Aquatic Macro-invertebrate Sampling at three sites on the Lower Duke of Northumberland s River; October 13 th 2015:

Transcription

1 Photos Ilse Steyl Aquatic Macro-invertebrate Sampling at three sites on the Lower Duke of Northumberland s River; October 13 th 2015: WHPT Analysis and Preliminary Species Audit Report V_1.0 Conducted by: John Dobson BSc MSc MCIEEM FRES Make Natural Ltd (Ecological Services) contact@makenatural.co.uk For: Green Corridor

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3 Aquatic Macro-invertebrate Sampling at three sites on the Lower Duke of Northumberland s River; October 13 th 2015: WHPT Analysis and Preliminary Species Audit Report V_1.0 Conducted by: John Dobson BSc MSc MCIEEM FRES Make Natural Ltd (Ecological Services) contact@makenatural.co.uk For: Green Corridor CONTENTS 1. EXECUTIVE SUMMARY BACKGROUND METHODS... 2 Table 1. Locations of the selected Sampling Areas on the DNR, 13 October LIMITATIONS OF SURVEY RESULTS... 5 Table 2: WHPT analysis for the three sampling sites Table 3: Species Date from the WHPT Survey of the DNR, 13 October DISCUSSION... 8 Species Accounts RECOMMENDATIONS REFERENCES & BIBLIOGRAPHY Appendix 1: Map showing locations of the Sampling Areas Appendix 2: Photographs Appendix 3: Risk Assessment... 17

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5 1. EXECUTIVE SUMMARY Make Natural Ltd. (Ecological Services) sampled aquatic invertebrates from three sites on the Lower Duke of Northumberland s River for Green Corridor on 13 October The aims of the survey were to monitor the water quality using WHPT in respect of anticipated river corridor improvement works, and to make a preliminary inventory of the species present. 26 Families/higher taxa were recorded for WHPT analysis, including a number of moderately high scoring families (indicating moderately high water quality). No highly pollution intolerant families (which would indicate high water quality) were recorded. Of the 35 recorded species, none has a statutory conservation status or are nationally scarce or rare. Two species are highlighted as being Local or Very Local in Greater London. One designated invasive species (Schedule 9, W&C Act 1981) was recorded. 2. BACKGROUND Make Natural Ltd. (Ecological Services) was contracted by Green Corridor (Steyning, West Sussex) to sample, identify and analyse aquatic macro-invertebrates at three locations on the Lower Duke of Northumberland s River (DNR) where it runs through the London Boroughs of Hounslow and Richmond upon Thames. The River is designated as a Site of Borough Importance for Nature Conservation grade 1 in both boroughs. The survey was carried out on 13 October 2015 by John Dobson (JRD)(Make Natural Ltd.) accompanied for survey area selection and for health and safety purposes by Dr. Ilse Steyl (IS) (Crane Valley Partnership Development Manager, Green Corridor), and for part of the survey by Gareth Ryman (Biodiversity Officer, London Borough of Hounslow). Aims of the Survey 1. To sample aquatic macro-invertebrates following standard methodology and to analyse those samples utilising invertebrate families as indicators of the organic pollutant load and general degradation occurring at the sampling sites. 2. To identify the sampled aquatic macro-invertebrates to species level. 1

6 3. METHODS WHPT Sampling and data analysis were conducted according to WHPT (Walley, Hawkes, Paisley & Trigg) methodology (Environment Agency, 2012) (but see Limitations of Survey p. 4). Note on WHPT: WHPT is the current revision of the superseded BMWP (Biological Monitoring Working Party) scoring system for assessing organic pollutants and General Degradation in watercourses on the basis of macro-invertebrate sampling (Chadd, 2010). Key differences between WHPT and BMWP are: i. In WHPT the score applied to each taxon is based on extensive research and sampling data (The development of BMWP scores was committee based). The list of scoring taxa is more extensive than the BMWP list, due both to the inclusion of additional taxa and splitting of some BMWP species aggregates. ii. WHPT scoring utilises abundance data rather than presence/absence as in BMWP. In addition to providing additional ecological information this refinement meets Water Framework Directive (WFD) criteria. Field Procedures Three survey areas of the DNR were nominated by IS. At each survey areas the sampling area was selected by JRD on the basis of typicality (Environment Agency, 2012) and safe access, and these locations are set out in Table 1. Although not within the WHPT protocol, some contextual data was collected at each sampling point; these are the watercourse dimensions and flow rate (a floating object timed 3-5x over a 3m stretch). This data and the calculated discharge rates (Q) are included in Table 1. At each location sampling was performed within a sampling area 10m up- and downstream of the access point, using a standard (250mm frame, 1mm mesh) sampling net. A timed 3 minutes was spent kick-sampling working diagonally upstream over the full width of the river. The sampling time was divided proportionally between the major mesohabitats present, particularly silt and fine gravel substrates, and emergent and submerged vegetation. An additional 1 minute was spent sampling mesohabitats which were under-sampled by kick-sampling. These included: among the roots of emergent vegetation, beneath large stones and the vertical faces of banks. The net was washed with river water and inspected for carry-over between each of the three survey areas. Each of the three samples was transferred to a 5l lidded bucket which was transported off-site on ice in order to minimise predation and degradation within the samples. Risk Assessment: See Appendix 3, p. 17. Biosecurity: Nets, footwear and containers were cleaned and treated before and after the survey with Safe4Pets, which has proven efficacy against Ranavirus and Chytridiomycosis fungus. Table 1. Locations of the selected Sampling Areas on the DNR, 13 October 2015 Grid Ref Location Name Depth Mean Q Width cm depth cm Flow rate m d¼+d½+d¾ m.s -1 Discharge ¼ ½ ¾ 3 rate m 3.s -1 Site 1 downstream TQ Nr. Riverside Walk Site 2 TQ S. of Whitton Dene Site 3 upstream TQ Rosecroft Gardens [N.B. The discharge rate for Site 1 appears anomalous, and it may be that the flow rate at the measured 3m stretch was unrepresentative.] 2

