Appendix 8.6 Aquatic Macroinvertebrate Surveys of the Bristol Avon at Conigre Mead and Challymead

Wilts & Berks Canal Trust Environmental Statement Melksham Link canal Appendix 8.6

APPENDIX 8.6 AQUATIC MACROINVERTEBRATE SURVEYS OF THE BRISTOL AVON AT CONIGRE MEAD AND CHALLYMEAD

WBCT/NPA/10653 NICHOLAS PEARSON ASSOCIATES Wilts & Berks Canal Trust Environmental Statement Melksham Link canal Appendix 8.6

WBCT/NPA/10653 NICHOLAS PEARSON ASSOCIATES Aquatic macroinvertebrate surveys of the Bristol Avon at Conigre Mead and Challymead, Melksham.

A survey report by Jon Mellings for Wilts and Berks Canal Trust, 7th May 2015 0

Contents

Summary ...... 2 Introduction ...... 2 Aims and objectives ...... 3 Objectives...... 3 Methods ...... 3 Review of historic records ...... 3 Fieldwork ...... 3 1. Sample sites ...... 3 2. Habitat ...... 4 3. Sampling method ...... 4 4. Washing, sorting and identification of samples ...... 4 Data analysis ...... 4 Results and Discussion ...... 4 Historic records ...... 4 2015 findings ...... 5 5. Habitat ...... 5 6. Macroinvertebrate samples ...... 6 7. Analysis of samples using Biological Monitoring Working Party (BMWP), Average Score Per Taxon (ASPT) and Community Conservation Index (CCI) scores...... 8 Evaluation ...... 9 Habitat and species ...... 9 Survey limitations ...... 10 Survey Conclusions ...... 11 Summary of potential impacts ...... 11 Recommendations ...... 12 References ...... 14 Appendices ...... 15 Appendix 1 - Tables ...... 15 Appendix 2 – Figures ...... 28 Appendix 3– Photographs ...... 29

Summary Freshwater macroinvertebrate surveys were undertaken using standard methods at two sample sites within the Bristol Avon at Melksham, Wiltshire on the 8th April, 2015. The aim of the survey was to inform a planning proposal by the Wilts and Berks Canal Trust to provide a navigable waterway linking the Kennet & Avon Canal at Semington to the river Avon north of Melksham. The scheme proposes the use of a section of the Bristol Avon, currently not used as a navigable waterway.

Two aquatic macroinvertebrate samples were collected at each sample point, namely adjacent to Conigre Mead a non-statutory nature reserve managed by the Wiltshire Wildlife Trust and downstream at Challymead, at a site located south of a proposed weir at the southwest extremity of the proposed navigable section.

In summary both Conigre Mead and Challymead samples were found to support macroinvertebrate samples of ‘Fairly high conservation value’ according to Chadd and Extence (2004) protocol; however, this was based more on species diversity than on rarity of individual species. The recorded habitat and associated macroinvertebrate fauna was characteristic of the Bristol Avon within lowland Wiltshire of a type encompassed within the ‘Rivers, streams and associated habitat’ category defined within the Wiltshire LBAP.

Whilst no specimens were recorded during the survey, the habitat was found to be suitable to support breeding populations of Scarce Chaser Libellula fulva, which has been historically recorded within the survey area.

Whilst a range of aquatic molluscs were recorded from the four samples, Little Whirlpool Ramshorn Anisus vorticulus was not recorded during the survey. This European protected species had formerly been recorded at Conigre Mead Wiltshire Wildlife Trust Reserve; however, it is generally associated with grazing marsh ponds and ditches rather than rivers; therefore its occurrence is more likely to have been found within the ponds at Conigre Mead, or nearby ditches than from the river itself.

A key finding of the survey was the diversity of bottom dwelling caddisfly larvae which require flowing water in which to capture their prey. Whilst no species of especially high rarity value were recorded, significant alterations in flow due to engineering works could impact these and similar species significantly, therefore impacting upon the diversity value of the existing sections.

The report highlights potential impacts likely to result during construction and post-construction operation of the proposed waterway and suggests potential outline recommendations to minimise impact on the site’s macroinvertebrate fauna. As a minimum, the instigation and management of marginal habitat zones and their subsequent management, as well as measures to safeguard habitat downstream of the proposed development are recommended.

Introduction In September 2012, Wilts and Berks Canal Trust submitted a full application for the development of 3.8 km of new waterway running from the Kennet & Avon Canal at Semington to the river Avon north of Melksham. It is understood that the proposed waterway would comprise 3.1 km of new canal plus a 0.7km stretch of the river through the town centre. To enable navigation by boat traffic it is necessary for the summer water level on the stretch to be raised by 0.5m and construction of a small weir at the junction between the River Avon and the Canal has been proposed to facilitate this increase.

Following submission of the planning application, an objection was raised by the wardens of Conigre Mead Wiltshire Wildlife Trust (WWT) Reserve with reference to the potential impact on the riparian diversity of the reserve. Specific concerns relating to the potential impact on the dragonfly and damselfly fauna and other aquatic invertebrate assemblages supported by the stretch of the River Avon passing through the Conigre Mead Reserve and were cited.

In response to the application the County Ecologist and the Environment Agency requested a range of ecological surveys to be carried out including a survey of the aquatic invertebrate fauna of the site.

In April, 2015, Wilts and Berks Canal Trust commissioned Jon Mellings MCIEEM, BSc (hons.) to survey the aquatic macroinvertebrate fauna. The study focused on two sample areas, the first within a 75m stretch of the Bristol Avon immediately to the east of Challymead Bridge at Conigre Mead and the second, immediately downstream of the proposed weir location at Challymead. Note: Sampling within the second section was requested by the Environment Agency (EA).

The following report describes and evaluates findings of freshwater macroinvertebrate survey work conducted on 8th April, 2015 by Jon Mellings MCIEEM, BSc (hons.). Brief suggestions for mitigation are also included within the report.

Aims and objectives The main aim of the survey was to assess the conservation value of the aquatic macroinvertebrate fauna occurring within two stretches of the River Avon at Melksham, Wiltshire. The survey was achieved through completion of the following objectives:

Objectives 1. A brief review of site-specific macroinvertebrate records was undertaken; 2. Macroinvertebrate sampling within a 75 metre stretch of the River Avon adjacent to the banks of the Wiltshire Wildlife Trust managed Conigre Mead Nature Reserve using standard capture techniques and 3. Macroinvertebrate sampling within a stretch of the River Avon immediately downstream of the proposed weir at Challymead was conducted; 4. Macroinvertebrates identified to family and species-level as required for analysis; 5. Data was analysed using Biological Monitoring Working Party (BMWP), Average Score Per Taxon (ASPT) and Community Conservation Index (CCI); 6. Production of a report including findings/species lists, an evaluation of key habitat and species and 7. Provision of brief recommendations re. potential development constraints and mitigation opportunities.

Methods

Review of historic records A review of historic macroinvertebrate records from the survey area was undertaken to inform this report. Sources consulted included protected species listed within a Wiltshire and Swindon Biological Records Centre (WSBRC) data search requested for the purpose of the current project by Oecologic (2013). In addition, a list of species recorded from a macroinvertebrate survey conducted at Conigre Mead on 18th October, 2005 by John Bebbington for Wiltshire Wildlife Trust was kindly supplied by the reserve wardens.

Fieldwork

Sample sites A single site visit was undertaken on 8th April, 2015. Two samples were collected from representative, marginal and in-channel habitat at Conigre Mead and a further two from a meander immediately downstream of the proposed weir at Challymead.

Habitat A summary description of each survey location was recorded, with parameters including 10 figure Ordnance Survey (OS) grid reference (recorded using a handheld Garmin E-trex Global Positioning System), channel substrate, flow characteristics, width and depth of the water column (at the time of survey), evidence of management and main marginal and in-channel macrophyte species and vegetation structure.

Sampling method Each sample was collected and washed in accordance with Murray Bligh (1999) three minute sweep method (as used by the Environment Agency). Effort was made to ensure that each sample was collected from a sufficient range of different, representative meso-habitats to adequately cover the main invertebrate niches of the river section in question. The total sample time per site was timed for three minutes, the sampling time divided between the different meso-habitats and the watch stopped after each sweeping, enabling the contents of the net to be deposited in the sample tray. Kick sampling of the entire river width section was only possible at sample site 4 (Challymead) as the central channel was prohibitively deep within the three remaining sample sites. At these sites, a combination of kick sampling and netting from a fixed position was employed.

