AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 Published online 6 October 2004 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/aqc.630

The conservation of freshwater macroinvertebrate populations: a community-based classification scheme

RICHARD CHADD* and CHRIS EXTENCE The Environment Agency of England & Wales (Anglian Region, Northern Area), Waterside House, Waterside North, Lincoln, UK

ABSTRACT 1. A novel conservation indexing protocol is presented which aims to summarize aquatic macroinvertebrate data obtained from inland flowing- and still-water sites in Great Britain. Unlike other summary expressions of conservation value, the Community Conservation Index (CCI) accounts for community richness in the final analysis, as well as the relative rarity of species present. 2. Examples are provided to show how taxonomically rich ecosystems can obtain very high values of CCI that are broadly equivalent to CCI scores obtained from other sites supporting nationally rare species. In addition, the CCI is capable of local adjustment, to accommodate nationally common species occurring outside their normal range. 3. Examples show typical CCI outputs from a range of riverine and still-water habitats, and illustrate how this analysis can help in the day-to-day assessment and management of both lotic and lentic ecosystems. The index has already been used in legal submissions for public inquiries on Sites of Special Scientific Interest protected under British law and has contributed to the designation of such sites. It has also been used to inform management decisions on sites selected as candidate Special Areas of Conservation and as an operational tool using routinely obtained datasets. 4. The CCI provides an empirical basis for conservation initiatives, programmes and strategies, by producing a summary of aquatic invertebrate data over any appropriate scale of time and space. Furthermore, the final analysis need not be constrained by distribution of nationally rare species, but can indicate exceptionally rich or regionally unusual invertebrate populations. Copyright # 2004 John Wiley & Sons, Ltd.

KEY WORDS: Community Conservation Index; rare species; invertebrate conservation

INTRODUCTION

Consideration of aquatic macroinvertebrate communities is regarded as a useful tool for assessing the conservation status of inland wetland habitats, often for the purpose of influencing their ultimate fate. Such assessments may compare individual water bodies within a larger complex, to provide local management recommendations (Environment Agency, 1997; Painter, 1999), or to demonstrate a general conservation

*Correspondence to: Richard Chadd, Environment Agency, Stepping Stone Walk, Winfrey Avenue, Spalding, Lincolnshire PE11 1DA, UK.

Copyright # 2004 John Wiley & Sons, Ltd. Received 17 March 2003 Accepted 5 March 2004 598 R. CHADD AND C. EXTENCE principle (Collinson et al., 1995; Killeen, 1998; Standen, 1999). They may also be used to set the value of a particular site or habitat type, or a whole series of interrelated water bodies, in a national or international context (Environment Agency, 1993, 1997; Guest, 1997; Palmer, 1999; Harrison, 2000). Such information forms an integral part of the decision-making process for initiatives designed to protect and manage the aquatic environment, such as national abstraction licensing policies or asset management plans (Environment Agency, 2002). It also provides an essential contribution to national or international legislative requirements relating to biodiversity, such as the European Habitats Directive (EEC, 1992) and the resultant UK Conservation Regulations (HMSO, 1994). The usual approach when analysing available datasets is to discuss local, national or global value in subjective terms, such as the presence of one or more known rarities in the fauna. The judgement of rarity is set, in turn, by using published lists or reviews (e.g. Shirt, 1987; Bratton, 1991; Wallace, 1991) or atlases (e.g. Merritt et al., 1996; Kerney, 1999; Huxley, 2003). Alternatively, subjective judgements may use simple comparisons of species assemblages, so as to determine the degree of species richness associated with a site or region and/or their comparability with assemblages from similar waters elsewhere (Harrison, 2000). More objective approaches may involve the calculation of diversity parameters to derive a measure of species richness (Standen, 1999), or multivariate analysis to define community distinctiveness. This, in turn, may be augmented by a numerical index of species rarity (e.g. Collinson et al., 1995; Killeen, 1998; Pond Action, 1999). Community distinctiveness and species richness may also be used as a means of defining wetland typology and hydrology, so as to identify large-scale management options on specifically targeted areas. For example, studies of dry and intensively farmed ephemeral wetlands in the Prairie Pothole Region of North America (Euliss et al., 2001) allowed identification and evaluation of such habitats, even following draining or infilling, or when the wetlands were seasonally dry. The intention was for the technique to contribute subsequently to management strategies for the whole region’s wetland complex, focused on ‘value’ of particular sites as well as their hydrological state. In England and Wales, work on ponds and canals has led to the development of a ‘multimetric’ approach, known as the Predictive System for Multimetrics (PSYM). This uses a range of plant and invertebrate measures (‘metrics’) to define the general ecological condition of such wetlands (Environment Agency and Ponds Conservation Trust, 2002). Such metrics include, for example, the number of families of Coleoptera present. The assumption is that an ‘undegraded’ or ‘ideal’ ecology, determined for any pond or canal by reference to a national dataset obtained from still waters throughout England and Wales, can allow the determination of an overall quality state by comparing metrics obtained at a site with those predicted for it. This, in turn, may broadly equate to a measure of conservation status, although PSYM does not allow for invertebrate species rarity (one of the metrics used is an ‘uncommon species index’, but this is only applied to plants). Strictly speaking, PSYM is more suitable for assessing water quality rather than evaluating conservation status or potential. None of these approaches, however, combines a generalized measure of species rarity, as an index, with a numerical measure of taxon richness to derive an overall index of the conservation value of the whole community. Consequently, habitats supporting rare species cannot be compared directly with those colonized by invertebrate assemblages of unusually high richness, but lacking any particular rarities. It could, nevertheless, be argued that the latter are as distinct and worthy of protection as the former, and those habitats which combine both high taxon richness and high species rarity need particular acknowledgement. Furthermore, current indices, such as the Species Rarity Index (SRI) (Collinson et al., 1995; Pond Action, 1999), tend to rely entirely on species defined as nationally rare within published lists of status, such as the Red Data Books (RDBs; Shirt, 1987; Bratton, 1991). Species of limited distribution locally or nationally, but with no special status, do not contribute to the index score in this case. SRI is also limited by the fact that it cannot be applied to most riverine habitats, since it was specifically designed as a still-water assessment protocol.

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To some degree, many of the shortcomings in previous approaches to conservation assessment have been addressed by the development of the System for Evaluating Rivers for Conservation (SERCON; Boon et al., 1996, 1997). In this approach, rarity within invertebrate assemblages is allowed for by the use of status- weighted scores and species richness is derived from taxon counts. ‘Representativeness’ is incorporated by using predicted taxon lists and comparing these with the results obtained. The output is then adjusted by the presence of non-native species to characterize ‘naturalness’. Habitat availability is also assessed and weighted accordingly. The system also integrates macrophyte, fish and bird data in the overall assessment of a river site. SERCON is not, however, applicable to still waters and is not particularly simple to apply, as it requires access to predictive models and a large number of data sources. Therefore, the need exists for an index to address these various issues. Ideally, such an index should also allow for local flexibility, so as to emphasize communities that include nationally common species found outside their expected range. This principle has previously been used for expressing conservation status of ponds in East Yorkshire, UK, in terms of the resident hydrophytes (Linton and Goulder, 2000). Finally, the methodology should be robust enough to apply to all inland aquatic habitats: riverine or still water, permanent or temporary, freshwater or brackish. The technique described in this paper aims to summarize the conservation value of invertebrate communities in any inland aquatic habitat in Great Britain, in terms of a simple, adaptable and readily applied index (the Community Conservation Index (CCI)) which incorporates elements of both rarity and taxon richness.

METHODS

Species identified from a survey site or area are given a Conservation Score (CS), in accordance with the scheme outlined in Table 1. Joint Nature Conservation Committee (JNCC) designations of categories 10–5 are provided in Appendix 1. Appendix 2 lists the CSs assigned to those species of British macroinvertebrate which can be identified relatively easily, and for which adequate knowledge on conservation status is available. Scores have been assigned after reference to authoritative sources (Balfour-Browne, 1950, 1958; Hynes, 1977; Ellis, 1978; Elliott and Mann, 1979; Janus, 1982; Hammond, 1983; Shirt, 1987; Askew, 1988; Elliott et al., 1988; Friday, 1988; Savage, 1989; Bratton, 1990, 1991; Wallace, 1991; Falk, 1992; Foster and Eyre, 1992; Hyman, 1992, 1994; Kirby, 1992; Gledhill et al., 1993; Smaldon, 1993; Edington and Hildrew, 1995; Elliott, 1996; Merritt et al., 1996; Brooks, 1997; Bass, 1998; Disney, 1999; Kerney, 1999; Reynoldson and Young, 2000; Killeen et al., 2002; Huxley, 2003; Wallace et al., 2003).

