S4056 Anisus vorticulus - Ramshorn snail - JNCC - Defra

European Community Directive 

on the Conservation of Natural Habitats 

and of Wild Fauna and Flora 

(92/43/EEC) 

Second Report by the United Kingdom under 

Article 17 

on the implementation of the Directive 

from January 2001 to December 2006 

Conservation status assessment for : 

S4056: Anisus vorticulus - Little ramshorn whirlpool snail 

Please note that this is a section of the report. For the complete report visit http://www.jncc.gov.uk/article17 

Please cite as: Joint Nature Conservation Committee. 2007. Second Report by the UK under Article 17 on the implementation of the Habitats 

Directive from January 2001 to December 2006. Peterborough: JNCC. Available from: www.jncc.gov.uk/article17

Second Report by the United Kingdom under Article 17 on the implementation of the Directive from 

January 2001 to December 2006 

S4056 Anisus vorticulus Little ramshorn whirlpool 

snail 

Audit trail compiled and edited by JNCC and the Invertebrate Inter-Agency Working Group 

This document is an audit of the data and judgements on conservation status in the UK’s 

report on the implementation of the Habitats Directive (January 2001 to December 2006) for 

this species. Superscript numbers accompanying the headings below, cross-reference to 

headings in the corresponding Annex B reporting form. This supporting information should 

be read in conjunction with the UK approach for species (see ‘Assessing Conservation Status: 

UK Approach’). 

1. Range Information 2.3 

Anisus vorticulus is restricted to East Anglia and south east England. It is absent from 

Northern Ireland, Scotland and Wales. 

1.1 Surface area of range 2.3.1 

967 km 2 

The above estimate was calculated within Alpha Hull software, using extent of occurrence as 

a proxy measure for range (see Map 1.1), at a 10km resolution. The value of alpha was set at 

20km to reflect the dispersal capacity of this species 

Map 1.1 Current extent of occurrence 

and occupied 10 km-squares (1998-2006) 

Data sources provided in Section 6 

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S4056 Anisus vorticulus Little ramshorn whirlpool snail 1



1.2 Date of range determination 2.3.2 

1998 – 2005 

Records collected between 1998 and 2005 (the most recently available data) were used to 

calculate the current extent of occurrence. Records from this time period provide the best 

representation of current range as it is understood by experts. 

1.3 Quality of range data 2.3.3 

Moderate 

All known extant sites were surveyed as part of the Species Action Plan for A. vorticulus. 

Repeat visits between 1994-2007 have been made to the well-established sites i.e. Arun 

Valley, Pevensey Levels and Waveney Valley. Therefore, on the basis that this is not a 

complete inventory, data has been reported as moderate, rather than good. 

1.4 Range trend 2.3.4 and range trend magnitude 2.3.5 

Stable 

This species has always had a restricted distribution, but historically, its range did extend 

farther into Suffolk (see Map 1.2). Recent survey work has shown that the species is present 

at some sites in East Suffolk, but the work is not yet complete and has not been published (R. 

Baker pers comm.). At this scale the range of A. vorticulus has not changed since the 

Directive came into force in 1994. 

1.5 Range trend period 2.3.6 

1994 – 2005 

1.6 Reasons for reported trend in range 2.3.7 

Not applicable 

The species appears to be confined to ditches at mid to late stages of ditch succession, at least 

3 years after the ditch has been cleared/managed. It is thought that inappropriate 

management: over frequent cleaning and deep digging has contributed to population declines, 

and thus the gradual decline in range. Run-off from arable land may also be a contributory 

factor. 

1.7 Favourable reference range 2.7.1 

967 km 2 (Equal to current) 

The decision tree in Note 1 has been used as a guide in determining the favourable reference 

range estimate (see ‘Assessing Conservation Status: UK Approach’). 

A. vorticulus has always been a rare species, probably due to natural (geological, dispersal, 

chemistry etc) barriers that have contributed to a limited distribution of A. vorticulus in the 

UK. Although there has been a decline in range since the 1960s, it is difficult to conclude that 

the current range is insufficiently large to support extant populations for the foreseeable 

future. Therefore, although expert opinion is that management should target restoration 

towards this historic (1960’s) extent of occurrence, in line with guidance set by the EU 

Commission, the favourable reference range has been given as equal to current. 

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Map 1.2 Historic extent of occurrence 

and occupied 10 km-squares (1960-2006) 

Data sources provided in Section 6 

1.8 Range conclusion 2.8 

Favourable 

Current range is considered Favourable within the terms of the assessment. 