Following collection each sample was transferred to a labelled plastic sample pot and preserved using Industrial Methylated Spirit (IMS), in readiness for ex situ washing sorting and identification.

Washing, sorting and identification of samples Each sample was thoroughly washed and graded by rinsing the collected material through a series of standard Endecott sieves. Samples were then sorted into a compartmented plastic sorting square.

The majority of specimens were identified to species level using a binocular microscope. Where necessary specimens were identified using appropriate, up to date taxonomic keys, such as volumes produced by the Freshwater Biological Association and Field Studies Council (FSC).

Data analysis Data was input directly into a spreadsheet set up to calculate BMWP and ASPT scores using Walley and Hawkes, (1997) revised scoring system, CCI scores were also calculated for each sample and interpreted in accordance with Chadd and Extence (2004).

Results and Discussion

Historic records The most significant aquatic macroinvertebrate record for the site is a post 2000 record of the Little Whirlpool Ramshorn Snail Anisus vorticulus, from Conigre Mead. Little Whirlpool Ramshorn is classed as ‘Nationally Vulnerable’ (RDB2) in the UK (pre 1994 IUCN criteria), is listed as a European Protected Species under Annexes 2 and 4 of the Habitats Directive and is included as a ‘Species of Principal Importance’ under Section 41 of the NERC Act (2006).

The record of Little Whirlpool Ramshorn Snail is an outlier in terms of the UK distribution of the species, which is otherwise, largely confined to parts of East Anglia and south-east England.

It is stated in JNCC (2007) that ‘Anisus 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 and Pisidium pseudosphaerium 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

4 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.’

Threats to the species are said to include: ‘Abandonment of pastoral systems; Landfill, land reclamation and drying out, reclamation of land from sea, estuary or marsh; canalisation; other human induced changes in hydraulic conditions, silting, drying out / accumulation of organic material.’(JNCC, 2007).

The precise location of the recorded site for Little Whirlpool Ramshorn Snail at Conigre Mead remains uncertain. It is possible that the mollusc was found in either the ponds on site, the river section, or both. It is also uncertain whether the finding was based on a single specimen or if a population was recorded.

Several records also exist for the Scarce Chaser Libellula fulva which has also been recorded on site. Scarce Chaser is currently classed using post 2001 IUCN guidelines within the ‘Lower Risk – Near Threatened Category’ which has replaced the former RDB3 ‘Nationally Rare’ classification. Whilst Scarce Chaser is not listed within Section 41 of the NERC Act (2006) or previously as a UK Biodiversity Action Plan (UK BAP) species, the insect was afforded LBAP status within the Wiltshire LBAP (2002). Additionally, the habitat within the Bristol Avon was described as being ‘of local importance for its dragonfly and damselfly population,’ with particular reference to Scarce Chaser and White-legged Damselfly Platycnemis pennipes. Such habitat was encompassed within the ‘Rivers, streams and associated habitat’ Wiltshire LBAP classification.

‘The Scarce Chaser is a species of Lowland river floodplains and usually inhabits slow-flowing, meandering rivers and large dykes. Occasionally mature gravel pits and nearby ponds also support populations. Inhabited sites characteristically have good water quality, which supports submerged and floating plants as well as prolific stands of emergent vegetation. Ovipositing females require areas of slow flowing open water, and the adults require some shrub or tree shelter.’ British Dragonflies (accessed 2015).

Site-specific macroinvertebrate data recorded by John Bebbington from Conigre Mead in 2005 included predominately widespread and common species typical of lowland rivers. The most significant species recorded was White-legged Damselfly. This species is local in the UK. In addition, the range of species recorded included taxa including mayflies (Ephemeroptera) and caddisflies (Trichoptera) generally associated with habitats of at least moderately good water quality.

2015 findings

Habitat Habitat descriptions for the four sample site locations (two at Conigre Mead and two at Challymead) are described within Appendix 1, Table 1; sample site locations are indicated on a site map in Appendix 2, Figure 1. A photographic record of each of the sample locations at the time of survey (three photographs of each site) is provide in Appendix 3.

The Bristol Avon flows between around Malmesbury, Wiltshire as far as Avonmouth in the Bristol Channel. The geology of the Bristol Avon catchment within the locality is mainly calcareous. At Melksham, the River flows in a south westerly direction through the town. The Conigre Mead section adjacent to the Conigre Mead Wiltshire Wildlife Trust Reserve, is located towards the southwest boundary of the town, the river flowing outwards through open meadow and arable land in a southwesterly direction. The Challymead section occupies a stretch downstream of Conigre Mead, beyond the on the outskirts of the town. This section is non-canalised and is typical of a lowland river of late stage, being relatively slow flowing and with wide meanders; however, an outflow ditch from the Melksham Sewage Treatment Works flows into the river immediately upstream of the survey section and just downstream of the proposed weir and fish-pass location.

The riverbed was heavily silted within the Conigre Mead section at the time of survey and the wide marginal zones were partially exposed, with a shallow shelf inundated to a depth range of approximately 10 to 30cm, abruptly deepening to approximately 150cm within the channel. The marginal areas were artificially supported by wooded stakes and mesh and attempts had been made to reinstate some natural sinuosity despite the hard engineering. Beneath the silt, a stony substrate including shingle and cobbles was evident.

It is understood that the river section is currently subject to significant (mainly seasonal) water level fluctuations, there was evidence of scour at the margins, especially beneath the A350 Western Way road bridge, located at the southwest, downstream extremity of the Conigre Mead survey area.

The river profile at the two Challymead sample sites was more natural, due to lack of hard engineering and depth range was more variable. Shallow areas were subject to somewhat faster flow, as is typical, and the overall depth was relatively shallow throughout the entire channel and marginal zones, being typically up to about 50cm deep within the main channel, occasionally up to 100cm and with marginal zones ranging from about 0-30cm. The marginal zones were subject to siltation at Challymead, however, gravel and cobbles were present at surface level and sandy exposures were locally present . an alluvial shelf with mature Crack Willow Salix fragilis was present at the opposite (western) bank of the river at Challymead. The channel marginal habitat at Conigre Mead was subject to partial shading from bankside trees, predominately Crack Willow Salix fragilis. Some willows had been recently pollarded as part of the management of Conigre Mead WWT Reserve, enabling light to penetrate the canopy at this point.

At the time of survey the marginal and in-channel vegetation was poorly developed at both Conigre Mead and Challymead, due in part to the time of survey being at the beginning of the growing season. Marginal habitat throughout supported typical riparian species such as Water Forget-me-not Myosotis scorpioides, Reed Canary Grass Phalaris arundinacea, Redshank Persicaria maculosa and Amphibious Bistort P. amphibia. With localised patches of Common Reed Phragmites australis, most notably immediately upstream of the Challymead sample area and Yellow Iris Iris pseudacorus. Emergent Branched Bur-reed Sparganium erectum was generally well represented and within the deeper water of the channel, Yellow Water Lily Nuphar lutea was the most abundant plant. Apparently Arrowhead Sagittaria sagittifolia and Flowering Rush Butomus umbellatus are found at Conigre Mead; these and other aquatic macrophytes would not have been conspicuous due to the time of year.

Macroinvertebrate samples The findings of the macroinvertebrate survey are included in Appendix 1, Tables 2, 3 and 4 below. Table 2 shows a list of all species recorded from all samples together with the UK status and recorded location of each, Table 3 includes complete species data and analysis for the four samples , Table 4 summarises the BMWP and ASPT scores for the four sample sites and Table 5 provides a summary of CCI scores and interpretation categories for each of the samples. Generic explanations of the scoring categories in terms of water quality (BMWP and ASPT) and conservation value (CCI) are provided in Tables 6 and 7 respectively.

A total of 67 macroinvertebrate species were recorded from the four samples collected during the survey. Of these, the most diverse species groups recorded were freshwater snails (Pulmonata) and caddisflies (Trichoptera), with a total of 19 and 16 species respectively recorded for each. Freshwater bivalves comprising pea mussels (Sphaeridae) and freshwater mussels (Unionidae) were relatively well represented within the samples comprising eight species and the larvae of six species of mayfly (Ephemeroptera) were recorded. The remaining orders were represented by few species. Water beetles were particularly poorly represented within the sample data with only a single diving beetle larva (Dytiscidae sp.) being recorded and water bugs (Hemiptera) were completely absent from the samples.

