The Sarnau of Cardigan Bay
The Three Sarnau of Cardigan Bay
Reproduced from Admiralty chart 1972 Cardigan Bay Central part
By permission of the controller of her Majesty’s stationery Office and the UK Hydrographical Office
(www.ukho.gov.uk). Not to be used for navigation.
For our pilot surveys we focused on the two most southern Sarnau, Sarn Cynfelin and Sarn-y-Bwlch.
Sarn Cynfelin starts from below the farmhouse at Wallog situated on the cliffs between Borth and Clarach near Aberystwyth and extends some 14 kilometres offshore and is bisected by a 5 metres deep channel approximately half way along its length. Charted depths as shallow as 1.5 metres have been recorded, both near the mid-channel and, also, near to its western prong or outermost extremities to seaward.
Photograph below showing Sarn Cynfelin looking from Wallog seawards
Pictures © Janet Baxter
Sarn-y-Bwlch is the smallest of the three Sarns extending some 6 kilometres offshore out from Pen Bwlch point at Tywyn in Gwynedd, and again with charted depths as shallow as 0.3 metres (Admiralty chart 1972).
While a more basic survey has being carried out on the largest and most northern reef ‘St Badrig’, very little detailed recording of sub-littoral species has taken place on Sarn-y-Bwlch at Tywyn, and Sarn cynfelin near to Aberystwyth.
FoCB is now engaged in this very exciting and pioneering work which started with the 2004 Sarns Pilot Survey's:
The primary purpose of the 2004 surveys were to establish whether there was any evidence that certain cetacea, particularly bottlenose dolphin (Tursiops truncatus) and harbour porpoise (Phocoena phocoena), were utilising these natural reefs as a resource for foraging and feeding. Ten days of survey were completed in 2004, mainly looking at Sarn Cynfelyn near Aberystwyth, but also Sarn-y-Bwlch at Tywyn. This work suggested that one particular location upon Sarn Cynfelyn was of interest to bottlenose dolphin, a possible hotspot for foraging activity and feeding (Hughes, 2004).
The FoCB aim of the Sarns Survey 2005 was to focus in a little more detail on Sarn Cynfelyn to further evaluate the area for cetacean activity. In addition it was hoped that a photographic log of feeding animals would be possible in order to identify prey species taken. All surface environmental data would be logged, along with tidal information. The previous year’s survey had indicated that sighting times for the bottlenose dolphin may be linked with times of high water when foraging was evident.
It was also the intention to investigate the benthos of Sarn Cynfelyn by means of diver survey, more specifically locations where sightings of these animals had been made whilst foraging or feeding. It may then be possible to correlate the associated foraging behaviour of these animals with the benthic information recorded and a photographic record. In this way it was hoped that a simple picture of preferred prey species for these animals could be built at given locations upon the Sarn.
The benthic information was gathered using accredited Seasearch methodologies and would also increase our very limited biological knowledge of this area. This was deemed important for the future management of the SAC and the variety of wildlife that frequent the area. Atlantic grey seal (Halichoerus grypus) sightings would also be recorded, along with any encounters of marine turtles.
A Lesser spotted Dogfish on the reef.
Pictures courtesy of Dr Jo Porter