Table 1. Conservation Scores (CSs) for freshwater invertebrate species in Great Britain CS Definition 10 RDB1 (Endangered) 9 RDB2 (Vulnerable) 8 RDB3 (Rare) 7 Notable (but not RDB status) 6 Regionally Notable 5 Local 4 Occasional (species not in categories 10–5, which occur in up to 10% of all samples from similar habitats) 3 Frequent (species not in categories 10–5, which occur in >10–25% of all samples from similar habitats) 2 Common (species not in categories 10–5, which occur in >25–50% of all samples from similar habitats) 1 Very Common (species not in categories 10–5, which occur in >50–100% of all samples from similar habitats)

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The upper range of scores is nationally agreed and, therefore, predefined, e.g. RDB1 species are automatically given the maximum score of 10. Lower scores for more common species have been assigned empirically, using the aforementioned reference texts, discussion with acknowledged experts, and drawing on personal experience, which included reference to relevant national datasets. These were drawn from the UK Environmental Change Network (ECN; Sykes et al., 1999), which amounted to over 1000 datasets, from 26 river sites and 16 still-water sites. The Environment Agency’s extensive routine monitoring programme was also used to assign CSs. This comprised 80 000 datasets, predominantly from river sites, but also including a large proportion of still-water sites. The still-water sites cover most of England and Wales and the river sites include 15 sites in Scotland. In addition to this, a number of ad hoc survey datasets (30) from various riverine sites in the Midlands, and in the south, south west, and south east of England were examined, as well as a 25 yr set of survey reports (approximately 1000 datasets, about 15% of which were from still waters) from the English counties of Lincolnshire, Cambridgeshire and Northamptonshire. For certain taxa it is recognized that characteristics for separating some species at certain life-stages are inadequately understood. This is true of many aquatic Diptera, for example (Martin Drake, pers. comm.), where it is not currently possible to separate certain species using larval or pupal material. Some of these species have, nevertheless, been included in Appendix 2, where information on distribution and concomitant classification is based on adult material. In this case, the only sensible option is to rear unidentifiable larvae or pupae obtained from aquatic habitats through to adult, so that identification becomes possible. Alternatively, survey work on aquatic habitats may need to be augmented by sampling of terrestrial zones, in order to obtain adult material of recognized water-dependent species. The absence of any rigorous definition of ‘aquatic species’ means that Appendix 2 is not comprehensive. It could be argued that virtually any invertebrate is, to some degree, ‘water dependent’. Some attempt has been made, however, to include species recognized as being specifically associated with water-dependent habitats, such as exposed riverine sediments (ERS; Eyre and Lott, 1997; Sadler and Petts, 2000). Although the species themselves are not truly aquatic (certain carabid and staphylinid Coleoptera are included, for example), the strict dependence of their habitat on the nearby river and the national importance of such communities makes their inclusion essential. Species only tenuously linked to aquatic habitats, such as Coleoptera found in damp leaf litter in woodland, have not, however, been included. In addition, not all of the fully aquatic species in Britain have been classified. In many cases, this is because of insufficient current information on status and/or habitat, so that it is not possible to assign meaningful CSs. Inclusion of relatively common species from certain groups is also precluded, because practicality or difficulty in identification means that these are infrequently identified in samples from aquatic habitats. Therefore, for certain groups it was decided to restrict the list of taxa assigned CSs in Appendix 2 to species in the upper four categories (scoring 7 to 10). For example, most of the Diptera (with the exception of Dixidae and Simuliidae, for which simple keys and adequate information on status exist) only have scores assigned for rare species. This is also the case for species in water-dependent but not strictly aquatic habitats, such as ERS. Such an approach avoids excessive expansion of the list of species assigned CSs, so that the document and methodology remain easy to use. This does not, of course, preclude adjustment of the usable list by individual practitioners. It is perfectly possible to expand the list to include further members of specialist invertebrate groups, using new publications or specialist knowledge, as long as the rules for assigning CSs are followed rigorously. Likewise, changes in threat categories and national status of individual species will result in subsequent adjustments in CSs following the same rules. Likely future changes in the UK Red Lists following the example used for plants (Palmer et al., 1997; IUCN Species Survival Commission, 1999, 2001) will make such revision essential. The CSs given in Appendix B can also be adjusted to provide a regional perspective, in that allowance can be made for locally rare but nationally common species and vice versa. Stenothermic flatworms, for example, are rare in lowland areas of Britain, although abundant and commonly encountered elsewhere. A specific example is Phagocata vitta, which may be assigned a CS of 6 in lowland regions, where it is

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) CONSERVATION OF FRESHWATER MACROINVERTEBRATE POPULATIONS 601 considered a rarity in surface waters (Reynoldson and Young, 2000). In a national context, it is relatively common and widespread, reflected in a CS of 3. Conversely, other species, such as the water beetle Hygrotus versicolor, might have their scores locally reduced, on the basis that they are commonly encountered in some parts of the country but are much less likely to be found in a sample taken elsewhere (Friday, 1988). Care should be exercised in the case of the latter, however, as certain regions in Britain might be the national ‘stronghold’ for a particular species, so that their contribution to an overall index score is of national importance. This procedure is particularly applicable to those species that have been assigned a CS of 6 (Regionally Notable), such as the lepidostomatid caddis Lasiocephala basalis. This species is not especially uncommon in Yorkshire and Dorset, where it should be regarded only as Local (Wallace, 1991) and reassigned a CS of 5 in any calculation of CCI. There are very few records for the species from other parts of Britain, however, and it is regarded as Notable in Scotland (Wallace, 1991). Use of the species in CCI calculations from regions other than Yorkshire and Dorset should, therefore, retain the CS of 6. Although adjusted scores are for local application only, the final index score thus generated might be of national significance in highlighting important ‘outliers’ from the usual species distributions, as well as making the index more locally relevant. It is considered essential, therefore, that ecologists using this method are able to redesignate appropriate species with any CS between 1 and 6. This must, however, be undertaken with strict reference to current peer-reviewed and published knowledge, not simply using local perspectives, so as to avoid conflicts of opinion. In changing the CS for species of Trichoptera, for example, a practitioner may refer to the JNCC review of the family (Wallace, 1991). For Coleoptera, regional adjustments, at least for Wales, the Midlands, Lincolnshire and northern East Anglia, might use ‘species quality scores’, a ranking of relative species status across these regions (Foster and Eyre, 1992). Any reported output including such redesignation of CSs should refer to the appropriate publication, so that there is complete clarity in the process. Clearly, greater credence can be placed on redesignation of scores where the appropriate reference text for any given species is the most up-to-date publication available. It is important to note that CCI calculation does not require the mandatory identification of all taxa obtained from a sample. Index scores will still be of value, provided species-level identification of a reasonable range of taxa has occurred. Clearly, the greater the size of the species dataset obtained, the better the resolution of the final index score. After the identification process is complete and individual CSs have been assigned to all appropriate species, the sum of the CSs is then calculated and divided by the number of contributing species to give a mean measure of conservation value. This is then multiplied by a Community Score (CoS; see Table 2), so that P CS CCI ¼ CoS ð1Þ n

The CoS may be derived from the rarest taxon present in the community (CSmax). For example, a dataset including an RDB3 species (CS=8), will have a CoS of 10. Alternatively, the Biological Monitoring Working Party (BMWP) score (Chesters, 1980) is used, following the ranges outlined in Table 2, to obtain the appropriate CoS. A sample achieving a BMWP score of 175, for example, would be assigned a CoS of 7. When this process produces different CoSs for a given sample, then the highest of the two alternative CoSs is used to calculate the CCI (in this example, a CoS of 10 would be used). The BMWP score has been used in this method as a convenient measure of species richness, as its positive relationship with habitat is accepted and well understood (Armitage et al., 1983). This relationship was tested in the development of a habitat-sensitive water quality index summarizing the elements of the BMWP system. The Lincoln Quality Index (LQI; Extence et al., 1987; Extence and Ferguson, 1989) used analysis of long-term invertebrate datasets obtained from approximately 400 sites in the English Midlands. This encompassed a range of habitats, such as fen drains, baseflow-driven rivers and rivers on impermeable catchments, and included water bodies of widely varying size.

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) 602 R. CHADD AND C. EXTENCE

Table 2. Community Score (CoS) categories

CoS BMWP Highest CS (CSmax) 15 >301 10 12 251–300 9 10 201–250 8 7 151–200 7 5 101–150 5 or 6 3 51–100 3 or 4 1 1–50 1 or 2 0 0 Scoring taxa absent

The BMWP ranges that define CoSs (BMWP) were derived with reference to the Environment Agency’s national dataset, comprising approximately 280 000 separate taxon lists and associated BMWP scores (in addition to national datasets obtained from the UK ECN and ad hoc survey data mentioned previously). Taxa identified to generic or family level are not assigned a CS. These taxa may, however, increase taxon richness, as reflected in the BMWP score, and thus influence the final calculated CCI. CCIs can range from 0 to >40, but a general guide to interpretation of scores is as follows: 0.0 to 5.0 } sites supporting only common species and/or a community of low taxon richness. Low conservation value. >5.0 to 10.0 } sites supporting at least one species of restricted distribution and/or a community of moderate taxon richness. Moderate conservation value. >10.0 to 15.0 } sites supporting at least one uncommon species, or several species of restricted distribution and/or a community of high taxon richness. Fairly high conservation value. >15.0 to 20.0 } sites supporting several uncommon species, at least one of which may be nationally rare and/or a community of high taxon richness. High conservation value. >20.0 } sites supporting several rarities, including species of national importance, or at least one extreme rarity (e.g. taxa included in the British RDBs) and/or a community of very high taxon richness. Very high conservation value (potentially of national significance and may merit statutory protection). These classifications of CCI were derived by testing the index over a 10 yr period. As with any set of generalized rules, there will inevitably be some drift at the boundaries of these ranges. For example, a dataset of low taxon richness, including very common species and a single national rarity, might drop into a relatively lower category of overall conservation value. The CoS concomitant with the presence of a national rarity should allow for this, however, and ensure that the overall index score still falls within one of the higher bands, if not the highest. Clearly, it would be unwise to preclude expert opinion when determining the overall conservation value of a site. The CCI is simply a tool to facilitate this process.

RESULTS

Large, lowland river reach of moderate taxon richness, supporting rare species Whitchurch Weir (SU633768) is situated in the middle reaches of the River Thames, upstream of the town of Reading in Berkshire, in south east England. In this reach, just downstream of its confluence with the River Pang, the Thames is ca 50 m wide and 2.5 m deep, with a level, firm gravel/sand substratum and regular, non-turbulent flow. In addition to the presence of a gravel matrix of unusual structure, stands of mature marginal willow trees (Salix spp.) have formed extensive root complexes, resulting in colonization of the reach by a unique invertebrate fauna.

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In the autumn of 2000, the site supported two RDB species and one nationally notable species, as well as other species of restricted distribution. A number of common species were also present, constituting an overall fauna of moderate to high richness, indicating water of generally good quality. Analysis of the overall conservation ‘value’ using CCI thus resulted in a fairly high average CS, coupled with a CoS multiplier (CSmax) that took into account the presence of rare species rather than overall taxonomic richness (Table 3). The final CCI score, in excess of 30, indicates a river reach of national significance, worthy of the highest possible legislative protection.