2. Population of the Species 2.4 

Historically, there appear to be records for 34 self-contained colonies/marshes (= 1kmsquare) 

in the south-east of England covering 18 10-km squares. Records since 1965 indicate 

only 13 10km squares have been occupied by A. vorticulus (24 colonies/marshes). The last 

round of monitoring in 1994-2000 indicated that the snail only existed in 5-7 of the 

previously recorded 10km squares (13 colonies/marshes). 

2.1 Population estimate 2.4.1 

7 10-km squares 

Map 2.1 shows that, between 1998 and 2006, A. vorticulus was recorded from 7 10kmsquares. 

2.2 Date of population estimate 2.4.2 

2002 – 2006 

The population was estimated at the end of the last UK biodiversity action reporting round. 

2.3 Method of population estimate 2.4.3 

3 = from comprehensive inventory 

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The current estimate was based on a complete inventory of all records of distinct marshes 

containing A vorticulus between 2002 and 2006. 

2.4 Quality of population data 2.4.4 

Good 

The estimate was based on a complete inventory. Therefore in accordance with the 

Commission’s guidance, data quality is good. 

2.5 Population trend 2.4.5 and population trend magnitude 2.4.6 

Decreasing 

Historically, data for this species is poor, because it has been based on historical references 

and papers, which rarely used grid references, and offer only vague references to marsh 

names. Historical data also includes fossil records from Kerney 1999, and therefore tends 

only to include presence/absence data. 

Historic records suggest that in 1965, the species was present in 24 colonies/marshes across 

13 10km-squares, with just 13 colonies/marshes in 5-7 squares by 2000 (A. Watson Pers 

comm.) 

In the 2005 biodiversity reporting round, A. vorticulus was reported as ‘declining’ 

(continuing/accelerating) (www.ukbap-reporting.org.uk). 

Data for the period 1998-2006 (see Map 1) indicate that A. vorticulus was recorded from 7 

10km squares, more recent survey work (collated in 2005) records a decline to 7 10km 

squares i.e. a decline of almost 25%. 

2.6 Population trend period 2.4.7 

2002 – 2005 

The trend reported is based on information collected for the 2002-2005 biodiversity reporting 

round. 

2.7 Reasons for reported trend in population 2.4.8 

3. Direct human influence (restoration, deterioration, destruction); 

5. Natural processes 

The species appears to be confined to the mid to late-successional stages of ditch succession, 

3 or more years after the ditch has been cleared/managed. Over-management of drainage 

ditches in many areas is thought to have cause population declines. 

2.8 Justification of % thresholds for trends 2.4.9 


2.9 Main pressures 2.4.10 

802 Management of aquatic and bank vegetation for drainage purposes: 

(a) more mechanical and effective machinery, (b) no rotational system in place so ditches are 

generally uniform and of similar character, (c) connectivity to suitable ditches is reduced, (d) 

the main drains usually IDB or EA ditches are being dredged more frequently, (e) the minor 

drains are generally being neglected. 

804 Flooding: 

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(a) Control of water has led to less frequent flooding and for shorter duration – this has led to 

reduced connectivity. 

910 Silting up: 

(a) due to larger farms and more emphasis on fencing, the more minor ditches are 

increasingly being neglected (b) this has led to less variety in the range of successional stages 

available required to support A. vorticulus. 

951 Drying out / accumulation of organic material: 

Refer to 910 above. 

2.10 Threats 2.4.11 

141 Abandonment of pastoral systems: 

(a) Due to larger farms and more emphasis on fencing, the more minor ditches are 

increasingly being neglected, (b) more mechanical and effective machinery leading to 

uniform ditches, (c) the switch to arable farming on some marshes has led to inappropriate 

ditch management and lack of poaching effect by cattle. 

800 Landfill, land reclamation and drying out, general: 

(a) The switch to arable farming on some marshes has led to inappropriate ditch management 

and lack of poaching effect by cattle. 

802 Management of aquatic and bank vegetation for drainage purposes: 

(a) More mechanical and effective machinery, (b) no rotational system in place so ditches are 

generally uniform and of similar character, (c) connectivity to suitable ditches is reduced, (d) 

the main drains usually IDB or EA ditches are being dredged more frequently, (e) the minor 

drains are generally being neglected. 

