Updates to Biodiversity Action Plan (BAP) designation

Records since 1970 would indicate that this species is nationally rare within the United Kingdom, particularly as it was once a highly �recordable' species due to its attraction to shell collectors. However, since the middle of the 19 th century when records were first systematically made there have been few occurrences in UK waters.

Over the last 20 years a decline in populations of Atrina fragilis have been recorded from the inshore waters of SW England, any abundances that have been recorded have come from deep water trawls (Hiscock & Jones, 2004). Before 1975 a population of Atrina fragilis was found within a scallop bed off Glengad Head. Dredging for Pecten maximus started in 1975 bringing up many live specimens and shells of Atrina fragilis in the dredges; it is thought that as a result of this dredging the population of Atrina fragilis has been destroyed (Anon, 1999). In the Isles of Scilly Atrina fragilis was recorded in Zostera sp. beds, however since the beds have been destroyed as a results of disease no specimens of Atrina fragilis have been recorded (Turk & Seaward, 1997).

Atrina fragilis is still at threat from decline due to its high vulnerability from scallop dredging and dermersal fishing. Environmental changes may also affect Atrina fragilis for example increases in pollutants, for example TBT, turbidity and sedimentation (Anon, 1999). This species is also likely to be affected by substratum loss and displacement due to its �high' sensitivity to many physical disturbance factors (Hiscock et al., 2005). The recruitment pattern of Atrina fragilis larvae may be affected by changes in seawater temperatures and current patterns (Anon, 1999).

Despite most Eunicella verrucosa populations being stable, populations at Lundy Island were affected in 2001 by a mysterious disease; as a result their densities are much lower. However, the loss and damaged that occurred at Lundy Island in 2001 is believed to be localised (Hiscock et al., 2005).

Although current decline in populations of Eunicella verrucosa has been localised this species still faces a number of threats. Disease like the one that occurred at Lundy indicates the potential effects that can occur, although the cause of the event is unknown and may be of natural origin (Hiscock et al., 2005). Eunicella verrucosa is vulnerable to physical disturbances including strikes by careless divers fins, fishing activities; nets and lines can cause damage to soft tissue, which can ultimately damage and kill colonies (Anon, 1999) and mobile fishing gear has also damaged populations in Lyme Bay (Hiscock et al., 2005). In March 2002 a number of broken Eunicella verrucosa were washed up on the beach at Lyme Bay entangled in monofilament nets indicating a potential threat to populations. Climate change posses a threat, firstly warmer sea temperatures can lead to possible nutrient enrichment which can encourage algal growth and may smother Eunicella verrucosa (Hiscock et al., 2005). Secondly, the warm-water barnacle Solidobalanus fallax is beginning to colonise Eunicella verrucosa in the south-west England and may spread to Pembrokeshire. Even though this species is unlikely to colonise healthy parts of a colony, bare skeleton may become vulnerable (Hiscock et al., 2005).

Limaria hians can be considered important on both a regional and global scale (J. Hall-Spencer, per. comm.). This species may occupy �nests' of byssus threads under stones and among rubble (Tyler-Walters, 2002), when this species is abundant the byssal threads form a �carpet' or reef over sand-shell (Muchin, 1995). Limaria hians provide biogenic reefs and support a wide range of epifauna and infauna (Hall-Spencer and Moore, 2000a).

Limaria hians are common in shallow water amongst oarweeds or horse mussel beds (Yonge & Thompson, 1976). However, numbers of these species have declined especially where the byssal threads have formed reefs and whole reefs have been destroyed. In the Clyde Sea area Limaria hians was once widespread and common on sublittoral gravel prior to the 1970s (Allen, 1962, Gilmour, 1967). However, recent studies have shown a decline Limaria hians in the Clyde Sea and the scallop dredging that has taken place over the past 30 years is likely to be the cause (Hall-Spencer & Moore, 2000a). A decline in Limaria hians was also noted within Mulroy Bay as a result of using TBT as an antifoulant on salmon cages between 1981-1985 (Minchin, 1995).

This species is at risk of further decline because it is highly sensitive to the effects of benthic fishing gear and the reefs that Limaria hians form can become ripped apart by towed fishing gear.

Victorella pavida is rare within the United Kingdom , known only to occur at one site, Swanpool, near Falmouth in Cornwall (Gainey, 1997).

This species was first discovered and described from two sites in London in 1870, Surrey Canal and Victoria Docks, however has now disappeared from both of these sites probably as a result of the reduction in water salinity which was caused through the docklands development (Gainey, 1997). It has since been rediscovered in the brackish water lagoon at Swanpool, but this remains the only site in the UK despite extensive surveys in the 1980s (Gainey, 1997).