Order Number of species Pulmonata 19 Trichoptera 16 Veneroida 8 Ephemeroptera 6 Hirudinea 4 Diptera 3 Amphipoda 2 Odonata 2 Coleoptera 1 Isopoda 1 Oligochaeta 1 Megaloptera 1 Text figure 1 – number of species recorded per order

Conigre Mead (samples 1 and 2) Macroinvertebrates recorded from the Conigre Mead samples were mainly generalist species typical of the lowland rivers of the region. The species of greater conservation interest included larvae of White-legged Damselfly Platycnemis pennipes, a local species in the UK. White-legged Damselfly is cited alongside Scarce Chaser Libellula fulva, within the Wiltshire LBAP (see historic records section above) and the Bristol Avon is known to support significant populations of both species. Larvae of Scarce Chaser were not recorded however. Brooks and Cham (2014) describe the habitat of White-legged Damselfly as ‘unshaded slow-flowing stretches of rivers and canals with luxuriant floating and emergent vegetation’. Both this species and the more widespread Banded Demoiselle Calopteryx splendens, also recorded in the current survey were also recorded in Bebbington’s (2005) survey.

Another local macroinvertebrate larvae recorded within the Conigre Mead samples was that of the Drake Mackerel Mayfly Ephemera vulgata, one of four mayfly species recorded within the Conigre Mead samples. Drake Mackerel is associated with marginal habitat within muddy rivers (Macadam and Bennett, 2010) and is more restricted in range to the much commoner Green Drake Mayfly E. danica, a typical riparian species, which was also recorded.

Of the 9 caddisflies recorded from Conigre Mead, Polycentropus kingi was the least common species recorded, being widespread but relatively diffusely distributed across the UK. P. kingi was one of six species of the group known of ‘caseless caddis’recorded from the Conigre Mead samples. Larvae of the family Polycentropodidae of which P. kingi is an example, develop on the riverbed in a silken tube which has surfaces onto which prey are trapped. In general, caseless species depend upon river flow or current to capture prey which are swept into the tube or other structure by the current; Polycentropus species favour rivers with relatively slow flow characteristics. However, two species of the family Hydropsychidae including Hydropsyche pellucidula and H. siltalai recorded from the Conigre Mead samples are more typically associated with rivers of somewhat stronger flow characteristics.

Whilst none of the aquatic molluscs recorded were particulaly rare or uncommon, a fairly diverse species assemblage was recorded. Of the aquatic snails, Leach’s Bithynia Bithynia leachii, the Nerite Theodoxus fluviatilis and River Snail Viviparus viviparus are most worthy of note, however, none are especially uncommon in lowland river systems of the region. Whilst several common species of ramshorn snail (Planorbidae) were recorded including the similar, but much commoner Whirlpool Ramshorn Anisus vortex, no specimens conforming to the rare Little Whirlpool Ramshorn A. vorticulus were found in the Conigre Mead samples.

Challymead (samples 3 and 4) There was considerable overlap in species recorded between the Challymead samples and those recorded at Conigre Mead and larvae of the three more local species, White-legged Damselfly Platycnemis pennipes, Drake Mackerel Mayfly Ephemera vulgata and the caseless caddis species Polycentropus kingi, were also recorded at Challymead. Overall, a somewhat higher diversity of caddisfly larvae were recorded from Challymead than at Conigre Mead with 14 species (eight caseless and six cased) were recorded, also a greater number of freshwater molluscs were recorded from Challymead with 18 species of snail and seven species of bivalve (Veneroida).

Of the bivalves recorded, the Hump-backed Pea Mussel Pisidium supinum, recorded alongside commoner species such as Caserta’s Pea Mussel Pisidium casertanum, River Pea Mussel P amnicum and Nut (or River) Orb Mussel Sphaerium rivicola, is a somewhat local species in the UK. Hump-backed Pea Mussel is described in Killeen et al. (2004) as being ‘virtually restricted to large slow-flowing rivers and canals, in clean, calcareous water’.

Two larger freshwater mussels were also recorded from both sections, these included the Duck Mussel Anodonta anatina and Painter’s Mussel Unio pictorum, both species are common and typical of slow flowing lowland rivers.

Analysis of samples using Biological Monitoring Working Party (BMWP), Average Score Per Taxon (ASPT) and Community Conservation Index (CCI) scores.

BMWP and ASPT scores The results of the BMWP, ASPT and CCI analysis for each sample are shown for each sample in turn in Appendix 1, Table3 and summarised in Table 4 (BMWP and ASPT) and Table 5 (CCI).

In terms of BMWP score, three of the samples including both Conigre Mead samples (one and two) and sample three from Challymead exhibited scores which fell between 101-150, indicating ‘good water quality’. The remaining Challymead sample (four), produced a score of 153.4, therefore just edging into the >150 ‘very good water quality’ category. However, the ASPT scores ( simply the average of BMWP scores) calculated for all four samples fell within the >5<6 category indicative of ‘good water quality’. ASPT scores can provide a more reliable measure of water quality as BMWP scores can be inflated by high sample diversity, i.e. where a high diversity of lower scoring families are recorded.

CCI scores The CCI scores calculated from both of the Conigre Mead samples and Challymead sample three, consistently fell towards the lower end of the >10.0 to 15.0 category indicating ‘Fairly high conservation value’ as defined by Chadd and Extence (2004). However, a CCI score of 16 was recorded for Challymead sample 4. According to Chadd and Extence (2004), CCI scores for samples falling between >15.0 and 20.0 indicate sites of ‘High conservation value for their macroinvertebrate fauna.

More than one sample can be bulked to produce an aggregate score for a site using CCI (Chadd and Extence, 2005). A score calculated from combined Conigre Mead samples (one and two), produced a CCI of 11.58, therefore indicating Conigre Mead to support a macroinvertebrate fauna of ‘Fairly high conservation value’. Combined Challymead samples (three and four) produced a site score of 15.58, indicating the site to marginally qualify as being of ‘High conservation value’ based on Chadd and Extence (2004) criteria.

The CCI scoring classifications and description of each classification as used by Chadd and Extence (2004) are Illustrated in Appendix 1, Table 7. It can be seen that the ‘Fairly high conservation value’category is the third highest grouping, described by Chadd and Extence (2004) as ‘Sites supporting at least one uncommon species, or several species of restricted distribution, and /or a community of high taxon richness’. The ‘High conservation value’ category achieved for Challymead sample four and the combined Challymead sites (3 and 4), is descibed as ‘Sites supporting several uncommon species, at least one of which may be nationally rare and/or a community of high taxon richness’. 8

The equation used to calculate a CCI score for a sample or group of samples is based on the sum of the Conservation Scores (CS1) assigned to individual species divided by the number of species in the sample. This is then multiplied by a Community Score (CoS) derived either from the rarest species in the sample or from the highest BMWP score, depending on which is higher. In the case of Melksham samples, one, two and three; the highest CoS for both taxon rarity and based on BMWP score was five. The highest scoring individual species (based on a highest Community Score CS) was five or six depending on the sample site.

For Challymead sample four, the CoS was based on the BMWP rather than highest CS score. The BMWP score of 153.4 just surpassed the lower threshold for the 151-200 category, equating to a CoS score of seven. The high conservation category achieved for sample four can therefore be interpretated as being based on higher sample diversity, rather than on the presence of one or more species of high conservation value being recorded from the sample.

Evaluation

Habitat and species The riparian sections surveyed were typical of the slow-flow, lowland river and associated habitat to be found within Wiltshire. The recorded fauna included species associated with more calcareous substrate and clean water conditions such as the Nerite Theodoxus fluviatilis and Hump-backed Pea Mussel Pisidium supinum. At the time of survey vegetation was not well-developed due to the time of year, but emerging macrophytes recorded included species typical of lowland neutral to calcareous systems. Some shading of the channel by overhanging trees was evident on both sides of the river particularly at Conigre Mead, however, management of willow by pollarding had increased light levels along the bank of the the Conigre Mead Reserve approaching the Western Way road bridge. Efforts to provide habitat varitation at Conigre Mead, by providing marginal ledges had offset the affect of historic canalisation of this section; however, the natural dynamic and sinuosity of the Challymead sections arguably increased the habitat quality in this area, albeit marginally.

Based on the species recorded within the survey; no species classified as a European or UK protected species under instruments such as Annex 2 of the Habitats Directive or Wildlife and Countryside Act (1981) as amended, were recorded; no species listed within Section 41 of the NERC Act (2006) as ‘Species of Prinicipal Importance’ were recorded and none of the species recorded from the 2015 sample data fell within a current higher conservation category including Nationally Scarce (former notable A or B) or were classified as Red Data Book species in the UK either in terms of pre or post 2001 IUCN guidelines.