804 Flooding: 

(a) Control of water has led to less frequent flooding and for shorter duration – this has led to 

reduced connectivity. 

830 Canalisation: 

(a) The main drains usually IDB or EA ditches are being dredged more frequently leading to 

more sterile and uniform channels with no refuges or habitat niche for A. vorticulus. 

890 Other human induced changes in hydraulic conditions 

Saline intrusion threatens some sites. 

910 Silting up: 

(a) Due to larger farms and more emphasis on fencing, the more minor ditches are 

increasingly being neglected (b) this has led to less variety in the range of successional stages 

available required to support A. vorticulus. 

951 Drying out / accumulation of organic material: 

Refer to 910 above. 

2.11 Favourable reference population 2.7.2 

9 10-km squares (current is 25% below the favourable reference population) 

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The decision tree in Note 1 has been used as a guide in determining the favourable reference 

population estimate (see ‘Assessing Conservation Status: UK Approach’). 

Current trend is declining but, based on the information available, this trend is not likely to 

have exceeded 1% per annum since the Habitats Directive came into force. 

Based on recent survey work at Hooe Levels on the Pevensey Levels (Willing 2006 and pers 

comm.), the Hooe Levels represent one of the best locations for A. vorticulus, with 37% of 

ditches supporting this species. It may be appropriate, therefore, to set this as a minimum 

baseline target for other areas. Furthermore, it has been predicted that within a ‘good’ ditch 

for A. vorticulus, you should expect, at the appropriate time of year, to retrieve at least 200 

specimens from 5 sampling points (Watson & Ormerod 2004b). 

Thus, a ‘favourable’ population would ideally meet both of these criteria. Expert opinion, 

supported by evidence presented by Watson & Ormerod (2004a), suggests that most 

populations do not meet these criteria at present. Hence, based on this and Note 1, the 

favourable reference value has been given as 9 10 km squares i.e. 25% above current 

population levels. This is a conservative estimate. 

2.12 Population conclusion 2.8 

Unfavourable - Inadequate and deteriorating 

The favourable reference value is greater than the current estimate, but not by more than 

25%. The A. vorticulus population has therefore been assessed as Unfavourable – Inadequate 

and (to reflect trends) deteriorating. 

3. Habitat for the Species in the Biogeographic Region or Sea 2.5 

A.vorticulus has only been found in the UK within grazing marshes which are drained by 

ditches, rhymes, dykes etc. It occurs in the unpolluted, calcareous waters of well-vegetated 

marsh drains and is occasionally found with other uncommon or vulnerable molluscs such as 

Valvata macrostoma, Pisidium pseudosphaerium and Segmentina nitida and often found 

floating on the surface amongst duckweed (Lemna spp.). It also shows preference for ditches 

or channels of >3m in width and >1m in depth with a diverse flora but with a moderate 

emergent vegetative cover, and often occurs in ditches in wet fields that flood in winter, as 

this may be important in enabling young snails to colonise new ditches. 

3.1 Surface area of habitat 2.5.2 

Unknown 

Area of grazing marsh within occupied sites would provide a crude proxy measure for 

habitat. However at present, this is not known. 

3.2 Date of estimation 2.5.3 


3.3 Quality of data on habitat area 2.5.4 

Poor 

Distribution of grazing marshes is fairly well-known and recorded (Biodiversity Action Plan 

priority habitat, HMSO 1995). However, on the basis that an area estimate can not be 

provided at this time, quality of data is reported as poor. 

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3.4 Habitat trend 2.5.5 

Decreasing 

Losses of grazing marsh in the whole UK have been significant in the last 60 years, broadly 

resulting from ecologically insensitive flood defence works, agricultural intensification, 

declines in traditional management and eutrophication 

(www.ukbap.org.uk/UKPlans.aspx?ID=9). 

In recent years, agri-environment statistics suggest that coastal and floodplain grazing marsh 

is fluctuating, but probably still declining in the UK. In England, the national trend has been 

reported as increasing. However, in respect to A. vorticulus, outlier marshes (such as Lewes 

Brook) have been reported as deteriorating (Watson & Ormerod, 2004a), and expert opinion 

is that there is little scope for their return. Based on this, the overall trend is reported as 

declining. 

3.5 Habitat trend period 2.5.6 

2002 – 2005 

3.6 Reasons for reported trend in habitat 2.5.7 

3 = Direct human influence (restoration, deterioration, destruction) 

Declines in grazing marsh and associated ditch habitat across the UK are broadly attributed to 

ecologically insensitive flood defence works, agricultural intensification, declines in 

traditional management and eutrophication. 