Lowland river reach draining semi-upland catchment, of very high taxon richness, but supporting generally common species The River Axe rises in the rural hill country of western Dorset in south west England, and drains south and west into eastern Devon, through Axminster, to Lyme Bay. It is a fairly small river, 40–50 km in length and, in its middle reaches at Weycroft (ST308000), is ca 7–8 m wide and 30–40 cm deep, flowing as a riffle/glide habitat over a predominantly cobble/pebble substratum. The fertile, calcareous chemistry and absence of any significant environmental stress means that the river supports a rich growth of macrophytes, with a resultant invertebrate fauna of high species richness. A total of 58 identifiable species from 36 families were present in 1994, with a further seven families and two groups that were not identified to species level. All of the species were generally common, however, with the rarest being classed as Regionally Notable (there were no nationally rare species), so CCI analysis resulted in a somewhat lower average CS than was achieved from the Thames at Whitchurch Weir (Table 4). The very high BMWP score, however, means that the CSmax was defined by overall taxon richness, CoS (BMWP), rather than the rarest species present, and was therefore fairly high. The resultant CCI of 23.8 thus indicates a river reach of broadly equivalent national significance to that in the Thames at Whitchurch Weir, despite the absence of genuinely rare species. This concurs with the riverine Site of Special Scientific Interest (SSSI) designation under UK conservation law (HMSO, 1981) afforded to the River Axe.

Upper reach of spring-fed calcareous stream in the English Midlands, of fairly low taxon richness, supporting species outside their normal range of distribution Wyville Brook is a calcareous spring-fed tributary of Cringle Brook, a major tributary of the Upper River Witham, near Grantham in western Lincolnshire, England. It rises in low limestone hills straddling the Lincolnshire–Nottinghamshire border, flows eastwards for 4–5 km, joining Cringle Brook at Stoke Rochford. The middle reaches of Wyville Brook, the lower Cringle Brook and the Upper Witham all support a thriving population of Atlantic stream crayfish (Austropotamobius pallipes), a protected species. The data presented in Table 5 were obtained from the primary spring source of Wyville Brook at SK882296. Spring flows at this site were emerging from below a low limestone shelf, situated in a plantation of larch (Larix decidua), before descending over a series of tiny cascades formed by limestone slabs. Apart from the predominant stable substratum, there was a fair amount of loose limestone gravel and twiggy debris on the bed of the stream. The channel was no more than 2 m wide and 2–5 cm deep. In the absence of any human impact (the spring was apparently permanent and probably unpolluted, judging by the sensitivity of the resident invertebrates), the only restriction on the fauna was imposed by the habitat. Taxon richness was consequently comparatively low. In addition, the site did not support any species of national rarity (there was a single species of stonefly, and a blackfly associated with spring heads, both of which have been rated as ‘local’, but all other species were generally common). However, several of the species occurred outside their usual range of distribution. The flatworm Crenobia alpina is a stenothermic species, found commonly in upland waters, but only appears in lowland Britain in streams maintaining year-round temperatures lower than 158C (Pateee,! 1966, cited in Reynoldson and Young (2000)). Likewise, the caseless caddisflies Wormaldia occipitalis and Plectrocnemia geniculata are

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Table 3. Aquatic invertebrate sample data (River Thames, Whitchurch Weir, Berkshire, 25/10/00) Taxon present CS Viviparus viviparus 3 Potamopyrgus antipodarum 1 Bithynia tentaculata 1 Lymnaea peregra 1 Lymnaea stagnalis 1 Physa fontinalis 1 Gyraulus albus 1 Armiger crista 2 Ancylus fluviatilis 1 Unio pictorum 3 Anodonta sp. – Sphaerium sp. – Oligochaeta (indet.) – Piscicola geometra 2 Hydracarina (indet.) – Asellus aquaticus 1 Corophium curvispinum 3 Crangonyx pseudogracilis 1 Ephemera lineata 9 Ephemera vulgata 4 Caenis luctuosa 1 Calopteryx splendens 2 Gomphus vulgatissimus 7 Polycentropus flavomaculatus 2 Lype reducta 3 Hydropsyche contubernalis 4 Hydroptila sp. – Molanna angustata 2 Mystacides longicornis 1 Leptocerus lusitanicus 9 Ceratopogonidae (indet.) – Chironomidae (indet.) – P CS=n 65/24=2.71 BMWP 134 CoS (BMWP) 5 a a CoS (CSmax) 12 CCI 2.71 12=32.5 (very high value) a Choice of CoS. much more common and widespread in the upland north and west of Britain and, like Crenobia, are considered Regionally Notable in south east England and East Anglia (Wallace, 1991). The conservation ‘value’ of the site can be analysed at two levels: first, applying national CSs (as presented in Appendix 2), results in a CCI indicating ‘fairly high’ value. The average CS is substantially raised by using enhanced CSs (shown in parentheses in Table 5), which allow for Regionally Notable species. Therefore, although the CoS multiplier is the same for both (BMWP is, of course, identical, and accounting for the rarest species still uses the same level of multiplication), the final CCI indicates ‘high’ conservation value, one level up from the analysis using national scores alone. Redesignation of scores for the three species was made, in this case, with reference to the Freshwater Biological Association guide to flatworms (Reynoldson and Young, 2000) and the JNCC review of Trichoptera (Wallace, 1991). The site,

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Table 4. Aquatic invertebrate sample data (River Axe, Weycroft, Devon, 04/05/94) Taxon present CS Polycelis sp. – Theodoxus fluviatilis 3 Potamopyrgus antipodarum 1 Bithynia tentaculata 1 Lymnaea peregra 1 Ancylus fluviatilis 1 Pisidium sp. – Oligochaeta (indet.) – Glossiphonia complanata 1 Helobdella stagnalis 1 Theromyzon tessulatum 2 Erpobdella octoculata 1 Piscicola geometra 2 Hydracarina (indet.) – Asellus aquaticus 1 Gammarus pulex 1 Baetis fuscatus 4 Baetis scambus 4 Baetis buceratus 6 Baetis rhodani 1 Baetis muticus 2 Rhithrogena semicolorata 2 Heptagenia sulphurea 4 Heptagenia sp. – Ecdyonurus torrentis 2 Ecdyonurus sp. – Ephemerella ignita 1 Ephemera danica 1 Caenis luctuosa/macrura – Caenis rivulorum 5 Amphinemura sulcicollis 2 Leuctra geniculata 4 Leuctra hippopus 3 Isoperla grammatica 2 Chloroperla torrentium 1 Calopteryx virgo 5 Aphelocheirus aestivalis 5 Brychius elevatus 3 Dytiscidae (indet.) – Orectochilus villosus 3 Anacaena limbata 1 Elmis aenea 1 Limnius volckmari 2 Oulimnius tuberculatus 2 Sialis lutaria 1 Rhyacophila dorsalis 1 Polycentropus kingi 5 Psychomyia pusilla 4 Hydropsyche pellucidula 2 Hydropsyche siltalai 1 Cheumatopsyche lepida 4 Hydroptila sp. – Anabolia nervosa 2 Mystacides longicornis 1

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Table 4. Continued Taxon present CS Athripsodes cinereus 1 Lepidostoma hirtum 2 Lasiocephala basalis 6 Brachycentrus subnubilus 6 Sericostoma personatum 1 Ceratopogonidae (indet.) – Chironomidae (indet.) – Atherix marginata – Chelifera sp. – Clinocera sp. – Hemerodromia unilineata – P CS=n 119/50=2.38 BMWP 238 CoS (BMWP)a 10a CoS (CSmax)5 CCI 2.38 10=23.8 (very high value) a Choice of CoS. therefore, becomes more important nationally because of its location, as an important outlier for certain species, rather than because of a resident population of ‘genuine’ rarities.

CCI calculations from a range of sites in Great Britain These examples (Table 6) show a series of index scores from habitats throughout Britain, including still waters and rivers from a variety of topographies and geological types. Sites range from very high value to low value, concomitant with statutory designation in the upper range of scores, and habitat degradation, caused by pollution, physical modification, navigation activity and other stresses, in the lower range. Mid- range scores were associated with high quality, broadly ‘pristine’, but currently undesignated sites. The choice of CoS (BMWP or CSmax) used in calculation varied substantially across the series of datasets. The example from Orton Brickpits shows a range of scores, indicating very high to fairly high value, obtained from a series of still waters at a single, well-defined habitat. The scores concur closely with known physical condition and water quality in the ponds, in that those which scored in the lower range, though still relatively important in a national sense, were either of a more uniform or less unusual habitat structure, or they exhibited signs of being excessively enriched. One of the ‘less valuable’ ponds supported a stock of introduced coarse fish. The ponds at Orton associated with higher CCI scores were the more unusual habitats, being highly variable in structure and consequently richer (some ephemeral and some permanent). All of these supported nationally rare species of plants, such as Chara canescens (RDB1), and rare invertebrates.

DISCUSSION

The examples presented here show a clear trend of usable summary data that allow practical input to conservation issues involving inland waters in Great Britain. The method has already been used successfully in a number of cases. In Peterborough (Cambridgeshire, England), it contributed to the designation of the Star Pit SSSI and it has also helped to inform management activities at Orton Brickpits

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Table 5. Aquatic macroinvertebrate sample data (Wyville Brook, Lincolnshire, 22/02/02) Taxon present CSa Polycelis felina 3 Crenobia alpina 2 (6) Eiseniella tetraedra – Gammarus pulex 1 Baetis rhodani 1 Nemoura erratica 5 Elodes sp. – Elmis aenea 1 Agapetus fuscipes 1 Wormaldia occipitalis 2 (6) Lype reducta 3 Plectrocnemia conspersa 2 Plectrocnemia geniculata 3 (6) Micropterna sequax 1 Tipula sp. – Hexatoma sp. – Dixa submaculata 4 Simulium costatum 5

PNationally applicable analysis CS=n 34/14=2.43 BMWP 80 CoS (BMWP) 3 b b CoS (CSmax) 5

CCI 2.43 5=12.2 (fairly high value)

PLocally applicable analysis CS=n 52/14=3.71 BMWP 80 CoS (BMWP) 3 b b CoS (CSmax) 5 CCI 3.71 5=18.6 (high value) a Locally adjusted scores in parentheses where applicable. b Choice of CoS.