However, uncommon species including the Scarce Chaser Libellula fulva and Little Whirlpool Ramshorn Anisus vorticulus have been recorded at Conigre Mead Wiltshire Wildlife Trust Reserve post 2000.

In addition to the record centre data for Scarce Chaser, there are anecdotal records of the dragonfly ovipositing within the marginal habitat of Conigre Mead in the past few years, and the Bristol Avon has long been established as a breeding river for this species classed under the IUCN post 2001 ‘Lower-risk – Near Threatened category. Brooks and Cham (2014) describe the breeding habitat of Scarce Chaser as ‘slow-flowing rivers with abundant emergent vegetation, particularly those with associated water meadows and grazing marshes’. Such habitat is comparable with that of the White-legged Damselfly Platycnemis pennipes recorded both historically and during the survey. Whilst at the time of survey the marginal vegetation was not well established, as seen in the photographs (Appendix 3), this

1 CS scores are ascribed in CCI based on known rarity in the UK of individual species within a sample. For example, a CS of 1 or 2 is ascribed to a widespread and common species; 5 or 6 is ascribed in CCI to an individual species which is classed as being of local distribution in the UK and higher CS scores are attributed to classes 7 to 10 and include Nationally Scarce species (CS=7) and Red Data Book species (CS=8-10). 9 was due to the survey time, emergent shoots indicated the presence of well vegetated marginal habitat later in the growing season.

Scarce Chaser Threats include: ‘shading of habitat through uncontrolled growth of marginal trees; over abstraction of water, leading to low-flows, higher water temperatures and deoxygenation; inappropriate river management, such as the removal of fallen trees and weed-cutting; and agricultural and industrial pollution’ (Brooks and Cham, 2014).

The record of Little Ramshorn Snail on site is particularly significant due to the European Protected status. It is unlikely that a record centre such as WSBRC would accept a record for this species without verification from a mollusc expert due to potential confusion with immature Whirlpool Ramshorn Anisus vortex and whilst the record is an outlier in terms of the species’ UK distribution, it must be taken seriously. However, Little Whirlpool Ramshorn is generally a species of ditches and grazing marshes rather than being a riverine species, it is more likely that if this species remains on site, it would be associated with the ponds at Conigre Mead and/or well vegetated ditches and rhynes within the flood meadows as opposed to the river itself.

Whilst the macroinvertebrate fauna collected from the Conigre Mead and Challymead samples in 2015 supported no individual species of significant conservation value, the assemblages recorded contained a relatively high diversity of typical river species. In addition the recorded fauna was representative of good biological water quality in terms of the BMWP and ASPT scores recorded. The greatest diversity of species was recorded from sample four at Challymead. The water level at this sample site was significantly shallower throughout its breadththan was recorded for the other three sample sites. The water depth led to stronger flow characteristics and the higher diversity of species such as caseless caddis larvae which are typically dependent on flow to catch prey within their silken tube nets, is likely to be related to this. Whilst no riffles were present within the sample area, the lower waterlevel and increased flow, are likely to have increased the oxygenation within the water column, increasing the ability of such sections to support species requiring a ready supply of dissolved oxygen.

The greater depth of the central channel at the two Conigre Mead sample sites and the first Challymead site (samples one, two and three), made channel wide kick-sampling impractical, therefore sample coverage may also have influenced the sample findings to some extent.

The species identified from Conigre Mead by Bebbington (2005) supported a similar range of species to those recorded in 2015, with the vast majority of species recorded in 2005 being recorded again in 2015 together with a number of additional species. Certain species ,however, may have not been sufficiently well developed to be apparent within the October sampling event of Bebbington’s survey. Repeat findings of species such as White-legged Damselfly and Banded Demoiselle Calopteryx splendens on site within both 2005 and 2015, suggest that the water and habitat quality between these samples dates has been reasonably consistent, or at least that the river corridor as a whole is sufficiently robust to have allowed continued recolonisation within the section.

Evidence of scour and deposition of flood debris are indicative that of a system subject to considerable seasonal fluctuation and the macroinvertbrate fauna surviving within the site as exisiting are sufficiently robust to survive and in some cases, benefit from these dynamics.

Survey limitations Whilst sampling using standard methods can be viewed as providing a reasonable basis for the evaluation of the conservation value of a site such as Conigre Mead and Challymead, the recorded assemblages cannot be seen as proof that no further species, or no species of higher conservaton persist within the waterbody.

In general terms, spring and autumn are generally considered to be good times to sample macroinvertebrates as larvae of most species such as river flies, which leave the water during the summer are in evidence at these times.

However, certain groups such as water beetles and water bugs for example, are collectively more evident during mid-late summer and poor representation of these groups may be due at least in part to sample time rather than absence.

Survey Conclusions In summary both Conigre Mead and Callymead samples were found to support macroinvertebrate samples of ‘Fairly high conservation value’ according to Chadd and Extence (2004); however, this was based more on species diversity than on rarity of individual species. The recorded habitat and associated macroinvertebrate fauna was charactristic of the Bristol Avon within lowland Wiltshire of a type encompassed within the ‘Rivers, streams and associated habitat’ category defined within the Wiltshire LBAP.

Whilst no specimens were recorded during the survey, the habitat is suitable for supporting breeding populations of Scarce Chaser Libellula fulva, which has been historically recorded within the survey area.

Whilst a range of aquatic molluscs were recorded from the four samples, Little Whirlpool Ramshorn Anisus vorticulus was not recorded during the survey. This European protected species has formerly been recorded at Conigre Mead Wiltshire Wildlife Trust Reserve; however,it is generally associated with grazing marsh ponds and ditches rather than rivers; therefore its occurrence is more likely to have been found within the ponds at Conigre Mead, or nearby ditches than from the river itself.

A key finding of the survey was the diversity of bottom dwelling caddifly larvae which require flowing water in which to capture their prey. Whilst of species of especially high rarity value were recorded, significant alterations in flow due to engineering works could impact these and similar species significantly, therefore impacting upon the diversity value of the existing sections.

Summary of potential impacts Potential impacts on the extant riparian macroinvertebrate fauna from the proposed scheme have been identified as follows:

Conigre Mead

 Changes in water depth and flow characteristics within the survey area of proposed waterway including Conigre Mead. Increased water level would reduce flow and channel depth prohibitive to many riparian macroinvertebrates;  Disturbance through boat traffic due to wash and disturbance of bottom sediment and benthos through use of motorised propellers;  Disturbance to marginal and in-channel vegetation due to boat traffic;  Potential pollution through waste water and grey water from boats and leakage of engine oil and fuel – reduction in water quality through nutrient enrichment and increased toxicity, leading to reduction increased Biological Oxygen Demand (BOD);  Potential transference of invasive species between waterbodies; e.g. Killer Shrimp Dikerogammarus villosus; Zebra Mussel Dreissena polymorpha. Both species are damaging to native fauna.  Discontinuity of habitat corridor and impact on mobility of riverine macroinvertebrates – less mobile macroinverbrates reliant on habitat continuity may be unable to colonise and recolonise adjacent sections of river;  Changes in floodplain dynamics – leading to changes in the dynamics of ditch networks and other habitat;Disposal of rubbish and feeding of ducks etc, impacting upon ecosystem and increasing nutrient enrichment turbidity.

Challymead

 Changes in flow and depth characteristics due to installation and post installation of weir – may adversely impact upon downstream macroinvertebrate assemblages including flow-dependent caddis larvae;  Changes in downstream water quality due to waterway traffic;  Changes in floodplain dynamics – leading to changes in the dynamics of ditch networks and other habitat;  Potential siltation of channel due to suspended sediment – damaging to filter-feeding benthos.

Recommendations The main impacts are likely to be created during and post construction, due to changes in the flow dynamics and depth of the waterbody and potential impact on the ecosystem through wash and sediment disturbancedue to boat traffic. The most damaging potential impacts are likely to include lack of a traversable habitat corridor, for less mobile species to colonise to riparian sections to the north and south of the proposed waterway.

Riverine habitat typically differ significantly from canalised waterways in terms of macroinvertebrate habitat in that rivers typically support mid-channel invertebrate populations which interact with vegetation and may occupy gravel beds and other substrate not typically found in canals. In channel invertebrate assemblages are characteristically poor and the fauna depend largely on well developed marginal habitat.

The survey findings show both the Conigre Mead and downstream Challymead stretches support in-channel invertebrate assemblages, besides the marginal ones with assemblages of caseless and cased caddis being the most significant.

