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TERRESTRIAL AND

Spp.

Spp. New

FRESHWATER

Considered

to National

MOLLUSCS

Extinct

BAP List

No. of

No. of

Possible other

records in

1km

sources

database

squares

of data sets

Species

Present or absent in Norfolk

Little Whirlpool Ram’s-horn snail Anisus vorticulus

P

37

recorded since 1980

12

Swollen Spire Snail Mercuria similis (M. confusa)

P

?

?

County Recorder

Glutinous Snail Myxas glutinosa

A

3

-

57

Other survey work completed or in progress

Comments

Current UK Species Action Plan Occurs in unpolluted, calcareous waters in well-vegetated marsh drains. Internationally threatened - Over-frequent ditch clearance, nutrient enrichment due to fertiliser applications, and conversion of grazing levels to arable farming with associated water table lowering. Norfolk Action Plan published December 1998, revised January 2003. RDB Species Found at Wheatfen Broad, Rockland Broad and in the river Yare. It is also found in the Waveney where it has extended its range. Typically found on bare mud exposed at low tide beneath emergent vegetation such as Phragmites australis or Glyceria maxima. Declining – Salinity changes, flood defence works and climate change. New to national list of BAP priority species 2007 Last Norfolk record in 1968. Considered extinct in Norfolk. Endangered. Current Species Action Plan Occurs in clear, hard water which is free from fine sediment and nitrate/phosphate pollution. Marked decline in UK – Disturbance and pollution.

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