candidate Special Area of Conservation (cSAC). The method has also been applied to the assessment of potential riverine SSSIs in the English Midlands and to appraise Lincolnshire chalk streams, to fulfil obligations set out in the UK Biodiversity Action Plan (BAP; The UK Biodiversity Steering Group, 1995). CCI was a primary component of the conservation submission for the Dibden Bay Public Inquiry (Tim Holzer, pers. comm.). In this case, an assessment was made of the value of aquatic macroinvertebrate communities colonizing a coastal watercourse, rising in the New Forest in Hampshire (southern England), that was threatened by marine development plans. In this case, re-evaluated SRI scores (Pond Action, 1999), used by contractors working on behalf of the developer, were compared with CCI analysis of the data in order to validate the SRI outputs. The use of an index of water quality, in this case the BMWP score, as a means of allowing for taxon richness is defensible. Primarily, this is because the positive association of the BMWP score with habitat richness is well known (Armitage et al., 1983; Extence et al., 1987; Extence and Ferguson, 1989), but also

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Table 6. CCI calculations from a range of flowing and still-water sites in Great Britain P Site and survey date Notes CS=n BMWP CSmax CoS (BMWP)/ CCI a CoS (CSmax) River Wye, Monmouthshire, Lower reach of very large, high- 3.15 227 9 10/12 37.8 Wales (SO536098), 2002 quality river catchment. Designated cSAC and SSSI. UK ECN site River Frome, Dorset, High-quality southern English chalk 2.64 269 6 12/5 31.7 England (SY890867), 2002 stream, with substantial baseflow. BAP habitat. UK ECN site Orton Brickpits, Peterborough, Extensive, mildly saline lowland 3.16 102 8 5/10 31.6 Cambridgeshire, England pond complex, derived from brick (TL165945), 04/96 workings, with a range of pond 3.32 67 7 3/7 23.2 age (2 to ca.100 yr) and variable 2.36 119 6 5/5 11.8 structure. Designated SSSI and 3.16 103 8 5/10 31.6 cSAC 2.92 71 8 3/10 29.2 3.54 96 8 3/10 35.4 2.42 66 7 3/7 16.9 2.68 118 7 5/7 18.7 River Eden, Cumbria, Middle reach of fairly large 2.41 255 7 12/7 28.9 England (NY604282), 2002 upland river catchment. Designated SSSI and cSAC. UK ECN site River Coquet, Warkworth, Lower reach of moderately large, 2.52 222 7 10/7 25.2 Northumberland, England high-quality, semi-upland river. (NU234061), 2002 Designated SSSI and cSAC. UK ECN site River Cree, Newton Stewart, Lower reach of large upland, 2.51 243 7 10/7 25.1 Dumfries and Galloway, afforested river catchment, on Scotland (NX412653), 2002 granite-dominated geology. UK ECN site River Tees, upstream of Cow High-quality upland headwater 2.44 160 6 7/5 17.1 Green Reservoir, County (530 m AOD) of major river Durham, England (NY761339), catchment. Underlying geology of 22/10/97 impermeable igneous type Loch Katrine, Perthshire, Deep oligotrophic lake in south 2.38 126 7 5/7 16.7 Scotland (NN486082), 2001 west highlands of Scotland. UK ECN site Loch Leven, Fife, Scotland Eutrophic, shallow glacial lake, 1.54 139 4 5/3 7.7 (NO135011), 2001 with fairly large, mixed-use catchment. UK ECN site Dallington Lake, Northampton, Highly artificial, mildly polluted 1.67 75 4 3/3 5.0 England (SP733620), 18/04/90 urban fishing lake, supporting alien crayfish River Ancholme, Cadney, North Middle reach of fairly large, 1.35 95 4 3/3 4.1 Lincolnshire, England extensively channelized lowland river (TA001029), 23/05/96 navigation. High water quality

River Holme, Honley, West Small, semi-upland urban river, 1.14 36 2 1/1 1.1 Yorkshire, England (SE142119), polluted with industrial and urban 11/11/97 effluents a CoS used in calculation is in bold typeface.

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) CONSERVATION OF FRESHWATER MACROINVERTEBRATE POPULATIONS 609 because an aquatic habitat achieving a very high BMWP score as a result of high water quality is intrinsically worthy of protection. A further measure of the ‘value’ of an invertebrate assemblage may be derived from its ‘representativeness’, i.e. the degree by which it represents a specific community type as a part of the national or international ‘pool’ of organisms. Such community types may be impoverished not because of human influence, but because this reflects their natural state (oligotrophic streams in the Scottish Highlands, for example). SERCON (Boon et al., 1996, 1997, 2002) allows for this, by statistically comparing observed taxa against those predicted and modifying outputs if alien species are present. This is an approach which is beyond the scope of the more simple methodology described here, although in many low-energy systems the measures of water quality tend to be high. Using the BMWP score as the multiplier for taxon richness may, therefore, address this apparent shortcoming, at least in some instances. As mentioned previously, CCI is only a tool to assist in value judgement. Its use must never be allowed to preclude expert opinion. All of the examples presented thus far have used CCI for spatial assessment of variation in conservation, either by comparing sites within a local area or by setting sites in a national context. It is also possible to use the methodology to assess temporal changes at a given site, given an adequate time series of data, or even using a single dataset, obtained prior to and following enhancement or destruction of a habitat. For example, data from a 13 yr sampling programme (including 29 separate datasets) from the River South Gwash, in Rutland in the English Midlands, indicated a 52% rise in average CCI in the course of a 4 yr programme of eradication of American signal crayfish (Pacifastacus leniusculus) compared with scores obtained prior to their removal. Clearly, factors such as seasonality, maturation of habitat, improvements in identification methods and changes in flow are likely to have an influence on any time series of data. This, in turn, may cause problems in making direct links to a specific conservation strategy. Nevertheless, justification for the strategy can be provided in cases where there are major impacts on a habitat, with CCI indicating subsequent improvements following the implementation of any remedial measures. When applying the CCI, it is important to define what is meant by a ‘site’. Such questions of spatial scale depend on the nature of the study and the desired outcomes. For example, when comparing a range of ponds in a well-defined area such as Orton Brickpits, each pond becomes a ‘site’ and CCI comparison is made between individual ponds in order to draw conclusions on appropriate management practices for the entire SSSI/cSAC. If, on the other hand, all of the ponds at Orton Brickpits were to be compared with a similar set of ponds in a different area, then the entire species list could be amalgamated from each area before undertaking CCI analysis on each of the two resultant datasets. This may then allow a value judgement of the two ‘sites’, defined on a much larger scale, when making decisions relating to statutory designation. Similarly, CCI scores can be compared across a time series of data, as in the example of the River South Gwash. In this case, the ‘site’ is defined as a maximum 50 m stretch, as prescribed by Environment Agency sampling protocols (Murray-Bligh, 1999), and comparison is made between sampling events. Alternatively, it may be necessary to summarize the conservation potential of an entire river or river stretch. In this case, all data obtained from the river in a single year or over a period of years, can be amalgamated so that the whole river, or river stretch, becomes the ‘site’ to which CCI is applied. At scales such as these, however, the use of the BMWP score as a measure of taxon richness becomes progressively less defensible, as the resultant size of the dataset greatly exceeds the conditions under which the original CoS (BMWP) bands were derived. Nevertheless, in such situations, CoS (CSmax) multipliers should still apply. It is, of course, essential that any comparison between CCI scores is made between datasets from ‘sites’ at similar temporal or spatial scales. It would be inappropriate to compare, for example, a single sample from an oligotrophic upland pond with an amalgamated dataset derived from a 10 km downstream reach of a lowland river. Provided this basic tenet is applied, CCI scores should allow sensible conclusions to be

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) 610 R. CHADD AND C. EXTENCE reached. A degree of dissimilarity is allowable, but the more dissimilar the scales or habitats, the greater is the scope for error. CCI thus provides a sound and flexible basis for conservation initiatives, programmes and strategies by producing a summary of aquatic invertebrate data over any appropriate scale of time and space. As well as having been used successfully in a number of important legal submissions, it is also a component of the analytical module of the data storage and processing tool BIOSYS, currently used by the Environment Agency in England and Wales. It is likely to be useful in fulfilling the obligations of British regulatory bodies imposed under the European Economic Community Habitats Directive (EEC, 1992; HMSO, 1994), particularly with regard to formulating management strategies for designated aquatic habitats and for delivering summary information for UK BAPs. It also has a theoretical application under the EC Water Framework Directive (European Commission, 2000), in that it can provide a ready measure of current status, in conservation terms, below which a given site cannot be allowed to fall. It can thus contribute to the overall expression of the condition of an aquatic ecosystem, alongside indices designed to detect flow variation (Extence et al., 1999) or changes in water quality (Chesters, 1980; Extence et al., 1987; Extence and Ferguson, 1989), because it utilizes the same datasets. Therefore, it is an invaluable additional tool in the evaluation and protection of the aquatic environment.

ACKNOWLEDGEMENTS

We are extremely grateful to our colleagues in the Environment Agency for providing data and information, constructive comments and advice; specifically, thanks go to Ian Cappitt, Julie Figures, Alice Hiley and Hannah White at the Spalding Laboratory, and also to Sarah Chadd, Jeanette Collette, Phil Green, Tim Holzer, Ben McFarland, Pete Sibley and Caroline Tero elsewhere. Martin Drake provided invaluable input and a review of the CSs, and useful comments were also received from Ian Wallace, Roger Key, Brian Eversham, Terry Langford, John Redshaw and Tony Cook. Thanks must also be extended to Terry Parr, Co-ordinator of the UK Environmental Change Network at the Centre for Ecology and Hydrology, for permission to use UK ECN data. The views expressed in this paper are our own, and not necessarily those of the Environment Agency.

REFERENCES

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APPENDIX 1: JNCC THREAT CATEGORY DEFINITIONS AND CRITERIA

The threat category definitions and criteria given below are adapted from Wallace (1991).

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Endangered (RDB1)

Taxa in danger of extinction and whose survival is unlikely if the causal factors continue operating. Taxa whose numbers have been reduced to a critical level or whose habitats have been so dramatically reduced that they are deemed to be in immediate danger of extinction. Included are taxa that are known only as a single population in only one 10 km square, taxa that only occur in habitats known to be especially vulnerable, or taxa that have shown a continuous decline over the last 20 yr and now exist in five or fewer 10 km squares.