In relation to the river section adjacent to Conigre Mead and throughout the impacted section, provision of sufficiently protected marginal zone adjacent to the navigable channel could provide significant benefit for species associated with vegetated marginal habitat such as dragonflies and damselflies including Scarce Chaser and White- legged Damselfly, certain river-flies, freshwater molluscs, as well as providing more extensive habitat for water beetles and water bugs.

Continuity of habitat within the marginal zones approaching and beneath the Western Way road bridge to the west of Conigre Mead could be provided by provision of an elevated or floating tow path, separating the navigable channel from a vegetated, shallow marginal zone managed as a wildlife corridor. Such a walkway should be designed to allow the movement of water beneath, whilst attenuating excessive wash from waterway traffic.

Measures including a fish-pass in the proposed weir above the lower reaches of the River at Challymead should provide a corridor beneficial for many of the invertebrate species on site, however, water quality attenuation prior to this feature should be considered, to prevent pollutants and excessive siltation occurring downstream. Many benthic invertebrates are filter feeders sensitive to the impacts of siltation. The provision of macrophyte bed filtration systems to attenuate water quality and remove sediments prior to the water being released downstream to Challymead should be considered; however, measures also need to be implemented which would allow, fish and invertebrates to pass downstream with minimal intervention.

Opportunities to manage existing , interconnected waterways including tributary streams and other waterbodies within the Bristol Avon catchment, with a view to provide wildlife corridors beneficial to macroinvertebrates and other wildlife which bypass the proposed navigable waterway at Melksham.

Boat traffic can have a significant impact on bankside and in-channel vegetation, and subsequently on the invertebrate fauna; provision of methods to minimise the impact of boat traffic on vegetation should be considered, including incorporating significant marginal zones with native macrophytes typical of the Bristol Avon (as referred to

12 above); however, strict measures to regulate boat speed should also be instigated. There is a negative relationship between boat speed, size and damage to macrophyte flora and subsequently, macroinvertebrate fauna.

Impact of boat traffic is known to be greater within narrow channels than broader ones, opportunities to widen the channel (but not at the expense of marginal habitat should be considered. Also provision of inaccessible habitat zones mimicking river bed habitat could be considered if possible.

It is expected that statutory requirements limiting the effects of pollution by boat traffic would be incorporated into the design of the waterwayinfrastructure to mitigate potential pollutants entering the watercourse. Such measures should directly limit the impacts on invertebrates through organic pollution, preventing nutrient enrichment and therefore reducing the potential for eutrophication to occur.

Provision for the rapid management and restoration of habitat in the event of waterway related pollution incidents should be considered and a management plan devised to ensure rapid response.

Stringent measures to safeguard all adjacent habitat during and post the construction phase of the project. Particular attention should be paid to minimising the impact of water quality and sediment deposition downstream of the site.

Measures to ensure natural floodplain dynamics are maintained and enhanced for the purpose of nature conservation where possible. Possible creation of mitigation habitat including reinstatement and subsequent management of floodplain wetland habitat including ditches, scrapes and reedbeds adjacent to the River sections at Challymead and beyond could be considered. Such habitat could be of benefit to Little Whirlpool Ramshorn Snail Anisus vorticulus, if the species still occurs in the locality, as well as a wide range of aquatic macroinvertebrates.

A management plan to ensure habitat within the proposed waterway y and adjacent habitat is managed with due sensitivity for invertebrates and other wildlife. The plan should ensure silt within the proposed waterway is dredged sensitively for the benefit of macroinvertebrates and other wildlife. Dredging on rotation should be considered and management of macrophyte beds and bankside vegetation should also be included within a conservation management plan.

Instigate a programme of monitoring2 or at least surveillance within the waterway zone and downstream of the proposed weir at Challymead.

2 For the purpose of this report ‘monitoring’ is taken to mean repeated surveying using a consistant method to enable comparision over a period of time (usually years), where findings are compared with a baseline limit. Monitoring should provide a means of assessing whether a population is being retained in favourable condition or not, therefore nforming conservation management actions. Surveillance is merely a repeated survey, where no limits are set for comparision purposes. 13

References Bebbington, J, 2005, Report on invertebrate taxa found in Bristol Avon at Conigre Mead NR in Melksham 18th October 2005. Unpublished survey report produced for Wiltshire Wildlife Trust.

Brooks, S and Cham, S., 2014. Field guide to the dragonflies and damselflies of Great Britain and Ireland. 5th ed. Oxford: British Wildlife Publishing.

Chadd, R and Extence, C., 2004. The conservation of freshwater Macroinvertebrate populations: a community-based classification scheme.

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.

Killeen, I., Aldridge, D. and Oliver, G., 2004. Freshwater bivalves of Britain and Ireland. 1st ed. Preston Montford: Field Studies Council.

Macadam, C. and Bennett, C, 2010. A pictorial guide to British ephemeroptera. 1st ed. Preston Montford: Field Studies Council.

Murray Bligh, J.A.D. 1999. BT001: Procedures for collecting and analysing Macroinvertebrate samples. Bristol: Environment Agency.

Walley W.J. and Hawkes H.A.,1997. A computer-based development of the Biological Monitoring Working Party score system incorporating abundance rating, biotope type and indicator value. Water Research, 31 (2), 201-210

Appendices

Appendix 1 - Tables

Table 1 – Sample site descriptions

Sample site Sample Sampling Grid reference Habitat Description zone Date 1 Conigre 08/04/2015 ST89803 63738 River section approximately 15m wide at sample point; marginal ledges on east bank Meade approximately 5m wide; margins heavily silted and partially exposed due to low flow at the time of survey; river canalised, but creation of marginal scalloping providing some sinuosity. Flow slow, prevailing flow west. Maximum depth approximately 1.5m; marginal ledges 0-30cm deep. Substrate of margins: Silt over shingle/aggregate (artificially created) boundary of marginal habitat with revetment secured by wooden posts and netting.

Bank with fairly mature Crack Willow Salix fragilis providing partial shade, recently pollarded nearest (A350 - Western Way bridge), immediately west of the sample site. Vegetation not well developed due in part to survey being undertaken early in the growing season. Marginal vegetation included scattered Water Forget-me-not Myosotis scorpioides and Redshank Persicaria maculosa on mud-flats and emergents included Branched Bur- reed Sparganium erectum, Common Reed Phragmites australis, Reed Canary Grass Phalaris arundinacea in shallows. Deeper water with Yellow Water-lily Nuphar lutea. (Note: Arrowhead Sagittaria sagittifolia and Flowering Rush Butomus umbellatus have been recorded, but not seen during survey).

2 Conigre 08/04/2015 ST90081 63862 As sample site 1, but approximately 20 metres upstream. Marginal zone approximately 6m Meade wide and 20-30cm deep; heavily silted and exposed mud poached by dogs, waterbirds and humans. Little marginal or emergent vegetation other than a patch of Yellow Flag Iris Iris pseudacorus close to outer edge of marginal zone and scattered Water Forget-me-not Myosotis scorpioides, Reed Canary Grass Phalaris arundinacea and Redshank Persicaria maculosa also Amphibious Bistort Persicaria amphibia. Yellow Water-lily Nuphar lutea increasingly abundant towards the deeper channel.

Sample site Sample Sampling Grid reference Habitat Description zone Date 3 Challymea 08/04/2015 ST89803 63738 Section similar to Conigre Mead sample site but non-engineered section providing more d natural sinuosity of channel with strong meanders. Samples taken from inner (eastern) bank of meander. Flow: slow-medium; stronger than at Conigre Mead. Western bank with floodplain Crack Willow Salix fragilis marginal zone. Channel approximately 12m wide with marginal zone of approximately 3.5m at sample site, silt and sand over stony bottom. depth of marginal zone approximately 10-20cm, channel 1.5 to 2m. Emergent vegetation predominately Branched Bur-reed Sparganium erectum, with Yellow Water-lily Nuphar lutea in deeper water. Banks steep with tall ruderal vegetation Common Nettle Urtica dioica and bankside Crack Willow Salix fragilis set back from bank, only partially shading channel.

4 Challymea 08/04/2015 ST89801 63743 Approximately 30m upstream of sample site 3. Habitat similar, but river section d approximately 16m wide and gradually deepening from bank to channel, max depth approximately 0.75m. Substrate less silted than sample site 3 and with firm sand and stony bottom towards centre of channel. In channel vegetation predominately Yellow Water-lily Nuphar lutea. Sample taken approximately 20m downstream (west) of proposed weir location. Existing inflow stream from northern bank at the point of proposed weir. Opposite alluvial shelf with Crack Willow Salix fragilis.

