South Wales Seasearch JM CW and Fan Shell survey 2003 Summary Report

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JM JM The Fan shell, Atrina fragilis The survey looked at sites in The primary purpose of these The Marine Conservation Society is Carmarthen Bay (last record 1899), surveys was to look for the Lead Partner for the Fan shell Milford Haven (last record 1960) populations of the rare Action Plan and organised and South Haven Skomer (diver Biodiversity Action Plan species this survey to look at the two sites of record from “about 20 years ago”). Atrina fragilis (the Fan shell). previous records in Wales and one We found a number of different where a scuba diver had reported sediment habitats which might This rare bivalve mollusc has seeing a fan shell. have contained fan shells, though only been reported from 2 the exact preference is not known. coastal sites in Welsh waters, None of the records were recent and At of one of the Carmarthen Bay and a further 30 coastal sites in nothing was known of the present sites there were many bivalves the UK and Eire. Offshore status of the populations in these present whist at the other sites populations numbers and three areas. numbers were smaller. population 'hotspots' are RH presently unknown, although The only clear evidence of the there are some historical records presence of fan shells comes from from scallop-trawl boat records of a single valve found amongst shell large populations off the west debris in Milford Haven (below). coast of Ireland and in the English This is a small shell, only 9cm long Channel. There are no currently and appears to be relatively recent. known 'hotposts' of populations CW of these and if they were located around the UK, they would immediately need The picture above is one of the very consideration for protected area few living fan shells currently known, status because of their rarity. having been brought up in a trawl and transplanted to a Scottish sea loch.

Carmarthen Bay The rocky areas at Woolhouse Rocks, The Yowan and Spaniel The survey looked at sites on the Shoal were low lying limestone reefs eastern side of Carmarthen Bay. covered in edible mussels (cover Because the main focus was on top left). The lowest rocks, where habitats where fan shells might Saundersfoot winter storms will scour them, had be found we looked at soft many long hydroids such as sediments both in open areas Sertularia argentea (back page). and around rocky outcrops, 5m Amongst the mussels were other where they might have survived hydroids, especially the sea beard trawling activities. Atrina record site Nemertesia (cover bottom left). Carmarthen The richest sediment site was in Bay the position given for the 1899 Tenby record of fan shells (Atrina 10m record site). Here we found fine Woolhouse The Yowan rippled sand with a variety of Rocks surface life such as whelks, brittle stars and other starfish including Astropecten irregularis Man of War below. Roads 20m Caldey Island CW There was a variety of mobile life living on the mussels. This included common octopus (above) There were also partly submerged and large numbers of common animals such as Sagartiogeton starfish and spider crabs (back anemones and sea potatos, and page). Edible crabs and lobster bivalve mollucs, especially razor were also present. Gullies at The shells, buried deep in the sandy Yowan had the best fish life sediment. The other sandy sites were JM including a conger eel, topknot and much poorer in animal life. a number of bib and poor cod. Milford Haven North of Stack Rock all the dives The location of the 1960 record of took place on flat sediment at a depth of 6-8m bcd. The Atrina fragilis from Milford Haven 5m Little Castle composition of the sediment was Stack Rock. This is towards Sandy Haven Bay Head varied but was patchy without any the western (entrance) end of the Location of South Hook haven on the northern side just Atrina shell Point clear zoning. Different habitats west of the last oil jetty. Our recorded were: 10m l surveys were concentrated Flat fine firm sand densely around Stack Rock for this reason. Stack Rock covered in Sand mason worms, l Waves of maerl debris with Esso Jetty There were algal dominated rocky Daisy and burrowing anemones, surfaces immediately around the Milford Haven tube worms and hermit crabs, rock itself but these rapidly gave 20m swimming crabs, prawns and way to soft sediments. Below gobies, l 5.5m bcd there were no boulders Thorn Point Mixed cobbles, shell debris, and the seabed consisted of a Chapel pebbles and mud, Bay l variety of sediments ranging from Mixed pebbles and fine sand mixed cobbles and gravel to with Sand mason worms and muddy fine sand. The softer The map shows the locations of bryozoans, l sediments had numerous burrows the dives carried out in Milford Small boulders on sand and and tubes, notably the sand Haven and the position of the one gravel. Horsehoe worms mason worm Lanice conchilega Atrina shell found. Phoronis hippocrepia (cover top right), sulphur sponge Suberites and the fan worms Branchiomma CW bombyx& Megalomma (right) . carnosus and bryozoans were all Also within the sediment were common. bivalves such asEnsis sp ., Arctica islandica,the king scallop Pecten Chapel Bay, on the south side of maximus and brittlestars the Haven, had a fine sand Amphiura sp. Burrows of the sediment with some shell and angular crab Goneplax occasional cobbles. The variety rhomboides were also commonly of animals was much less than seen (cover mid left). around Stack Rock.