Vulnerable (RDB2)

Taxa believed likely to move into the Endangered category in the near future. Included are taxa of which most or all of the populations are decreasing because of overexploitation, extensive destruction of habitat or other environmental disturbance; taxa with populations that have been seriously depleted and whose ultimate security is not yet assured; and taxa with populations that may still be abundant but which are under threat from serious adverse factors throughout their range.

Rare (RDB3)

Taxa with small populations, which are not at present Endangered or Vulnerable but which are at risk. These taxa are usually localized within restricted geographical areas or habitats, or are thinly scattered over a more extensive range. Usually, such taxa are not likely to exist in more than 15 10 km squares of the National Grid. This criterion may be relaxed where populations are likely to exist in more than 15 10 km squares but occupy small areas of especially vulnerable habitat.

Notable

Taxa that do not fall within RDB categories 1–3 but which are nonetheless scarce in Great Britain and thought to occur in fewer than 100 10 km squares of the National Grid. For some well-recorded groups of invertebrates (e.g. Coleoptera), Notable has been subdivided into Notable A (30 or fewer 10 km squares) and Notable B (31–100 10 km squares).

Regionally Notable (NR)

Taxa that are too common nationally to fall within the Notable category but which are uncommon in some parts of the country. ‘Uncommon’, in this case, means found in five or fewer localities. The region to which this status applies is described for each species.

Local

Those species not uncommon enough to fall within any of the preceding categories, but which are nonetheless of some interest. A species may qualify, for example, by being very widely distributed but nowhere common, by being restricted to a specialized habitat such as brackish pools but being a common component of this habitat, or simply by being uncommon but not uncommon enough to be Notable. Species with few records but which are suspected of being badly under-recorded are likely to be placed in the Local category. Local species may also be Regionally Notable.

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APPENDIX 2: CONSERVATION SCORES (CS) FOR BRITISH FRESHWATER/BRACKISH WATER INVERTEBRATES

TRICLADIDA Planariidae: Planaria torva 6 Polycelis nigra 1 Polycelis tenuis 1 Polycelis felina 3 Phagocata vitta 3 Crenobia alpina 2 Dugesiidae: Dugesia lugubris 2 Dugesia tigrina 3 Dugesia polychroa 2 Dendrocoelidae: Dendrocoelum lacteum 2 Bdellocephala punctata 7

GASTROPODA Neritidae: Theodoxus fluviatilis 3 Viviparidae: Viviparus viviparus 3 Viviparus contectus 5 Valvatidae: Valvata cristata 2 Valvata macrostoma 9 Valvata piscinalis 1 Hydrobiidae: Hydrobia ventrosa 4 Hydrobia neglecta 6 Hydrobia ulvae 1 Mercuria confusa 10 Potamopyrgus antipodarum 1 Marstoniopsis scholtzi 8 Truncatella subcylindrica 8 Bithyniidae: Bithynia tentaculata 1 Bithynia leachii 5 Assimineidae: Assiminea grayana 2 Paludinella littorina 8 Lymnaeidae: Lymnaea truncatula 3 Lymnaea glabra 9 Lymnaea palustris 2 Lymnaea stagnalis 1 Lymnaea auricularia 2 Lymnaea peregra 1 Myxas glutinosa 10 Physidae: Aplexa hypnorum 5 Physa fontinalis 1 Planorbidae: Planorbarius corneus 4 Menetus dilatatus 7 Planorbis carinatus 1 Planorbis planorbis 1 Anisus vorticulus 9 Anisus vortex 1 Anisus leucostoma 5 Gyraulus laevis 6 Gyraulus albus 1 Gyraulus acronicus 9 Armiger crista 2 Bathyomphalus contortus 2 Hippeutis complanatus 3 Segmentina nitida 10 Acroloxidae: Acroloxus lacustris 2 Ancylidae: Ancylus fluviatilis 1 Succineidae: Succinea oblonga 8 Succinea putris 1 Succinea pfeifferi 1 Succinea elegans 6 Catinella arenaria 10 Vertiginidae: Vertigo antivertigo 3 Vertigo moulinsiana 8 Vertigo lilljeborgi 8 Vertigo angustior 10 Zonitidae: Zonitoides nitidus 4

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BIVALVIA Margaritiferidae: Margaritifera margaritifera 7 Unionidae: Unio pictorum 3 Unio tumidus 5 Anodonta cygnaea 2 Anodonta anatina 3 Pseudanodonta complanata 7 Sphaeriidae: Sphaerium rivicola 3 Sphaerium corneum 1 Sphaerium solidum 10 Musculium lacustre 3 Musculium transversum 5 Pisidium amnicum 3 Pisidium casertanum 1 Pisidium conventus 7 Pisidium personatum 3 Pisidium obtusale 4 Pisidium milium 4 Pisidium pseudosphaerium 8 Pisidium subtruncatum 1 Pisidium supinum 5 Pisidium henslowanum 4 Pisidium lilljeborgii 5 Pisidium hibernicum 4 Pisidium nitidum 3 Pisidium pulchellum 5 Pisidium moitessierianum 4 Pisidium tenuilineatum 8 Dreissenidae: Dreissena polymorpha 2

HIRUDINEA Piscicolidae: Piscicola geometra 2 Glossiphoniidae: Theromyzon tessulatum 2 Hemiclepis marginata 4 Glossiphonia heteroclita 4 Glossiphonia complanata 1 Boreobdella verrucata 7 Haementeria costata 7 Batracobdella paludosa 7 Helobdella stagnalis 1 Hirudinidae: Hirudo medicinalis 8 Haemopis sanguisuga 5 Erpobdellidae: Erpobdella testacea 5 Erpobdella octoculata 1 Dina lineata 6 Trocheta subviridis 4 Trocheta bykowskii 5

ARANEAE Argyroneta aquatica 3

ANOSTRACA Artemia salina 10 Chirocephalus diaphanus 9

NOTOSTRACA Triops cancriformis 10

MALACOSTRACA Bathynellacea: Bathynella natans 7 Bathynella stammeri 7 Mysidacae: Mysis relicta 10 Neomysis integer 1 Isopoda: Asellus aquaticus 1 Asellus cavaticus 7 Asellus communis 7 Asellus meridianus 3 Sphaeroma hookeri 2 Sphaeroma rugicauda 2 Jaera nordmanni 2 Amphipoda: Corophiidae: Corophium curvispinum 3 Corophium arenarium 5 Corophium insidiosum 7 Corophium lacustre 8 Corophium multisetosum 2 Corophium volutator 3

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Crangonyctidae: Crangonyx pseudogracilis 1 Crangonyx subterraneus 7 Melitidae: Allomelita pellucida 7 Gammaridae: Gammarus duebeni 4 Gammarus lacustris 5 Gammarus pulex 1 Gammarus tigrinus 1 Gammarus zaddachi 1 Gammarus insensibilis 8 Echinogammarus berilloni 7 Niphargidae: Niphargus glenniei 7 Niphargus aquilex 6 Niphargus fontanus 7 Niphargus kochianus s.l. 7 Talitridae: Orchestia cavimana 5 Palaeomonidae: Palaemonetes varians 1 Palaemon longirostris 5 Astacidae: Austropotamobius pallipes 7

EPHEMEROPTERA Siphlonuridae: Siphlonurus armatus 6 Siphlonurus lacustris 4 Siphlonurus alternatus 6 Ameletus inopinatus 5 Baetidae: Baetis buceratus 6 Baetis fuscatus 4 Baetis rhodani 1 Baetis scambus 4 Baetis vernus 3 Alainites (Baetis) muticus 2 Labiobaetis (Baetis) atrebatinus 6 Nigrobaetis (Baetis) digitatus 5 Nigrobaetis (Baetis) niger 4 Centroptilum luteolum 4 Cloeon dipterum 1 Cloeon simile 2 Procloeon bifidum 6 Procloeon pennulatum 5 Heptageniidae: Rhithrogena germanica 5 Rhithrogena semicolorata 2 Kageronia (Heptagenia) fuscogrisea 7 Electrogena (Heptagenia) lateralis 2 Heptagenia longicauda 10 Heptagenia sulphurea 4 Ecdyonurus dispar 2 Ecdyonurus insignis 5 Ecdyonurus torrentis 2 Ecdyonurus venosus 2 Arthroplea congener 10 Leptophlebiidae: Leptophlebia marginata 3 Leptophlebia vespertina 3 Paraleptophlebia cincta 3 Paraleptophlebia submarginata 2 Paraleptophlebia werneri 8 Habrophlebia fusca 2 Ephemerellidae: Ephemerella notata 6 Serratella (Ephemerella) ignita 1 Potamanthidae: Potamanthus luteus 9 Ephemeridae: Ephemera danica 1 Ephemera lineata 9 Ephemera vulgata 4 Caenidae: Brachycercus harrisellus 6 Caenis beskidensis 7 Caenis horaria 1 Caenis luctuosa 1 Caenis macrura 4 Caenis pseudorivulorum 6 Caenis pusilla 6 Caenis rivulorum 3 Caenis robusta 5

PLECOPTERA Taeniopterygidae: Taeniopteryx nebulosa 4 Rhabdiopteryx acuminata 7 Brachyptera putata 7 Brachyptera risi 3 Nemouridae: Protonemura praecox 5 Protonemura montana 6 Protonemura meyeri 6 Amphinemura standfussi 6 Amphinemura sulcicollis 2 Nemurella picteti 2

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) CONSERVATION OF FRESHWATER MACROINVERTEBRATE POPULATIONS 617

Nemoura cinerea 1 Nemoura dubitans 7 Nemoura avicularis 4 Nemoura cambrica 2 Nemoura erratica 5 Leuctridae: Leuctra geniculata 4 Leuctra inermis 1 Leuctra hippopus 3 Leuctra nigra 4 Leuctra fusca 1 Leuctra moselyi 6 Capniidae: Capnia bifrons 6 Capnia atra 5 Capnia vidua 7 Perlodidae: Isogenus nubecula 9 Perlodes microcephala 3 Diura bicaudata 3 Isoperla grammatica 2 Isoperla obscura 10 Perlidae: Dinocras cephalotes 4 Perla bipunctata 3 Chloroperlidae: Chloroperla torrentium 1 Chloroperla tripunctata 4 Chloroperla apicalis 10a