Table 2 - Species list of all freshwater Macroinvertebrates recorded during survey

Common name Scientific name Family UK status Sample site

Isopoda (woodlice, slaters and hoglice) 1 2 3 4 A water hoglouse Asellus aquaticus Asellidae Widespread x x x x Amphipoda (freshwater shrimps) A freshwater shrimp Crangonyx Crangonyctidae Widespread x x x pseudogracilis A freshwater shrimp Gammarus pulex Gammaridae Widespread x x x x Freshwater snails (Pulmonata) Lake Limpet Acroloxus lacustris Ancylidae Widespread x x x x River Limpet Ancylus fluviatilis Ancylidae Widespread x x x Leach's Bithynia Bithynia leachii Bithyniidae Widespread x x x Common Bithynia Bithynia tentaculata Bithyniidae Widespread x x x x A terrestrial snail Discus rotundatus Endodontidae Widespread x Dwarf Pond Snail Galba truncatula Lymnaeidae Widespread x Great Pond Snail Lymnaea stagnalis Lymnaeidae Widespread x x x Ear Pond Snail Radix auricularia Lymnaeidae Widespread x x x x Wandering Snail Radix balthica Lymnaeidae Widespread x The nerite Theodoxus fluviatilis Neritidae Widespread x x x An amber snail Physa fontinalis Physidae Widespread x Whirlpool Ramshorn Anisus vortex Planorbidae Widespread Snail x x x x Twisted Ramshorn Bathyomphalus Planorbidae Widespread contortus x White Ramshorn Gyraulus albus Planorbidae Widespread x x x x Ramshorn Planorbis planorbis Planorbidae Widespread x x Jenkins' Spire Shell Potamopyrgus Tateidae Introduced antipodarium (widespread) x x Flat Valve Snail Valvata cristata Valvatidae Widespread x x x Valve Snail Valvata piscinalis Valvatidae Widespread x x River Snail Viviparus viviparus Viviparidae Widespread x x x x Freshwater bivalves (Veneroida) Short-ended Pea Mussel Pisidium subtruncatum Sphaeriidae Widespread x Horny Orb Mussel Sphaerium corneum Sphaeriidae Widespread x x Duck Mussel Anodonta anatina Unionidae Widespread x x x x River Pea Mussel Pisidium amnicum Sphaeriidae Widespread x x x x Caserta Pea Mussel Pisidium casertanum Sphaeriidae Widespread x Hump-backed Pea Mussel Pisidium supinum Sphaeriidae Local x Nut Orb Mussel Sphaerium rivicola Sphaeriidae Widespread x x x Painter's Mussel Unio pictorum Unionidae Widespread x x Segmented worms (Oligochaeta) A segmented worm Oligochaeta spp. Oligochaeta spp. Unknown x x x Leeches (Hirudinea)

Common name Scientific name Family UK status Sample site

A freshwater leech Erpobdella octoculata Erpobdellidae Widespread x x x A freshwater leech Glossiphonia heteroclita Glossiphoniidae Widespread x x x A freshwater leech Helobdella stagnalis Glossiphoniidae Widespread x x A freshwater leech Hemiclepsis marginata Glossiphoniidae Widespread x Ephemeroptera (mayflies) A mayfly Baetidae sp. Baetidae Unknown x Large Dark Olive Baetis rhodani Baetidae Widespread x Medium olive Baetis vernus Baetidae Widespread x Small Spurwing Centrophilum luteolum Baetidae Widespread x x x x An angler's-curse Mayfly Caenis Caenidae Widespread luctuosa/macrura x x x x Green Drake Mayfly Ephemera danica Ephemeridae Widespread x x Drake Mackerel Mayfly Ephemera vulgata Ephemeridae Local x x x Odonata (dragonflies and damselflies) Banded Demoiselle Calopteryx splendens Calopterygidae Widespread x x x x White-legged Damselfly Platycnemis pennipes Platycnemididae Local x x Megaloptera (alderflies) An alderfly Sialis sp. Sialidae Unknown x Caddisflies (Trichoptera) A cased caddis Brachycentrus Brachycentridae Widespread subnubilus x x A caseless caddis Hydropsyche pellucidula Hydropsychidae Widespread x x x A caseless caddis Hydropsyche siltalai Hydropsychidae Widespread x x A cased caddis Ceraclea annulicornis Leptoceridae Widespread x A cased caddis Anabolia nervosa Limnephilidae Widespread x x x A cased caddis Limnephilus lunatus Limnephilidae Widespread x A cased caddis Limnephilus marmoratus Limnephilidae Widespread x A cased caddis Limnephilus rhombicus Limnephilidae Widespread x x A cased caddis Limnephilus sp. Limnephilidae Unknown x A cased caddis Molanna angustata Molannidae Widespread x A caseless caddis Cyrnus trimaculatus Polycentropodidae Widespread x x x A caseless caddis Neureclipsis bimaculata Polycentropodidae Widespread x A caseless caddis Polycentropus Polycentropodidae Widespread flavomaculatus x x x x A caseless caddis Polycentropus kingi Polycentropodidae Local x x x A caseless caddis Lype reducta Psychomyiidae Widespread x A caseless caddis Tinodes waeneri Psychomyiidae Widespread x A cased caddis Sericostoma personatum Sericostomatidae Widespread x Diptera (two-winged flies) A non-biting midge Chironomidae sp. Chironomidae Unknown x x x x A blackfly Simuliidae sp. Simuliidae Unknown x A cranefly Tipulidae sp. Tipulidae Unknown x Coleoptera (beetles)

Common name Scientific name Family UK status Sample site

A diving beetle Dytiscidae sp. Dytiscidae Unknown x

Table 3 –species recorded and BMWP, ASPT and CCI scores per sample site

Sample 1 – Conigre Mead Common name Scientific name Family Order Score Score Stage BMWP CCI A freshwater shrimp Crangonyx Crangonyctidae Amphipoda 1 Adults pseudogracilis A freshwater shrimp Gammarus pulex Gammaridae Amphipoda 4.5 1 Adults A non-biting midge Chironomidae sp. Chironomidae Diptera 3.7 Larvae A cranefly Tipulidae sp. Tipulidae Diptera 5.5 Larvae A mayfly Baetidae sp. Baetidae Ephemeroptera 5.3 Larvae Small Spurwing Centrophilum luteolum Baetidae Ephemeroptera 4 Larvae an angler's-curse Caenis Caenidae Ephemeroptera 7.1 1 Larvae Mayfly luctuosa/macrura Green Drake Mayfly Ephemera danica Ephemeridae Ephemeroptera 9.3 1 Larvae A freshwater leech Erpobdella octoculata Erpobdellidae Hirudinea 2.8 1 Adults A freshwater leech Glossiphonia heteroclita Glossiphoniidae Hirudinea 3.1 4 Adults A freshwater leech Helobdella stagnalis Glossiphoniidae Hirudinea 1 Adults A water hoglouse Asellus aquaticus Asellidae Isopoda 2.1 1 Adults Banded Demoiselle Calopteryx splendens Calopterygidae Odonata 6.4 2 Larvae White-legged Damselfly Platycnemis pennipes Platycnemididae Odonata 5.1 5 Larvae Lake Limpet Acroloxus lacustris Acroloxidae Pulmonata 5.6 2 Adults River Limpet Ancylus fluviatilis Ancylidae Pulmonata 1 Adults Leach's Bithynia Bithynia leachii Bithyniidae Pulmonata 3.9 5 Adults Common Bithynia Bithynia tentaculata Bithyniidae Pulmonata 1 Adults Great Pond Snail Lymnaea stagnalis Lymnaeidae Pulmonata 3 1 Adults Ear Pond Snail Radix auricularia Lymnaeidae Pulmonata 2 Adults The nerite Theodoxus fluviatilis Neritidae Pulmonata 7.5 3 Adults Whirlpool Ramshorn Anisus vortex Planorbidae Pulmonata 2.9 1 Adults Snail White Ramshorn Gyraulus albus Planorbidae Pulmonata 1 Adults Flat Valve Snail Valvata cristata Valvatidae Pulmonata 2.8 2 Adults Valve Snail Valvata piscinalis Valvatidae Pulmonata 1 Adults River Snail Viviparus viviparus Viviparidae Pulmonata 6.3 3 Adults A cased caddis Brachycentrus Brachycentridae Trichoptera 9.4 6 Larvae subnubilus A caseless caddis Hydropsyche siltalai Hydropsychidae Trichoptera 6.6 1 Larvae A cased caddis Anabolia nervosa Limnephilidae Trichoptera 6.9 2 Larvae A cased caddis Limnephilus Limnephilidae Trichoptera 3 Larvae marmoratus A cased caddis Limnephilus sp. Limnephilidae Trichoptera Larvae