Parsonquarry Bay Sheep Island and South South of Sheep Island Haven, Skomer The rocky walls of South Haven had a kelp forest to 5m depth and South Haven is a sheltered bay on This is a site on the south-west an animal turf on steep surfaces the south side of Skomer and in the facing coastline outside and just and algal turf on sloping surfaces Marine Nature Reserve. There was a south of Milford Haven. It is an below. Devonshire cup corals diver report of a fan shell here some area with few previous records. Caryophyllia smithii, and 20 years ago and the soft sediment in sponges were prominent in the the haven appeared to be a suitable The seabed consisted of high animal turf and edible sea urchins habitat for it. Two pairs of divers rocky ridges, running parallel with Echinus esculentus were swam across the shallower part of the the shoreline, and large boulders common. with patches of mud and silt pair and two other pairs explored opposite sides a little further out. between them. Shallower The soft sediments in the middle surfaces had kelp park and red of the bay ranged from sand to algal turfs, whilst deeper down the mud and contained few bivalves dominant cover was bryozoans and no fan shells. The soft mud with barnacles and cup corals. contained a number of interesting anemones, the daisy anemone There was a wide range of sponge Cereus (back page), burrowing fauna here, including the anemoneCerianthus lloydii and nationally scarce Thymosia dahlia anemone Urticina felina guernei. The yellow cluster are all fairly widespread but anemone Parazoanthus cylindrica and axinellae, another scarce species mitchellii are much was also present. 5 small less common - the latter crawfish,Palinurus elephas , were classified as nationally scarce also seen. (cover mid right).

Maps/chart reproduced/based on Admiralty chart 1482, 2878 & 3274 by permisson of the Controller of Her Majesty’s Stationery Office and the UK Hydrographic Office (www.ukho.gov.uk). Not to be used for navigation. The table to the right shows how many Phylum Common Name Number Common Species species were recorded in each group of Species and some of the most widely distributed species. Porifera Sponges 23 Boring sponge Cliona Sponges celata Anemones, corals, 29 hydroid Sertularia Relatively few sponges were recorded argentea and the majority were from the rocky hydroids, jellyfish Sea beard Nemertesia sites south of Sheep Island and at antennina South Haven. hydroid Obelia Two nationally scarce sponges were longissima Dead men’s fingers Alcyonium were found, the white Thymosia digitatum guernei (Sheep Island and South Daisy anemone Cereus Haven) and Axinella damicornis pedunculatus (South Haven). Both of these species Platyhelminthes Flatworms 1 Annelida Segmented worms 15 Sand mason worm Lanice Anemones, Corals, Hydroids & conchilega Crustacea Crabs, lobsters, barnacles 26 Barnacle Balanus Jellyfish crenatus Hydroids were very common (10 Hermit crab Pagurus species) especially at the low rocky bernhardus sites in Carmarthen Bay. Tall bushy Spiny spider crab Maja squinado hydroids commonly found here were Edible crab Cancer Sertularia argentea(below left) , Obelia pagurus longissima and the sea beard Velvet swimming crab Necora puber

Crabs and Lobsters Shells and Sea slugs Crabs and lobsters were common at This was the most diverse group with 40 different many of the sites. The rocky sites in species recorded. Mussels were abundant at the rocky sites in Carmarthen Bay (cover top left) JM CW Carmarthen Bay had large numbers of large spiny spider crabs Maja whereas scallops were more common in Milford Many of the anemones are typical squinado (below), as well as smaller Haven. There were a range of other bivalves sediment related species such as the hermit crabs,Pagurus spp. Edible within the soft sediments, especially in Daisy anemone Cereus pedunculatus crabs,Cancer pagurus , Lobster, Carmarthen Bay. There was a range of sea slugs (above right),Sagartia troglodytes and Homarus gammarus and Crawfish, present, many feeding on the hydroids (cover Sagartiogeton undatus. They include bottom left), including one nationally scarce two rarer species, Mesacmaea species, the attractiveThecacera pennigera . mitchelli(cover mid right), Peachia Octopus (inside) were seen at three sites. cylindrica (Skomer) and the burrowing anemoneCerianthus lloydii . Amongst Fishes rock dwelling anemones was the Fishes were relatively uncommon at most sites scarce Yellow cluster anemone, and no unusual species were seen. Sediment Parazoanthus anxinellae. dwelling species such a dragonets and sand gobies were common. Also present were Worms Female spider crab CW Thornback ray, Plaice, Flounder and Solenette. The most widely distributed worm was Starfish, Sea urchins the Sand mason worm, Lanice Nationally Rare and Scarce species conchilega which was especially and Sea cucumbers common at Stack Rock where, in one of The common starfish, Species Designation Where found the habitats, there was a densely Asterias rubens, was Sponge scarce South of Sheep Island abundant at the (frequent) packed ‘forest’ of these little worms Thymosia guernei South Haven (rare) Carmarthen Bay rocky Sponge scarce South Haven (occasional) Bryozoans sites where they were Axinella damicornis There were relatively few bryozoans feeding on mussels. Yellow cluster anemone scarce South of Sheep Is. Sediment areas had large (occasional) recorded during the survey. The most Parazoanthus axinellae common species was the soft finger numbers of brittle stars Anemone scarce South Haven (rare) bryozoanAlcyonium diaphanum , bothOphiura spp . on the Mesacmaea mitchelli which is typical of sediment and mixed surface andAmphiura with Crawfish BAP South of Sheep Is. their arms protruding from (occasional) ground sea beds. Two smaller Palinurus elephas bryozoansBugula plumosa and B. the sand. Sea potatos

This Seasearch survey was organised as a part of the Marine The survey was partly funded by the Countryside Council for Wales as a part of its Species Challenge Fund programme. Surveyors taking part were: Angela Read, Seasearch is a volunteer underwater survey project for Chris Pirie, Chris Wood, Christine Harling, recreational divers to contribute to the conservation of the Christine Webb, Dale Rostron, Darren Murray, marine environment. Financial support for the project during Dominic Smith, James Perrins, Jon Moore, Kirsten Ramsay, Lou Luddington, Rohan Holt, Sam Cook, Tim Theobalds and Vicki Bilings. Thanks to James Perrins for the use of his boat. This report has been prepared by Chris Wood.