ODONATA Platycnemididae: Platycnemis pennipes 5 Coenagriidae: Pyrrhosoma nymphula 3 Ischnura elegans 1 Ischnura pumilio 7 Enallagma cyathigerum 2 Coenagrion armatum 10 Coenagrion hastulatum 9 Coenagrion mercuriale 8 Coenagrion puella 2 Coenagrion pulchellum 5 Coenagrion scitulum 10 Ceriagrion tenellum 6 Erythromma najas 4 Lestidae: Lestes dryas 9 Lestes sponsa 4 Calopterigidae: Calopteryx splendens 2 Calopteryx virgo 5 Gomphidae: Gomphus vulgatissimus 7 Cordulegasteridae: Cordulegaster boltonii 4 Aeshnidae: Brachytron pratense 5 Aeshna caerulea 7 Aeshna cyanea 2 Aeshna grandis 2 Aeshna isosceles 10 Aeshna juncea 4 Aeshna mixta 3 Anax imperator 5 Corduliidae: Cordulia aenea 6 Somatochlora arctica 8 Somatochlora metallica 7 Oxygastra curtisii 10 Libellulidae: Orthetrum cancellatum 5 Orthetrum coerulescens 5 Libellula depressa 5 Libellula fulva 8 Libellula quadrimaculata 4 Sympetrum flaveolum 7 Sympetrum fonscolombii 7 Sympetrum nigrescens 7 Sympetrum sanguineum 5 Sympetrum danae 5 Sympetrum striolatum 1 Sympetrum vulgatum 7 Leucorrhinia dubia 7

HEMIPTERA Mesoveliidae: Mesovelia furcata 6 Hebridae: Hebrus pusillus 7 Hebrus ruficeps 5 Hydrometridae: Hydrometra gracilenta 8 Hydrometra stagnorum 2 Veliidae: Velia caprai 2 Velia saulii 5 Microvelia pygmaea 7 Microvelia reticulata 5 Microvelia buenoi 8

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) 618 R. CHADD AND C. EXTENCE

Gerridae: Gerris costae 4 Gerris lateralis 5 Gerris thoracicus 4 Gerris gibbifer 4 Gerris argentatus 5 Gerris lacustris 1 Gerris odontogaster 2 Aquarius (Gerris) najas 5 Aquarius (Gerris) paludum 7 Limnoporus rufoscutellatus 6 Nepidae: Nepa cinerea 3 Ranatra linearis 5 Naucoridae: Ilyocoris cimicoides 4 Aphelocheiridae: Aphelocheirus aestivalis 5 Notonectidae: Notonecta glauca 1 Notonecta viridis 5 Notonecta obliqua 5 Notonecta maculata 5 Pleidae: Plea minutissima 4 Corixidae: Micronecta scholtzi 6 Micronecta minutissima 8 Micronecta poweri 4 Cymatia bonsdorffi 4 Cymatia coleoptrata 4 Glaenocorisa propinqua 5 Callicorixa praeusta 3 Callicorixa wollastoni 5 Corixa dentipes 5 Corixa punctata 1 Corixa affinis 6 Corixa panzeri 5 Corixa iberica 7 Hesperocorixa linnei 4 Hesperocorixa sahlbergi 2 Hesperocorixa castanea 4 Hesperocorixa moesta 6 Arctocorisa carinata 6 Arctocorisa germari 5 Sigara dorsalis 1 Sigara striata 7 Sigara distincta 3 Sigara falleni 1 Sigara fallenoidea 6 b Sigara fossarum 3 Sigara scotti 5 Sigara lateralis 2 Sigara nigrolineata 2 Sigara concinna 5 Sigara limitata 5 Sigara semistriata 5 Sigara venusta 4 Sigara selecta 6 Sigara stagnalis 5

COLEOPTERA Haliplidae: Brychius elevatus 3 Peltodytes caesus 7 Haliplus apicalis 7 Haliplus confinis 2 Haliplus flavicollis 4 Haliplus fluviatilis 2 Haliplus fulvus 4 Haliplus furcatus 10 Haliplus heydeni 7 Haliplus immaculatus 4 Haliplus laminatus 7 Haliplus lineatocollis 1 Haliplus lineolatus 4 Haliplus mucronatus 8 Haliplus obliquus 4 Haliplus ruficollis 1 Haliplus variegatus 8 Haliplus varius 8 Haliplus wehnckei 3 Hygrobiidae: Hygrobia hermanni 4 Noteridae: Noterus clavicornis 2 Noterus crassicornis 7 Dytiscidae: Laccophilus hyalinus 1 Laccophilus minutus 2 Laccophilus obsoletus 9 Hydrovatus clypealis 8 Hyphydrus ovatus 2 Hydroglyphus geminus 7 Bidessus minutissimus 8 Bidessus unistriatus 10 Hygrotus decoratus 7 Hygrotus inaequalis 2 Hygrotus quinquelineatus 7 Hygrotus versicolor 5 Coelambus confluens 7 Coelambus impressopunctatus 5 Coelambus nigrolineatus 8 Coelambus novemlineatus 7 Coelambus parallelogrammus 7 Hydroporus angustatus 2 Hydroporus discretus 3 Hydroporus elongatulus 8 Hydroporus erythrocephalus 3 Hydroporus ferrugineus 7 Hydroporus glabriusculus 8 Hydroporus gyllenhalii 2 Hydroporus incognitus 3 Hydroporus longicornis 7 Hydroporus longulus 5 Hydroporus marginatus 7 Hydroporus melanarius 5 Hydroporus memnonius 4

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) CONSERVATION OF FRESHWATER MACROINVERTEBRATE POPULATIONS 619

Hydroporus morio 6 Hydroporus neglectus 7 Hydroporus nigrita 3 Hydroporus obscurus 5 Hydroporus obsoletus 7 Hydroporus palustris 1 Hydroporus planus 2 Hydroporus pubescens 2 Hydroporus rufifrons 9 Hydroporus scalesianus 9 Hydroporus striola 2 Hydroporus tessellatus 2 Hydroporus tristis 5 Hydroporus umbrosus 4 Suphrodytes dorsalis 5 Stictonectes lepidus 7 Graptodytes bilineatus 8 Graptodytes flavipes 9 Graptodytes granularis 7 Graptodytes pictus 3 Porhydrus lineatus 6 Deronectes latus 7 Nebrioporus assimilis 5 Nebrioporus depressus 7 Nebrioporus griseostriatus 7 Nebrioporus elegans 1 Stictotarsus duodecimpustulatus 2 Oreodytes alpinus 8 Oreodytes davisii 6 Oreodytes sanmarkii 2 Oreodytes septentrionalis 3 Scarodytes halensis 7 Laccornis oblongus 7 Platambus maculatus 2 Copelatus haemorrhoidalis 3 Agabus affinis 4 Agabus arcticus 6 Agabus biguttatus 7 Agabus bipustulatus 1 Agabus brunneus 9 Agabus chalconatus 7 Agabus congener 5 Agabus conspersus 7 Agabus didymus 1 Agabus guttatus 5 Agabus labiatus 7 Agabus melanarius 7 Agabus melanocornis 5 Agabus nebulosus 1 Agabus paludosus 1 Agabus striolatus 9 Agabus sturmii 1 Agabus uliginosus 7 Agabus undulatus 9 Agabus unguicularis 7 Ilybius aenescens 7 Ilybius ater 3 Ilybius fenestratus 7 Ilybius fuliginosus 1 Ilybius guttiger 7 Ilybius quadriguttatus 5 Ilybius subaeneus 7 Rhantus aberratus 10 Rhantus bistriatus 6 Rhantus exsoletus 5 Rhantus frontalis 7 Rhantus grapii 7 Rhantus suturalis 7 Colymbetes fuscus 1 Hydaticus seminiger 7 Hydaticus transversalis 7 Acilius canaliculatus 7 Acilius sulcatus 5 Graphoderus bilineatus 10 Graphoderus cinereus 8 Graphoderus zonatus 10 Dytiscus circumcinctus 7 Dytiscus circumflexus 7 Dytiscus dimidiatus 7 Dytiscus lapponicus 7 Dytiscus marginalis 1 Dytiscus semisulcatus 4 Gyrinidae: Gyrinus aeratus 7 Gyrinus caspius 3 Gyrinus distinctus 7 Gyrinus marinus 2 Gyrinus minutus 7 Gyrinus opacus 7 Gyrinus paykulli 7 Gyrinus substriatus 1 Gyrinus suffriani 7 Gyrinus urinator 7 Orectochilus villosus 3 Hydrophilidae: Georissus crenulatus 7 Spercheus emarginatus 10 Hydrochus angustatus 7 Hydrochus brevis 8 Hydrochus carinatus 8 Hydrochus elongatus 8 Hydrochus ignicollis 8 Hydrochus megaphallus 8 Hydrochus nitidicollis 8 Helophorus aequalis 1 Helophorus alternans 7 Helophorus arvernicus 7 Helophorus brevipalpis 1 Helophorus dorsalis 8 Helophorus flavipes 2 Helophorus fulgidicollis 7 Helophorus grandis 2 Helophorus granularis 5 Helophorus griseus 7 Helophorus laticollis 9 Helophorus longitarsis 8 Helophorus minutus 3 Helophorus nanus 7 Helophorus nubilus 4 Helophorus obscurus 3 Helophorus strigifrons 7 Helophorus tuberculatus 8 Coelostoma orbiculare 6 Cercyon bifenestratus 8 Cercyon convexiusculus 7 Cercyon depressus 7 Cercyon granarius 8 Cercyon impressus 1 Cercyon lateralis 3 Cercyon littoralis 3 Cercyon lugubris 7 Cercyon marinus 3 Cercyon melanocephalus 2 Cercyon sternalis 7 Cercyon tristis 7 Cercyon ustulatus 7 Paracymus aeneus 10 Paracymus scutellaris 7 Hydrobius fuscipes 1 Limnoxenus niger 7 Anacaena bipustulata 7 Anacaena globulus 1 Anacaena limbata 1 Anacaena lutescens 3 Laccobius atratus 7 Laccobius atrocephalus 7 Laccobius biguttatus 5 Laccobius bipunctatus 2 Laccobius minutus 2 Laccobius obscuratus 10 Laccobius simulator 8 Laccobius sinuatus 7 Laccobius striatulus 2 Helochares lividus 7 Helochares obscurus 8