3.7 Suitable habitat for the species (in km 2 ) 2.7.3 

Unknown 

It is known that there are approximately 300,000ha of grazing marsh in the UK. However, 

not all of this will be ‘suitable’ for the following reasons: 

1) Historically, this species has only been found in south-east England. Therefore extensive 

grazing marsh such as the Somerset Levels and Gwent Levels should be excluded from 

consideration; 

2) Only high quality grazing marsh supports this species; it is unlikely that the snail occurred 

on every grazing marsh in the south-east. They do not appear in (i) brackish marshes such as 

Stour Valley, Kent, and (ii) small marshes; 

3) This species is unlikely to occur on newly restored/created grazing marshes unless it was 

re-introduced; and 

4) Before the drainage of marshes and the creation of associated ditches, it was likely that this 

species would have occupied a different habitat i.e. large swamps/open water transition which 

probably still occur in parts of Europe. 

It could therefore be suggested that the area of suitable habitat will be less than 300,000ha. 

However, since the extent of this ‘less than’ has yet to be calculated, suitable habitat has been 

reported as unknown. 

3.8 Habitat conclusion 2.8 

Unfavourable-Inadequate and deteriorating 

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A. voriculus habitat is in decline, and it can not confidently be reported that “area of habitat is 

sufficiently large and habitat quality is suitable for the long term survival of the species” (as 

would be required for a judgment of Favourable under Annex C guidance), particularly since 

the biodiversity action plan for this habitat indicates only 3% of the existing grazing marsh 

habitat in UK is of good conservation quality (HMSO 1995). 

However, based on expert opinion, neither can it be reported as “clearly not sufficient for 

long term survival of the species” (as would be required for a judgement of Unfavourable – 

Bad). 

Therefore, since the broad habitat type for A. voriculus falls between these two categories, a 

judgement of Unfavourable – Inadequate and (to reflect recent trends) deteriorating has been 

made. 

4. Future Prospects 2.6 

Poor prospects 

“Species is likely to struggle unless conditions change.” 

This species has been the subject of a species action plan under the UK Biodiversity Action 

Plan, and is included on the revised UKBAP list. 

The significant decline of A.vorticulus from former strongholds such as Amberley 

Wildbrooks and Pulborough is of major concern. It may be that the snail is a boom and bust 

species. However, all evidence seems to indicate that it is an annual species that overwinters 

and breeds in the summer months. In a healthy system, numbers of A. vorticulus should 

therefore be consistent from year to year. 

It appears that poor connectivity within the individual marshes is preventing the dispersal of 

A. vorticulus to new ditches. As a ditch becomes silted and choked with vegetation the snail 

is unable to disperse into more recently cleared ditches. This is a result of 1) ditches being 

neglected and/or being cleared more frequently, 2) ditches being mechanically cleared, more 

effective, longer stretches leaving no refuge areas, 3) ditches being done collectively so no 

rotational system in place, 4) flooding is less frequent so not aiding dispersal across the 

marsh. 

Furthermore, although grazing marshes known to support A. vorticulus are generally either 

protected and/or under sympathetic management, sites such as Purborough Brook are still in 

decline (Willing 2004, 2005). Outlier marshes are deteriorating and there seems to be little 

scope for the return of A. vorticulus. 

Existing assessment of A. vorticulus is primarily focused on well-established sites, and yet 

even in these areas, there is no clear explanation as to why it is still in decline. The outlier 

sites have not been visited since 1994-2000 and no thoughts have been expressed as to 

whether A. vorticulus has a future at these sites. 

For these reasons, it can not confidently be reported that the species will “survive and 

prosper”. However, given the level of monitoring and management effort that this species 

received, the species is not predicted to go extinct. Hence, future prospects are reported as 

poor. 

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4.1 Future prospects conclusion 2.8 

Unfavourable – Inadequate 

Despite management, populations are continuing to decline. However, on the basis that long 

term viability is not considered to be at risk at present, in line with Annex C, the assessment 

is Unfavourable – Inadaqaute, rather than Unfavourable – Bad. 

5. Overall Conclusion 2.8 

Unfavourable – Inadequate and deteriorating 

Range has been assessed as Favourable; all other parameters have been assessed as 

Unfavourable – Inadequate. Population and habitat have also been identified as deteriorating. 