A caseless caddis Cyrnus trimaculatus Polycentropodidae Trichoptera 8.6 3 Larvae A caseless caddis Polycentropus Polycentropodidae Trichoptera 2 Larvae flavomaculatus

Sample 1 – Conigre Mead Common name Scientific name Family Order Score Score Stage BMWP CCI A caseless caddis Polycentropus kingi Polycentropodidae Trichoptera 5 Larvae Horny Orb Mussel Sphaerium corneum Sphaeriidae Veneroida 3.6 1 Adults Duck Mussel Anodonta anatina Unionidae Veneroida 5.2 3 Adults River Pea Mussel Pisidium amnicum Sphaeriidae Veneroida 3 Adults Painter's Mussel Unio pictorum Unionidae Veneroida 3 Adults Number of 24 Number 34 scoring BMWP of families: scoring CCI species Total BMWP 127.2 CoS 5 ASPT 5.3 CCI 11.32352941

Sample 2 – Conigre Mead Common name Scientific name Family Order Score Score Stage BMWP CCI Crangonyx A freshwater shrimp pseudogracilis Crangonyctidae Amphipoda 1 Adults A freshwater shrimp Gammarus pulex Gammaridae Amphipoda 4.5 1 Adults A non-biting midge Chironomidae sp. Chironomidae Diptera 3.7 Larvae Ephemeropter 5.3 Small Spurwing Centrophilum luteolum Baetidae a 4 Larvae an angler's-curse Caenis Ephemeropter 7.1 Mayfly luctuosa/macrura Caenidae a 1 Larvae Drake Mackerel Ephemeropter Mayfly Ephemera vulgata Ephemeridae a 9.3 4 Larvae A freshwater leech Erpobdella octoculata Erpobdellidae Hirudinea 2.8 1 Adults A freshwater leech Glossiphonia Glossiphoniidae Hirudinea 3.1 heteroclita 4 Adults A freshwater leech Helobdella stagnalis Glossiphoniidae Hirudinea 1 Adults A water hoglouse Asellus aquaticus Asellidae Isopoda 2.1 1 Adults Banded Demoiselle Calopteryx splendens Calopterygidae Odonata 6.4 2 Larvae A segmented worm Oligochaeta spp. Oligochaeta spp. Oligochaeta 3.5 Adults Lake Limpet Acroloxus lacustris Ancylidae Pulmonata 5.6 2 Adults River Limpet Ancylus fluviatilis Ancylidae Pulmonata 1 Adults Common Bithynia Bithynia tentaculata Bithyniidae Pulmonata 3.9 1 Adults Great Pond Snail Lymnaea stagnalis Lymnaeidae Pulmonata 3 1 Adults Ear Pond Snail Radix auricularia Lymnaeidae Pulmonata 2 Adults Whirlpool Ramshorn Anisus vortex Planorbidae Pulmonata 2.9 1 Adults White Ramshorn Gyraulus albus Planorbidae Pulmonata 1 Adults River Snail Viviparus viviparus Viviparidae Pulmonata 6.3 3 Adults A cased caddis Brachycentrus Brachycentridae Trichoptera subnubilus 9.4 6 Larvae Hydropsyche A caseless caddis pellucidula Hydropsychidae Trichoptera 6.6 2 Larvae A cased caddis Limnephilus rhombicus Limnephilidae Trichoptera 6.9 3 Larvae Polycentropodida A caseless caddis Cyrnus trimaculatus e Trichoptera 8.6 3 Larvae

Sample 2 – Conigre Mead Common name Scientific name Family Order Score Score Stage BMWP CCI

Polycentropus Polycentropodida A caseless caddis flavomaculatus e Trichoptera 2 Larvae Polycentropodida A caseless caddis Polycentropus kingi e Trichoptera 5 Larvae Short-ended Pea Mussel Pisidium subtruncatum Sphaeriidae Veneroida 3.6 1 Adults Horny Orb Mussel Sphaerium corneum Sphaeriidae Veneroida 3.6 1 Adults Duck Mussel Anodonta anatina Unionidae Veneroida 5.2 3 Adults River Pea Mussel Pisidium amnicum Sphaeriidae Veneroida 3 Adults Nut Orb Mussel Sphaerium rivicola Sphaeriidae Veneroida 3 Adults Number of 22 Numbe 29 scoring BMWP r of families: scoring CCI species Total BMWP 113.4 CoS 5 ASPT 5.15454545 CCI 11.0344 5 8

Sample 3 – Challymead Common name Scientific name Family Order Score Score Stage BMWP CCI A freshwater shrimp Gammarus pulex Gammaridae Amphipoda 4.5 1 Adults A non-biting midge Chironomidae sp. Chironomidae Diptera 3.7 Larvae A blackfly Simuliidae sp. Simuliidae Diptera 5.8 Larvae Ephemeropter Small Spurwing Centrophilum luteolum Baetidae a 5.3 4 Larvae An angler's-curse Caenis Ephemeropter 7.1 Mayfly luctuosa/macrura Caenidae a 1 Larvae Ephemeropter Green Drake Mayfly Ephemera danica Ephemeridae a 9.3 1 Larvae Drake Mackerel Ephemeropter Mayfly Ephemera vulgata Ephemeridae a 4 Larvae A water hoglouse Asellus aquaticus Asellidae Isopoda 2.1 1 Adults An alderfly Sialis sp. Sialidae Megaloptera 4.5 Larvae Banded Demoiselle Calopteryx splendens Calopterygidae Odonata 6.4 2 Larvae A segmented worm Oligochaeta spp. Oligochaeta spp. Oligochaeta 3.5 Adults Lake Limpet Acroloxus lacustris Ancylidae Pulmonata 5.6 2 Adults River Limpet Ancylus fluviatilis Ancylidae Pulmonata 1 Adults Leach's Bithynia Bithynia leachii Bithyniidae Pulmonata 3.9 5 Adults Common Bithynia Bithynia tentaculata Bithyniidae Pulmonata 1 Adults Dwarf Pond Snail Galba truncatula Lymnaeidae Pulmonata 3 3 Adults Great Pond Snail Lymnaea stagnalis Lymnaeidae Pulmonata 1 Adults Ear Pond Snail Radix auricularia Lymnaeidae Pulmonata 2 Adults Wandering Snail Radix balthica Lymnaeidae Pulmonata 1 Adults The nerite Theodoxus fluviatilis Neritidae Pulmonata 7.5 3 Adults An amber snail Physa fontinalis Physidae Pulmonata 1.8 1 Adults

Sample 3 – Challymead Common name Scientific name Family Order Score Score Stage BMWP CCI Whirlpool Ramshorn Anisus vortex Planorbidae Pulmonata 2.9 1 Adults Bathyomphalus Twisted Ramshorn contortus Planorbidae Pulmonata 2 Adults White Ramshorn Gyraulus albus Planorbidae Pulmonata 1 Adults Ramshorn Planorbis planorbis Planorbidae Pulmonata 1 Adults Potamopyrgus Jenkins' Spire Shell antipodarium Tateidae Pulmonata 1 Adults Flat Valve Snail Valvata cristata Valvatidae Pulmonata 2.8 2 Adults Valve Snail Valvata piscinalis Valvatidae Pulmonata 1 Adults River Snail Viviparus viviparus Viviparidae Pulmonata 6.3 3 Adults Hydropsyche A caseless caddis pellucidula Hydropsychidae Trichoptera 6.6 2 Larvae A cased caddis Anabolia nervosa Limnephilidae Trichoptera 6.9 2 Larvae A cased caddis Limnephilus rhombicus Limnephilidae Trichoptera 3 Larvae Polycentropus Polycentropodida A caseless caddis flavomaculatus e Trichoptera 8.6 2 Larvae Polycentropodida A caseless caddis Polycentropus kingi e Trichoptera 5 Larvae Duck Mussel Anodonta anatina Unionidae Veneroida 5.2 3 Adults River Pea Mussel Pisidium amnicum Sphaeriidae Veneroida 3.6 3 Adults Nut Orb Mussel Sphaerium rivicola Sphaeriidae Veneroida 3 Adults Number of 23 Numbe 33 scoring BMWP r of families: scoring CCI species Total BMWP 116.9 CoS 5 ASPT 5.082608 CCI 10.454545 7 5