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) 620 R. CHADD AND C. EXTENCE

Helochares punctatus 7 Enochrus affinis 7 Enochrus bicolor 7 Enochrus coarctatus 7 Enochrus fuscipennis 5 Enochrus halophilus 7 Enochrus isotae 8 Enochrus melanocephalus 7 Enochrus ochropterus 7 Enochrus quadripunctatus 7 Enochrus testaceus 3 Cymbiodyta marginella 5 Chaetarthria seminulum 7 Hydrochara caraboides 10 Hydrophilus piceus 8 Berosus affinis 7 Berosus luridus 7 Berosus signaticollis 7 Berosus spinosus 8 Hydraenidae: Ochthebius aeneus 10 Ochthebius auriculatus 7 Ochthebius bicolon 7 Ochthebius dilatatus 3 Ochthebius exsculptus 7 Ochthebius lenensis 9 Ochthebius marinus 7 Ochthebius minimus 1 Ochthebius nanus 7 Ochthebius poweri 8 Ochthebius punctatus 7 Ochthebius pusillus 7 Ochthebius subinteger 7 Ochthebius viridis 7 Hydraena britteni 5 Hydraena gracilis 1 Hydraena minutissima 7 Hydraena nigrita 7 Hydraena palustris 9 Hydraena pulchella 7 Hydraena pygmaea 8 Hydraena riparia 1 Hydraena rufipes 7 Hydraena testacea 7 Limnebius aluta 7 Limnebius crinifer 8 Limnebius nitidus 7 Limnebius papposus 7 Limnebius truncatellus 1 Elmidae: Elmis aenea 1 Esolus parallelepipedus 4 Limnius volckmari 2 Macronychus quadrituberculatus 8 Normandia nitens 9 Oulimnius major 8 Oulimnius rivularis 7 Oulimnius troglodytes 7 Oulimnius tuberculatus 2 Riolus cupreus 7 Riolus subviolaceus 7 Stenelmis canaliculata 9 Dryopidae: Helichus substriatus 7 Dryops anglicanus 8 Dryops auriculatus 7 Dryops ernesti 3 Dryops griseus 8 Dryops luridus 1 Dryops nitidulus 7 Dryops similaris 7 Dryops striatellus 7 Heteroceridae: Heterocerus fenestratus 3 Heterocerus flexuosus 5 Heterocerus hispidulus 8 Heterocerus obsoletus 3 Chrysomelidae: Donacia aquatica 7 Donacia bicolora 7 Donacia cinerea 7 Donacia clavipes 7 Donacia crassipes 7 Donacia dentata 7 Donacia impressa 7 Donacia marginata 4 Donacia obscura 9 Donacia semicuprea 5 Donacia simplex 5 Donacia sparganii 7 Donacia thalassina 7 Donacia versicolorea 5 Donacia vulgaris 5 Plateumaris affinis 7 Plateumaris braccata 7 Plateumaris discolor 5 Plateumaris sericea 3 Curculionidae: Prasocuris phellandrii 3 Prasocuris junci 5 Tanysphyrus lemnae 5 Eubrychius velutus 7 Litodactylus leucogaster 7 Phytobius canaliculatus 7 Phytobius quadricornis 7 Phytobius quadrinodosus 8 Phytobius quadrituberculatus 5 Gymnetron beccabungae 7 Gymnetron veronicae 7 Poophagus sisymbrii 5 Bagous (Hydronomus) alismatis 7 Scirtidae: Elodes elongata 8 Cyphon pubescens 8 Prionocyphon serricornis 8 Scirtes orbicularis 8

MEGALOPTERA Sialidae: Sialis lutaria 1 Sialis fuliginosa 5 Sialis nigripes 7

NEUROPTERA Osmylidae: Osmylus fulvicephalus 5

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) CONSERVATION OF FRESHWATER MACROINVERTEBRATE POPULATIONS 621

Sisyridae: Sisyra fuscata 5 Sisyra dalii 7 Sisyra terminalis 5

TRICHOPTERA Rhyacophilidae: Rhyacophila dorsalis 1 Rhyacophila septentrionis 7 Rhyacophila obliterata 4 Rhyacophila munda 3 Glossosomatidae: Glossosoma conformis 4 Glossosoma boltoni 3 Glossosoma intermedium 8 Agapetus fuscipes 1 Agapetus ochripes 3 Agapetus delicatulus 3 Philopotamidae: Philopotamus montanus 2 Wormaldia occipitalis 2 Wormaldia mediana 5 Wormaldia subnigra 5 Chimarra marginata 7 Polycentropodidae: Neureclipsis bimaculata 3 Plectrocnemia conspersa 2 Plectrocnemia geniculata 3 Plectrocnemia brevis 8 Polycentropus flavomaculatus 2 Polycentropus irroratus 5 Polycentropus kingi 5 Holocentropus dubius 4 Holocentropus picicornis 3 Holocentropus stagnalis 4 Cyrnus trimaculatus 3 Cyrnus insolutus 10 Cyrnus flavidus 5 Economidae: Ecnomus tenellus 5 Psychomyiidae: Tinodes waeneri 1 Tinodes maclachlani 4 Tinodes assimilis 5 Tinodes pallidulus 9 Tinodes maculicornis 7 Tinodes unicolor 7 Tinodes rostocki 7 Tinodes dives 7 Lype phaeopa 4 Lype reducta 3 Metalype fragilis 7 Psychomyia pusilla 4 Hydropsychidae: Hydropsyche pellucidula 2 Hydropsyche angustipennis 1 Hydropsyche siltalai 1 Hydropsyche saxonica 10 Hydropsyche contubernalis 4 Hydropsyche bulgaromanorum 10 Hydropsyche instabilis 4 Hydropsyche fulvipes 7 Hydropsyche exocellata 10 Cheumatopsyche lepida 4 Diplectrona felix 4 Hydroptilidae: Agraylea multipunctata 1 Agraylea sexmaculata 5 Allotrichia pallicornis 5 Hydroptila sparsa 4 Hydroptila simulans 3 Hydroptila cornuta 7 Hydroptila lotensis 9 Hydroptila angulata 5 Hydroptila sylvestris 7 Hydroptila martini 6 Hydroptila occulta 5 Hydroptila tineoides 2 Hydroptila pulchricornis 6 Hydroptila forcipata 3 Hydroptila vectis 2 Hydroptila tigurina 10c Hydroptila valesiaca 7 Ithytrichia lamellaris 4 Ithytrichia clavata 8 Orthotrichia angustella 5 Orthotrichia tragetti 10 Orthotrichia costalis 5 Oxyethira flavicornis 3 Oxyethira tristella 10d Oxyethira simplex 6 Oxyethira falcata 3 Oxyethira frici 4 Oxyethira distinctella 10 Oxyethira sagittifera 8 Oxyethira mirabilis 8 Tricholeiochiton fagesii 8 Phryganeidae: Hagenella clathrata 10 Phryganea grandis 5 Phryganea bipunctata 2 Oligotricha striata 4 Agrypnia varia 3 Agrypnia obsoleta 5 Agrypnia picta 10e Agrypnia pagetana 5 Agrypnia crassicornis 10 Trichostegia minor 5 Limnephilidae: Ironoquia dubia 9 Apatania wallengreni 5 Apatania auricula 7 Apatania muliebris 5 Drusus annulatus 1 Ecclisopteryx guttulata 4 Limnephilus rhombicus 3 Limnephilus flavicornis 2 Limnephilus subcentralis 7 Limnephilus borealis 7 Limnephilus marmoratus 3 Limnephilus politus 4 Limnephilus tauricus 9 Limnephilus pati 10 Limnephilus stigma 4

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) 622 R. CHADD AND C. EXTENCE

Limnephilus binotatus 5 Limnephilus decipiens 5 Limnephilus lunatus 1 Limnephilus luridus 2 Limnephilus ignavus 6 Limnephilus fuscinervis 7 Limnephilus elegans 7 Limnephilus griseus 4 Limnephilus bipunctatus 5 Limnephilus affinis 3 Limnephilus incisus 3 Limnephilus hirsutus 4 Limnephilus centralis 3 Limnephilus sparsus 2 Limnephilus auricula 3 Limnephilus vittatus 3 Limnephilus nigriceps 6 Limnephilus extricatus 2 Limnephilus fuscicornis 5 Limnephilus coenosus 4 Grammotaulius nitidus 10 Grammotaulius nigropunctatus 4 Glyphotaelius pellucidus 3 Nemotaulius punctatolineatus 8 Anabolia nervosa 2 Phacopteryx brevipennis 7 Rhadicoleptus alpestris 5 Potamophylax latipennis 2 Potamophylax cingulatus 2 Potamophylax rotundipennis 6 Halesus radiatus 2 Halesus digitatus 3 Melampophylax mucoreus 5 Stenophylax permistus 3 Stenophylax vibex 5 Micropterna lateralis 2 Micropterna sequax 1 Mesophylax impunctatus 5 Mesophylax aspersus 8 Allogamus auricollis 4 Hydatophylax infumatus 5 Chaetopteryx villosa 3 Molannidae: Molanna angustata 2 Molanna albicans 5 Beraeidae: Beraea pullata 4 Beraea maurus 3 Ernodes articularis 8 Beraeodes minutus 5 Odontoceridae: Odontocerum albicorne 3 Leptoceridae: Ceraclea albimacula 5 Ceraclea nigronervosa 4 Ceraclea fulva 5 Ceraclea senilis 7 Ceraclea annulicornis 4 Ceraclea dissimilis 3 Athripsodes aterrimus 1 Athripsodes cinereus 1 Athripsodes albifrons 4 Athripsodes bilineatus 5 Athripsodes commutatus 6 Mystacides nigra 6 Mystacides azurea 2 Mystacides longicornis 1 Triaenodes bicolor 2 Ylodes conspersus 7 Ylodes simulans 8 Ylodes reuteri 8 Erotesis baltica 8 Adicella reducta 3 Adicella filicornis 8 Oecetis ochracea 2 Oecetis furva 5 Oecetis lacustris 3 Oecetis notata 8 Oecetis testacea 4 Leptocerus tineiformis 5 Leptocerus lusitanicus 9 Leptocerus interruptus 8 Setodes punctatus 8 Setodes argentipunctellus 8 Goeridae: Goera pilosa 3 Silo pallipes 2 Silo nigricornis 5 Lepidostomatidae: Crunoecia irrorata 3 Lepidostoma hirtum 2 Lasiocephala basalis 6 Brachycentridae: Brachycentrus subnubilus 6 Sericostomatidae: Sericostoma personatum 1 Notidobia ciliaris 6 DIPTERA Tipulidae/Limoniidae/Cylindrotomidae Arctoconopa melampodia 9 Cheilotrichia imbuta 7 Dactylolabis sexmaculata 7 Dactylolabis transversa 7 Dicranota gracilipes 7 Dicranota guerini 7 Dicranota robusta 7 Dicranota simulans 8 Elliptera omissa 10 Erioptera bivittata 9 Erioptera limbata 9 Erioptera meigeni 8 Erioptera meijeri 9 Erioptera neilseni 7 Erioptera nigripalpis 8 Erioptera pusilla 10 Erioptera sordida 8 Gonomyia abbreviata 8 Gonomyia alboscutellata 10 Gonomyia bifida 7 Gonomyia bradleyi 9 Gonomyia connexa 10 Gonomyia conoviensis 7 Gonomyia sexguttata 10 Helius pallirostris 7 Limnophila abdominalis 7 Limnophila apicata 7 Limnophila fasciata 10 Limnophila glabricula 7 Limnophila heterogyna 10 Limnophila mundata 7 Limnophila pictipennis 9 Limnophila pulchella 7