The Overall Conclusion is therefore also Unfavourable-Inadequate and deteriorating. 

The decline of A. vorticulus within traditional UK strongholds is a major concern as well as 

its apparent loss from outlier sites. It has always been a rare species in the UK confined to 

south east England, and any decline is likely to be significant within a European context. The 

UK population represents the most north-westerly distribution and most likely a distinct 

separate genetic pool. 

The dependency of the snail on a vulnerable habitat: grazing marshes of high conservation 

quality and their associated ditches. With a changing climate, it is likely that these wetlands 

will change and the apparent effect on the snail is still unclear. This in combination with the 

poor dispersal ability of the snail makes the overall assessment of this species very poor. 

Table 5.1 Summary of conclusions 

Parameter Judgement Grounds for Judgement (in 

accordance with Annex C) 

Range Favourable Range is stable and not smaller than the 

Population Unfavourable – Inadequate 

and deteriorating 

Habitat Unfavourable – Inadequate 

and deteriorating 

Future 

Prospects 

Unfavourable – Inadequate 

Overall Unfavourable – Inadequate 

Assessment and deteriorating 

*1=High, 2=Moderate, 3=Low 

favourable reference range 

Any other combination 

Population is below the favourable 

reference population, but not by more 

than 25% 

Any other combination 

Habitat is declining BUT, [in expert 

opinion] long term survival is not 

currently at risk due to current area and 

quality 

Despite management, populations are 

declining. No long term viability risks 

are foreseen at present. However, this 

may change if declines can not be 

stabilised. 

One or more Unfavourable - Inadequate 

but no Unfavourable - Bad 

Reliability* 

High – Expert opinion is that the concluding judgement accurately reflects the current situation based on a 

professional understanding of the species. For range, population, and habitat, quality of data used to establish 

the current estimate has been identified as “good”; data used to inform trends is comprehensive and up to date. 

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S4056 Anisus vorticulus Little ramshorn whirlpool snail 9 

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1 

3 

2 

2



Moderate – A greater understanding of the feature, or the factors affecting it, is required before a confident 

concluding judgement can be made by experts. For range, population, and habitat, the current estimate and/or 

trend are based on recent, but incomplete or limited survey data; or alternately, a comprehensive, but outdated 

(pre-1994) review. 

Low – Judgements, and comprising estimates, are based predominately on expert opinion. 

N/A – Assessment conclusion is “unknown”, on the basis of insufficient reliable information 

6. References 

ABRAHAM, F., ALLEN, S., HODGE, P. and WILLING, M.J. 1998. A survey of the flora 

and selected invertebrate groups of the ditches of the Lower Arun Valley. Arun Valley 

Countryside Project, Bognor Regis: Arun District Council, (unpublished report) 

CURSON, S., FREED, T., GREENAWAY T., HODGE, P., RYLAND, K. & WILLING, 

M.J. 2003 Baseline Biological Survey of the Lower Ouse Valley (Tarring Neville, Southease 

& Offham Marshes). Sussex Record Centre Survey Unit. Woods Mill. 

DOLPHIN ECOLOGICAL SURVEYS et al. 2002. Baseline Biological Survey of the Lower 

Ouse Valley. Report to English Nature, Lewes. 

HICKLIN, A.J. 1986. An evaluation of the nature conservation status of the Lewes Brooks 

drainage system, East Sussex. Wye Nature Conservancy Council. 

HINGLEY, M.R. 1979. The colonisation of newly dredged drainage channels on the 

Pevensey level (East Sussex) with special reference to gastropods. London: Journal of 

Conchology. 30: 105 - 22. 

HMSO, 1995a. Biodiversity: The UK Steering Group Report - Volume II: Action Plans. 

HMSO, London. 

KERNEY, M. 1999. Atlas of the land and freshwater molluscs of Britain and Ireland. Harley 

Books. 

KILLEEN, I.J. 2005. A Survey to determine the present status of Anisus vorticulus at sites in 

Suffolk and Norfolk. Report for Environment Agency. 

KILLEEN, I.J. & WILLING, M.J. 1997. Survey of Ditches in East Anglia and South East 

England for the Freshwater Snails Segmentina nitida and Anisus vorticulus English Nature 

Research Report 229. 

NIGGEBRUGGE, K., DURANCE, I., WATSON, A.M., LEUVEN, R.S.E.W. & 

ORMEROD, S.J. 2006. Dispersal and distribution in uncommon wetland gastropods: snailtrail 

or critical path? Unpublished. 

