grows only in Scottish sealochs at very sheltered sites, was also recorded here in 1985, one of only 4 sites in loch Shieldaig and Upper Loch Torridon. The 1985 survey did not record leopard-spotted gobies at any sites, but these shy gobies are easy to miss.
S of Shieldaig Jetty NG 815535 (?Site 8/1 in Smith 1985)
A slope of muddy sand with shell gravel at 1m led down to mud at 11m, with prawn burrows, although no prawns were seen in them. A few tower shells Turritella communis were found at this level, and occasional burrowing anemones Cerianthus lloydii. Above 8m the seabed was covered with a mat of red filamentous seaweed ('Trailliella'), with a variety of animals living in it, including butterfish, hermit crabs, swimming crabs, velvet crabs, shore crabs, and topshells Gibbula magus. A few rock outcrops at 2-3m had kelp and urchins, with a few gobies, and colonial ascidians Botryllus schlosseri and painted topshells on the kelp stipes.
LITTORAL SITES
Ob Mheallaidh NG 832547 (Site 3 in Smith 1985)
Ob Mheallaidh is a wide bay on the south side of Upper loch Torridon with a shallow sill which almost cuts off a lagoon up to 7m deep at low water. This was the most interesting shore site surveyed by Smith (1985), and the brief visit to the north east corner of the bay for photographs indicates that this is still a rich site. Here, the sediments just inside the sill are coarse and
current swept, but very sheltered from waves, and obviously with a rich bivalve infauna, judging by the number of shells at the surface. Several small king scallops (Pecten maximus) were seen at low water this time.
Ob Gorm Mor NG 866546 and NG 864551
Ob Gorm Mor is an extremely sheltered bay on the south side of Upper Loch Torridon. The very sheltered arm at the southwest corner (NG 866546) had a freshwater stream running through, and was a typical sheltered sealoch inlet with rocky margins, with black lichens, mussels and egg wrack. Mud and sand in the bay had many lugworms Arenicola marina, and on the upper shore, beds of the unattached form of egg wrack Ascophyllum nodosum ecad mackaii, which develops from detached fragments of egg wrack, and grows into a very different much-branched, usually bladderless form in response to varying salinity in extreme shelter. This ecad is only found in Scottish sealochs, and the beds in Ob Gorm Mor are nice examples. The freshwater running through was also providing suitable conditions for mussels, which grew in abundance on boulders
and bedrock, presumably providing spat for the big mussel farm in the bay.
Winkle ('wilk') (Littorina littorea) pickers were at work on the east side of the bay.
At the top of this inlet, around high water springs level, was a good bed of moss wrack Fucus muscoides, a tiny brown seaweed which grows in amongst saltmarsh turf. This is also a sealoch speciality which develops in extreme shelter.
The small bay at NG 864551 was more a bit more exposed, with barnacles as well as mussels on bedrock and boulders, and clear zonation on steep rock on the exposed (north-facing) side. Inside the bay was more sheltered, with dense brown seaweeds on the mid and upper shore, and a dense patch of the unattached form of egg wrack Ascophyllum nodosum ecad mackaii.
Sgeir na Trian NG 732650 (Site 22 in Smith 1985)
This exposed rock in the centre of the entrance to Outer Loch Torridon has typical exposed shore communities. Of particular interest is the encrusting green seaweed Codium adhaerens which grows in large patches on the lower shore of the east side of the rock, and is at its northernmost recorded limit here. Otherwise the shores have typical exposed rock life, dominated in the midshore by barnacles, which had grown very crowded, tall and fragile on the east side
and were breaking off in places. There were many limpets and small mussels amongst the barnacles, and sponges and hydroids in crevices and overhangs. Some large shallow midshore pools had a crust of pink coralline seaweed, limpets and kelp. Urchins were grazing right up to low water, and there were around 10 common seals hauled out on the west side as we arrived. Shags roost on the top of the rock, which is consequently covered with guano and the green
seaweed Prasiola sp, typical of bird-enriched upper shore rocks.
The site appeared much as it did in 1985.
Diabaig NG 797598
This site at the end of the jetty road at Diabaig was smooth semi-exposed slopes of bedrock with gullies and fissures, and large rock pools. The shores were dominated by barnacles, with limpets, dogwhelks, common winkles and a few fucoid seaweeds. Winkles were even more abundant on the east side of the peninsula.
A full and comprehensive slide archive has been compiled and catalogued as part of this study and will be made available in support of the report and to the local communities. Initial steps have been taken to ensure that some of this material is used in local interpretive displays and
publications.
Smith, S.M. (1985). A survey of the shores and shallow sublittoral of Loch
Torridon and Loch Carron (including Loch Kishorn). Report to the Nature
Conservancy Council. NCC CSD Report No 610.