As Victorella pavida is only found in one location, the threat of decline is high. Since 1945 the area of reedbed surrounding the lagoon has decreased dramatically due to succession to woodland (Gainey, 1997). Other factors that threaten Victorella pavida include silting, changes in salinity and effects from various pollutants, all of which can be caused by an increase in runoff as a result of development both industrial and residential (Gainey, 1997, Carter & Jackson, 2004).

Due to the fact this species is only found in one location in the UK it is very important to protect both the species and the habitat.

Within the United Kingdom Leptopsammia pruvoti is considered rare known only from a few sites including the Isles of Scilly, Lundy Island, Lyme Bay, Portland and off Plymouth Sound (Wood, 2005, Jackson, 2006).

A decline in populations of Leptopsammia pruvoti has been recorded over the past few years. Between 1993 and 1997 a 22% decline in population Leptopsammia pruvoti at Lundy Island had been recorded (Anon, 1999). This decline is still apparent as losses are exceeding new recruits (Wood, 2005). In 1969 populations of Leptopsammia pruvoti occurred near Ilfracombe in the North Devon, however are no longer believed to be present (Jackson, 2006). One reason behind declines in populations could be as a result of poor recruitment; larvae may be swept away by currents and become consumed by predators or settle on unsuitable habitats (Anon, 1999).

The threat of further decline is a problem as Leptopsammia pruvoti is a long-lived, vulnerable species that are slow to recover, particular as reproduction appears to be infrequent (Wood, 2005). There is evidence to suggest that recruitment may come from distant sources, including continental Europe . If this is the case then only when appropriate water bodies more towards south-west England will recruitment take place, this type of movement may take place every 25-30 years (Anon, 1999). Leptopsammia pruvoti lives permanently attached to the substrum, which would indicate that if the habitat is lost then so would this species. It is not just lose of substrum that threatens this species; two species of worms, a fan worm ( Potamilla reinformis ) and the horseshoe worm (Phoronis hippocrepia ) are known to bore into the base of the corallum (Wood, 2005). This can cause Leptopsammia pruvoti to become detached from the substrum and therefore lead to the death of the coral (Wood, 2005; Jackson 2006).

Maerl has a patchy distribution around the United Kingdom, there is however evidence to suggest a decline in this habitat has taken place and that the habitat is still at threat from further decline.

The threat of further decline of maerl beds can be considered high; these beds take time to establish and grow and are extremely long-lived, maerl can therefore be considered as a non-renewable resource (Hiscock et al., 2005). Maerl communities are vulnerable and easily damaged by dragged fishing gear, which reduces the long-term viability of the habitat (Hiscock et al., 2005). A study by Hall-Spencer & Moore (2000b) showed that scallop dredging caused a 70% reduction in maerl with no sign of recovery over the next four years. This indicates the threat to these habitats especially as scallop dredging is becoming more widespread.

Although the distribution of horse mussels ( Modiolus modiolus ) around the UK is quite wide, the distribution of Modiolus modiolus beds is restricted to northern waters (Hiscock et al., 2005). These beds are held together by byssal threads and can form complex reef structures supporting a great diversity of marine life, making them an important marine habitat.

A decline in Modiolus modiolus beds in the Irish Sea is believed to have occurred since records began in the 1950s due to the impact of mobile fishing gear (Veal et al., 2000). There has also been a decline in Modiolus modiolus in Strangford Lough. The Modiolus modiolus beds have been documented here since the middle of the 1800s and were considered extensive in the 1970s and 1980s (Roberts, 2003). However, the Modiolus modiolus beds now appear to be greatly reduced in extent (Roberts, 2003).

Modiolus modiolus beds have a poor recruitment rate and are therefore slow to recover from damage, it is also possible that these beds may not recover from severe damage like that caused by trawling (Hiscock et al., 2005). For this reason Modiolus modiolus beds are at risk from further decline in the future as a result of fishing in particular heavy trawl gear and coastal development, through changes in water flow and dredging through smothering as a result of dumping dredged sediment (Hiscock et al., 2005).

The Serpulid tube worm can be found attached to shells and stones in small numbers, however, these tubes can fuse together to form reefs (Minchin, 1987) known as Serpula vermicularis reefs. These reefs provide an important habitat for a diversity of marine life. Within the UK these reefs are rare, only known to occur in Loch Creran in Scotland and the Co Galway area in Ireland (Minchin, 1987; Moore et al., 1998).

In 1887 shallow reef beds of Serpula vermicularis were recorded in Loch Creran, however these beds are no longer present (Moore et al., 1998). A decline has also occurred along at stretch of coastline at the site of an alginate factory discharge in Loch Creran. Since the 1980s Serpula vermicularis beds in Loch Sween, the only other site in the UK, have also shown a decline (Hill, 2005).

Due to the fact that Serpula vermicularis are restricted to isolated locations there is a threat of further decline, particularly as a result of human activity. These threats include, scallop dredging, physical disturbance caused by mooring ground tackle and the discharging of organic factory effluent (Moore et al., 1998).