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) CONSERVATION OF FRESHWATER MACROINVERTEBRATE POPULATIONS 623

Limnophila trimaculata 7 Limnophila verralli 7 Limonia aperta 10 Limonia aquosa 7 Limonia bezzii 9 Limonia caledonica 7 Limonia complicata 7 Limonia consimilis 8 Limonia danica 8 Limonia distendens 7 Limonia goritiensis 8 Limonia halterella 7 Limonia lucida 7 Limonia occidua 7 Limonia omissinervis 9 Limonia ornata 7 Limonia rufiventris 8 Limonia stigmatica 7 Limonia stylifera 9 Limonia ventralis 7 Molophilus bihamatus 7 Molophilus corniger 7 Molophilus czizeki 8 Molophilus lackschewitzianus 8 Molophilus niger 7 Molophilus propinquus 7 Neolimnophila carteri 7 Neolimnophila placida 7 Nephrotoma crocata 8 Orimarga juvenilis 7 Orimarga virgo 8 Ormosia aciculata 9 Ormosia bicornis 9 Ormosia staegeriana 7 Paradelphomyia ecalcarata 9 Paradelphomyia fuscula 7 Paradelphomyia nielseni 7 Pedicia lucidipennis 7 Pedicia unicolor 7 Phalacrocera replicata 7 Pilaria fuscipennis 7 Pilaria meridiana 7 Pilaria scutellata 7 Prionocera pubescens 9 Prionocera subserricornis 9 Rhabdomastix hilaris 8 Rhabdomastix inclinata 9 Scleroprocta pentagonalis 8 Scleroprocta sororcula 7 Tasiocera collini 10 Tasiocera fuscescens 10 Tasiocera jenkinsoni 10 Tasiocera laminata 7 Thaumasoptera calceata 7 Tipula bistilata 9 Tipula cheethami 7 Tipula coerulescens 8 Tipula gimmerthali 8 Tipula grisescens 8 Tipula limbata 8 Tipula marginata 8 Tipula serrulifera 10 Tipula siebkei 10 Tipula truncorum 7 Triogma trisulcata 8 Dixidae: Dixa dilatata 5 Dixa maculata 7 Dixa nebulosa 4 Dixa nubilipennis 5 Dixa puberula 5 Dixa submaculata 4 Dixella aestivalis 4 Dixella amphibia 4 Dixella attica 7 Dixella autumnalis 3 Dixella filicornis 7 Dixella graeca 9 Dixella martinii 4 Dixella obscura 7 Dixella serotina 7 Culicidae: Aedes communis 10 Aedes dorsalis 8 Aedes flavescens 9 Aedes leucomelas 10 Aedes stictus 8 Anopheles algeriensis 10 Culiseta longiareolata 10 Orthopodomyia pulcripalpis 8 Thaumaleidae: Thaumalea testacea 6 Thaumalea truncata 8 Thaumalea verralli 6 Ceratopogonidae: Dasyhelea lithotelmatica 9 Simuliidae: Prosimulium hirtipes 5 Prosimulium latimucro 7 Prosimulium tomosvaryi 7 Metacnephia amphora 7 Simulium latipes 6 Simulium angustitarse 6 Simulium lundstromi 4 Simulium armoricanum 5 Simulium cryophilum 4 Simulium juxtacrenobium 6 Simulium urbanum 7 Simulium dunfellense 5 Simulium costatum 5 Simulium angustipes 4 Simulium velutinum 4 Simulium aureum 5 Simulium lineatum 3 Simulium pseudequinum 5 Simulium equinum 2 Simulium erythrocephalum 3 Simulium ornatum 1 Simulium intermedium 5 Simulium trifasciatum 5 Simulium argyreatum 3 Simulium variegatum 4 Simulium tuberosum (sp. complex) 4 Simulium rostratum 6 Simulium morsitans 7 Simulium posticatum 5 Simulium reptans 5 Simulium noelleri 3 Stratiomyidae: Beris clavipes 7 Beris fuscipes 7 Odontomyia angulata 10 Odontomyia argentata 9 Odontomyia hydroleon 10 Odontomyia ornata 9 Odontomyia tigrina 7 Oxycera analis 9 Oxycera dives 8 Oxycera leonina 10 Oxycera morrisii 7 Oxycera pardalina 7 Oxycera pygmaea 7 Oxycera terminata 9 Stratiomys chamaeleon 10 Stratiomys longicornis 9 Stratiomys potamida 7 Vanoyia tenuicornis 7

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004) 624 R. CHADD AND C. EXTENCE

Rhagionidae: Atrichops crassipes 8 Tabanidae: Atylotus plebeius 10 Chrysops sepulcralis 9 Haematopota grandis 8 Tabanus cordiger 7 Tabanus glaucopis 8 Empididae: Chelifera angusta 7 Chelifera aperticauda 7 Chelifera astigma 10 Chelifera concinnicauda 7 Chelifera monostigma 7 Chelifera subangusta 7 Clinocera nivalis 8 Clinocera tenella 8 Clinocera wesmaelii 7 Dolichocephala ocellata 8 Dryodromia testacea 7 Hemerodromia adulatoria 7 Hemerodromia laudatoria 7 Hemerodromia melangyna 9 Stilpon lunata 7 Stilpon sublunata 7 Weidemannia impudica 10 Weidemannia lamellata 10 Weidemannia lota 7 Weidemannia phantasma 8 Dolichopodidae: Acropsilus niger 10 Aphrosylus mitis 8 Campsicnemus compeditus 7 Campsicnemus magius 8 Campsicnemus marginatus 7 Campsicnemus pectinulatus 7 Campsicnemus pusillus 7 Chrysotus monochaetus 7 Chrysotus suavis 7 Dolichopus arbustorum 8 Dolichopus cilifemoratus 9 Hydrophorus viridis 8 Rhaphium fractum 7 Syntormon macula 8 Syntormon filiger 7 Syntormon mikii 9 Syntormon zelleri 7 Systenus bipartitus 8 Systenus leucurus 7 Systenus pallipes 7 Systenus scholtzii 7 Systenus tener 8 Telmaturgus tumidulus 8 Syrphidae: Anasimyia interpuncta 8 Anasimyia lunulata 7 Chrysogaster macquarti 7 Eristalis cryptarum 9 Eristalis rupium 7 Helophilus groenlandicus 9 Lejogaster splendida 7 Lejops vittata 9 Mallota cimbiciformis 7 Orthonevra brevicornis 7 Orthonevra geniculata 7 Parhelophilus consimilis 9 Sciomyzidae: Antichaeta analis 8 Antichaeta brevipennis 9 Colobaea bifasciella 7 Colobaea distincta 7 Colobaea pectoralis 9 Colobaea punctata 7 Dictya umbrarum 7 Pherbellia argyra 9 Pherbellia brunnipes 7 Pherbellia griseola 7 Pherbellia grisescens 7 Pherbellia nana 7 Psacadina vittegera 9 Psacadina zernyi 9 Pteromicra glabricula 7 Pteromicra leucopeza 9 Pteromicra pectorosa 9 Renocera striata 7 Sciomyza dryomyzina 9 Sciomyza simplex 7 Tetanocera freyi 8 Scathophagidae: Acanthocnema glaucescens 7 Acanthocnema nigrimana 8 Muscidae: Lispe caesia 7 Lispe consanguinea 9 Lispe uliginosa 7 Phaonia exoleta 8 aC. apicalis is not yet a confirmed resident species in the UK, but its discovery would warrant RDB status (Bratton, 1990); as a precaution, it has been provisionally assigned a score of 10. bS. fallenoidea is a species currently restricted to Ireland (Savage, 1989), but it may, in time, appear in Great Britain. The species has been given a provisional score of 6. cH. tigurina is known in Britain from a single 1881 record, from Ambleside in the English Lake District (Wallace, 1991). Its score of 10 reflects its likely rarity; it may, however, simply be a highly elusive species. dO. tristella has not been collected in Britain for about 50 yr (Wallace, 1991). The score of 10 is provisional, as its true status is uncertain. eA. picta is known from only two British specimens and is regarded as restricted to the extreme north, but may not be extinct in Britain (Wallace, 1991). It has provisionally been assigned a score of 10 on the basis that, if found, it would be regarded as an extreme rarity in Great Britain. Its status as a British species is regarded as ‘very suspect’ (Wallace et al., 2003).

Copyright # 2004 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 14: 597–624 (2004)