WATSON, A. 2002. The Ecology of Four Scarce Wetland Molluscs – University of Wales, 

Cardiff PhD study Environment Agency R&D Project W1-038PR. 

WATSON, A.M. & ORMEROD S.J. 2004a. The distribution of three uncommon freshwater 

gastropods in the drainage ditches of British grazing marshes. 

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WATSON, A.M. & ORMEROD S.J. 2004b. The microdistribution of three uncommon 

freshwater gastropods in the drainage ditches of British grazing marshes. 

WILLING, M.J. & KILLEEN, I.J. 1998. The freshwater snail Anisus vorticulus in ditches in 

Suffolk, Norfolk and West Sussex. English Nature Research Reports, No. 287. Peterborough: 

English Nature. 

WILLING, M.J. & KILLEEN, I.J. 1999. Anisus vorticulus – a rare & threatened water snail. 

British Wildlife, 10:6, pp 412-418. 

WILLING, M.J. 1999. Monitoring populations of Anisus vorticulus the little whirlpool 

ramshorn snail in West Sussex, May - November 1998. English Nature Research Reports 

310. Peterborough: English Nature. 

WILLING, M.J. 2000a. A baseline molluscan survey of the RSPB Pulborough Brooks 

Reserve. Unpublished report for the Environment Agency, Worthing. 

WILLING, M.J. 2000b. A molluscan survey of: 1. ditches adjacent to the middle River Arun 

& lower River Rother, West Sussex & 2. a monitoring ditch on Amberley Wildbrooks. 

Unpublished report for the Environment Agency, Worthing. 

WILLING, M.J. 2001. Molluscan monitoring of two ditches on Amberley Wildbrooks, 2000. 

Unpublished report for the Environment Agency, Worthing. 

WILLING, M.J. 2004. Monitoring populations of the little whirlpool ram’s-horn snail Anisus 

vorticulus (the little whirlpool ramshorn snail) at Pulborough Brooks and Amberley 

Wildbrooks June – September 2004. Unpublished report to the RSPB & Environment 

Agency (Worthing). 

WILLING, M.J. 2005. Monitoring populations of Anisus vorticulus (the little whirlpool 

ramshorn snail) at Pulborough Brooks & Amberley Wildbrooks June – September 2004. An 

unpublished report to the RSPB and Environment Agency (Worthing). 

WILLING, M.J. 2006. Monitoring, survey and translocation of populations of the little 

whirlpool ram’s-horn snail Anisus vorticulus at Pulborough Brooks, Amberley Wildbrooks 

and North Stoke June – November 2005. An unpublished report to the RSPB and 

Environment Agency (Worthing). 

WILLING, M.J. 2006. A survey for the Little Whirlepool Ram’s-horn snail Anisus vortiulus 

and other freshwater Mollusca at North Stoke: June 2006 Unpublished report to DEFRA 

Guildfords and North Stoke Farm. 

WILLING. M.J. 2007. The Survey & Monitoring of populations of the Little Whirlepool 

Ram’s-horn Snail on (a) the SWT Pevensey Levels Reserve and (b) Amberley Wildbrooks 

and Pulborough Brooks: May – June 2006. Sussex Biodiversity Records Centre Survey Unit. 

Woodsmill, Henfield. 

WILLING, M.J. 2007. Monitoring populations of the Little Whirlpool Ram’s-horn Snail on 

Pevensey Levels April 2006. Environment Agency, Worthing. 

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Map Data Sources 

Conchological Society - Mollusc (non-marine) data for Great Britain and Ireland; Natural 

England - Invertebrate Site Register (via the NBN Gateway). 

Data from KILLEEN, I.J. 2005. A survey to determine the present status of Anisus vorticulus 

(Gastropoda: Planorbiidae) at sites in Suffolk and Norfolk. Unpublished report for the 

Environment Agency. 

KILLEEN I.J. 1999. EN Species Recovery Programme: The freshwater snail Anisus 

vorticulus: 1998 monitoring survey of ditches in East Anglia. English Nature Research 

Reports No.311. Peterborough: English Nature. 

KILLEEN, I.J. & WILLING, M.J. 1997. Survey of Ditches in East Anglia and South East 

England for the Freshwater Snails Segmentina nitida and Anisus vorticulus English Nature 

Research Report 229. 

Natural England (A. Watson, pers. comm) compiled in 2000. 

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