Hull Biodiversity Action Plan

Dun Sentinel (Assiminea grayana)

The Dun Sentinel is found in saltmarshes and estuaries at or just above the high-tide level, either in brackish pools or, more frequently, out of water, crawling on wet mud or sedges. It is more a terrestrial than an aquatic snail. It can often be found under stones or pieces of driftwood lying in marshy ground.

Mouse-eared Snail (Ovatella myosotis)

The Mouse-eared Snail is found in muddy, sheltered places at high-tide level in brackish estuaries and saltmarshes, often under driftwood and other flotsam. It lives mostly out of water and is more a terrestrial than an aquatic snail. Less often it inhabits shingle or the crevices of rocks in exposed situations. Bleached shells are sometimes common in tidal debris. It is probably a native species although in recent years there has been speculation about its status.

CURRENT STATUS

Dun Sentinel (Assiminea grayana)

This snail is found on the east coast of Britain. It is abundant where it occurs and gives no evidence of significant recent change. It was also recently discovered in the Shannon Estuary on the west coast of Ireland and may perhaps be a recent immigrant to that country. It is also found on West European coasts, mainly around the southern North Sea. The Humber Estuary represents its most northerly distribution in Britain. Within Yorkshire it is only known from two small areas of saltmarsh on the banks of the River Humber and it is considered vulnerable within the region.

Mouse-eared Snail (Ovatella myosotis)

This snail is found in scattered locations around the coast of Great Britain and Ireland. It is also found on the Mediterranean and West European coasts, north to the British Isles and Denmark. The Mouse-eared Snail remains common in suitable situations and gives no evidence of regional change. The fact that this species is usually abundant where it occurs tends to mean that it is not considered a species that requires conservation. However, in Yorkshire this is not the case. The habitat is very restricted and is easily destroyed.

The reedbeds bordering the River Humber at Hessle near the city boundary are now the main habitat for both of these species in Yorkshire.

CURRENT FACTORS AFFECTING THE HABITAT

Both snails are restricted to very specific saline habitats and loss of habitat due to sea level rise and development is affecting the species, for example, loss of habitat due to footpath creation and railway embankment work near Hessle.
Pollution may also affect these species.

CURRENT ACTION

Legal Status

Neither species have any international or national designations but they are listed as vulnerable in the Yorkshire Red Data Book for Land and Freshwater Molluscs.

Management, Research and Guidance

There is currently no information available on management for these species and no action for them in Hull.

ACTION PLAN AIMS

To continue monitoring the Dun Sentinel and Mouse-eared Snail.
To protect remaining area of saltmarsh.

WHAT WE ARE GOING TO DO

Action	Target	Partner	Aim
Policy and Legislation
No policy or legislation proposed.
Habitat Management and Protection
Protect remaining saltmarsh from development.	Ongoing: Do not allow any development or other activities that may negatively affect saltmarsh habitat.	KuHCC (Planning), EA	2
Advisory
No advisory actions proposed.
Future Research and Monitoring
Monitor populations of Dun Sentinel and Mouse-eared Snail.	Ongoing: Continued monitoring of distribution of Dun Sentinel and Mouse-eared Snail.		1
Communications and Publicity
No communication or publicity proposed.

WHAT WE CAN ALL DO

No communication or publicity proposed.

LINKS WITH OTHER ACTION PLANS

Protection of Estuarine Habitats is essential for the survival of the Dun Sentinel and Mouse-eared Snail.

REFERENCES

Kerney, M.P. (1999) Atlas of the Land and Fresh water Molluscs of Britain and Ireland. Harley Books.

Norris, A. (1998) Notes on Yorkshire Mollusca - Number 11: A Yorkshire Red Data Book for Land and Freshwater Mollusca. The Naturalist 123: 113-117.

Norris, A. (1999) List of mollusca recorded from the Country Park at Hessle, East Yorkshire.