Sample 4 - Challymead Common name Scientific name Family Order Score Score Stage BMWP CCI A freshwater shrimp Crangonyx Crangonyctidae Amphipoda pseudogracilis 1 Adults A freshwater shrimp Gammarus pulex Gammaridae Amphipoda 4.5 1 Adults A diving beetle Dytiscidae sp. Dytiscidae Coleoptera Larva 4.8 e A non-biting midge Chironomidae sp. Chironomidae Diptera Larva 3.7 e Large Dark Olive Baetis rhodani Baetidae Ephemeropter Larva a 5.3 1 e Medium olive Baetis vernus Baetidae Ephemeropter Larva a 3 e Small Spurwing Centrophilum luteolum Baetidae Ephemeropter Larva a 4 e An angler's-curse Mayfly Caenis Caenidae Ephemeropter Larva luctuosa/macrura a 7.1 1 e Drake Mackerel Mayfly Ephemera vulgata Ephemeridae Ephemeropter Larva a 9.3 4 e A freshwater leech Erpobdella octoculata Erpobdellidae Hirudinea 2.8 1 Adults

Sample 4 - Challymead Common name Scientific name Family Order Score Score Stage BMWP CCI A freshwater leech Glossiphonia heteroclita Glossiphoniidae Hirudinea 3.1 4 Adults A freshwater leech Hemiclepsis marginata Glossiphoniidae Hirudinea 4 Adults A water hoglouse Asellus aquaticus Asellidae Isopoda 2.1 1 Adults Banded Demoiselle Calopteryx splendens Calopterygidae Odonata Larva 6.4 2 e White-legged Damselfly Platycnemis pennipes Platycnemididae Odonata Larva 5.1 5 e A segmented worm Oligochaeta spp. Oligochaeta spp. Oligochaeta 3.5 Adults Lake Limpet Acroloxus lacustris Ancylidae Pulmonata 5.6 2 Adults Leach's Bithynia Bithynia leachii Bithyniidae Pulmonata 3.9 5 Adults Common Bithynia Bithynia tentaculata Bithyniidae Pulmonata 1 Adults A terrestrial snail Discus rotundatus Endodontidae Pulmonata Adults Ear Pond Snail Radix auricularia Lymnaeidae Pulmonata 3 2 Adults The nerite Theodoxus fluviatilis Neritidae Pulmonata 7.5 3 Adults Whirlpool Ramshorn Anisus vortex Planorbidae Pulmonata 2.9 1 Adults White Ramshorn Gyraulus albus Planorbidae Pulmonata 1 Adults Ramshorn Planorbis planorbis Planorbidae Pulmonata 1 Adults Jenkins' Spire Shell Potamopyrgus Tateidae Pulmonata 1 antipodarium Adults Flat Valve Snail Valvata cristata Valvatidae Pulmonata 2.8 2 Adults River Snail Viviparus viviparus Viviparidae Pulmonata 6.3 3 Adults A caseless caddis Hydropsyche pellucidula Hydropsychidae Trichoptera 6.6 Larva 2 e A caseless caddis Hydropsyche siltalai Hydropsychidae Trichoptera Larva 1 e Ceraclea annulicornis Leptoceridae Trichoptera 7.8 Larva A cased caddis 4 e 6.9 Larva A cased caddis Anabolia nervosa Limnephilidae Trichoptera 2 e Limnephilus lunatus Limnephilidae Trichoptera Larva A cased caddis 1 e Molanna angustata Molannidae 8.9 Larva A cased caddis Trichoptera 2 e A caseless caddis Cyrnus trimaculatus Polycentropodida Trichoptera 8.6 Larva e 3 e A caseless caddis Neureclipsis bimaculata Polycentropodida Trichoptera Larva e 3 e A caseless caddis Polycentropus Polycentropodida Trichoptera Larva flavomaculatus e 1 e A caseless caddis Lype reducta Psychomyiidae Trichoptera Larva 6.9 3 e A caseless caddis Tinodes waeneri Psychomyiidae Trichoptera Larva 1 e Sericostoma Sericostomatidae Trichoptera Larva A cased caddis personatum 9.2 1 e Duck Mussel Anodonta anatina Unionidae Veneroida 5.2 3 Adults River Pea Mussel Pisidium amnicum Sphaeriidae Veneroida 3 Adults Caserta Pea Mussel Pisidium casertanum Sphaeriidae Veneroida 1 Adults Hump-backed Pea Pisidium supinum Sphaeriidae Veneroida 3.6 Adults Mussel 5 Nut Orb Mussel Sphaerium rivicola Sphaeriidae Veneroida 3 Adults

Sample 4 - Challymead Common name Scientific name Family Order Score Score Stage BMWP CCI Painter's Mussel Unio pictorum Unionidae Veneroida 3 Adults Number of 28 Numbe 42 scoring BMWP r of families: scoring CCI species Total BMWP 153.4 CoS 7 ASPT 5.47857142 CCI 9 16

Table 4 – Summary of BMWP and ASPT scores per sample site

Sample Sample zone BMWP Score Category ASPT score Category Water quality number classification

1 Conigre Mead 127.2 101-150 5.3 >5 <6 Good 2 Conigre Mead 113.4 101-150 5.15 >5 <6 Good 3 Challymead 116.9 101-150 5.08 >5 <6 Good 4 Challymead 153.4 >150 5.48 >5 <6 Good/very good

Table 5 – Summary of CCI scores per sample site and combined sample sites

Sample site Sample CCI Score Scoring category Conservation CCI interpretation number Category Conigre Mead 1 11.32 Fairly high Sites supporting at least one uncommon species, or several species of >10.0 – 15.0 conservation restricted distribution, and /or a community of high taxon richness value Conigre Mead 2 11.03 Fairly high Sites supporting at least one uncommon species, or several species of >10.0 – 15.0 conservation restricted distribution, and /or a community of high taxon richness value Challymead 3 10.45 Fairly high Sites supporting at least one uncommon species, or several species of >10.0 – 15.0 conservation restricted distribution, and /or a community of high taxon richness value Challymead 4 16 High Site supporting several uncommon species, at least one of which may >15.0 – 20.0 conservation be nationally rare and/or a community of high taxon richness value Conigre Mead 1 and 2 11.54 Fairly high combined Sites supporting at least one uncommon species, or several species of >10.0 – 15.0 conservation restricted distribution, and /or a community of high taxon richness value

Challymead 3 and 4 15.58 High Site supporting several uncommon species, at least one of which may combined >15.0 – 20.0 conservation be nationally rare and/or a community of high taxon richness value

Table 6 –Explanation of BMWP and ASPT categories

BMWP and ASPT score interpretration

BMWP score ASPT score Water quality classification >150 >6 Very Good 101-150 >5 Good 51 - 100 >4 Moderate 16-50 <4 Poor 0-15 Very Poor

Table 7 – Explanation of CCI score categories

CCI Score Conservation Category Interpretation

0.0 – 5.0 Low conservation value Sites supporting only common species and/or a community of low taxon richness

>5.0 – Moderate conservation value Sites supporting at least one species of restricted distribution and/or a community of 10.0 moderate taxon richness

>10.0 – Fairly high conservation value Sites supporting at least one uncommon species, or several species of restricted distribution, 15.0 and /or a community of high taxon richness

>15.0 – High conservation value Site supporting several uncommon species, at least one of which may be nationally rare 20.0 and/or a community of high taxon richness

>20.0 Very high conservation value Sites supporting several rarities, including species of national importance, or at last one extreme rarity(e.g. taxa included in the British RDBs) and/or a community of very high taxon richness

Appendix 2 – Figures

Figure 1 – Macroinvertebrate sample sites 8/4/2015

Appendix 3– Photographs

Photograph 1 – Sample site 1 Conigre Mead showing exposed Photograph 2 – Sample site 1 Conigre Mead showing exposed Photograph 3– Sample site 1 Conigre Mead looking upstream marginal habitat marginal habitat and scour beneath bridge

Photograph 4 – Sample site 2 Conigre Mead showing poaching and Photograph 5 – Sample site 2 Conigre Mead Photograph 6 – Sample site 2 Conigre Mead in-channel Iris pseudacorus stand

Photograph 7 – Sample site 3 Challymead Photograph 8 – Sample site 3 Challymead Photograph 9 – Sample site 3 Challymead showing regenerating emergent vegetation

Photograph 10 – Sample site 4 Challymead Photograph 11 – Sample site 4 Challymead showing emergent Photograph 12 – Sample site 4 Challymead showing reedbed vegetation immediately upstream of proposed weir