7 Sample Processing Sample Sorting Large material such as stones and vegetation was removed from the samples manually and washed and examined to extract macro-invertebrates. Each sample was then passed through a 500μ sieve and the retained material examined in detail. Leeches (Hirudinea) and flatworms (Tricladida) were removed live (to facilitate identification) and tubed individually. The samples were then dosed with ethyl acetate in order to kill the remaining invertebrates. The entire samples were then preserved in 70% iso-propyl alcohol (IPA) and subsequently transferred in small aliquots to white trays for further examination. Preliminary sorting of macro-invertebrates was carried out using a magnifying headset in conjunction with supplementary illumination. Specimens were removed from the samples and tubed in 70% IPA according to Order or Family as appropriate. Due to the large numbers of Gammaridae present in samples 1 and 3, 50% of the samples were examined in detail and the results multiplied by 2 (Davy-Bowker, 2015). The preserved samples of Gammaridae were spread evenly across the surface of a large white tray which had been marked-up with ruled lines. Gammaridae lying in 50% of the overall area were selected for subsequent examination. All Gammaridae present in samples 2 were examined. Identification Specimens were examined using a Bausch & Lomb (7-60x) stereozoom microscope and, where higher magnification was required, a Leitz Laborlux 12 binocular microscope. Various illumination sources were used including an LED ring-light and a Schott fibre optic light source. Specimens were identified to family and species utilising the appropriate keys (see References & Bibliography, p. 13). Leeches (Hirudinea) and flatworms (Tricladida) were identified live (to facilitate identification of most species) although subsequently killed where dissection was required to resolve critical taxa. The remaining preserved specimens were identified to the taxonomic level appropriate to WHPT and the project brief (see Limitations of Survey, Page 4). The resulting data was added to a spreadsheet together with the full biological records. The spreadsheet (Lower DNR Invertebrate species Data MNP0255.xlxs) is included with this report. Voucher material preserved in IPA will be retained for one year from the date of the survey. 3

8 4. LIMITATIONS OF SURVEY Modifications to protocol. (i) WHPT analysis requires at least two annual samples, normally taken in spring and autumn (Environment Agency, 2012). At the DNR in 2015 a single autumn sampling was carried out. The full WHPT procedure was therefore not completed in 2015 and the results for that year are therefore not WFD compliant in that respect. (ii) In the standard methodology (Environment Agency, 2012) thirty seconds of the sampling period (total 4 minutes) is spent sampling surface-dwelling macro-invertebrates such as whirligig beetles (Coleoptera, Gyrinidae) and pond skaters (Heteroptera, Gerridae). No examples of surface-dwelling fauna were observed at any stage and therefore that thirty seconds was utilised as additional time sampling other habitats which are normally under-sampled by kick-sampling, such as among the roots of emergent vegetation and the vertical faces of banks. Interpretation of Data. A variety of water quality metrics are publicly accessible via the Environment Agency Catchment Data Explorer (see References and Bibliography p. 13). Data is available from this source for the River Crane and for the Duke of Northumberland s River near Heathrow but not for the Lower DNR, the subject of this survey. In addition, no WHPT or BMWP data is included. WHPT scores benchmark all rivers against data obtained from the best quality (unmodified and unpolluted) examples available. In the absence of available HWPT scores from comparable urban rivers in south-east England, it is not possible at this stage to benchmark the Lower Duke of Northumberland s River against other watercourses of its kind. Identification of Taxa. Not all taxa are identifiable beyond the level required for WHPT. For example it not currently possible to identify most fly (Diptera) and beetle (Coleoptera) larvae to species, whilst identification of other groups such as Pisidium molluscs (Mollusca, Sphaeriidae) and freshwater mites (Araneae, Acari) requires sub-specialist input. Early instar riverfly larvae may be identifiable to family but not to species; and damaged specimens of all taxa may also limit the scope for identification. The number of specimens identified to species is therefore normally expected to be significantly lower than the number of specimens identified to family. 4

9 5. RESULTS WHPT analysis: The WHPT analysis for the three sampling sites is set out in Table 2. Table 2: WHPT analysis for the three sampling sites. Families are listed in taxonomic order. Order/Higher Taxon Family No. Site 1 Site 2 Site 3 WHPT index value No. WHPT index value Tricladida (flatworms) Planariidae Mollusca (snails, limpets and mussels) Physidae No. WHPT index value Bithyniidae Hydrobiidae Lymnaeidae Planorbidae Sphaeriidae Oligochaeta (segmented worms) NA* Hirudinea (leeches) Glossiphoniidae Erpobdellidae Crustacea (crayfish, slaters and shrimps) Astacidae Asellidae Gammaridae Ephemeroptera (mayflies) Baetidae Caenidae Odonata Zygoptera (damselflies) Calopterygidae Coleoptera (beetles) Elmidae Neuroptera (lacewings - sponge flies) Sisyridae Trichoptera (caddisflies) Glossosomatidae Hydropsychidae Limnephilidae Molannidae Leptoceridae Diptera (true flies) Dixidae Chironomidae Stratiomyidae N-Taxa WHPT-ASPT Total WHPT Abbreviations N-Taxa: Number of Taxa ASPT: Average Score per Taxon WHPT: Walley, Hawkes, Paisley & Trigg scores (Environment Agency, 2012) * [Note that Oligochaeta (segmented worms) are scored under WHPT as a Subclass (Oligochaeta) rather than as Families.] 5

10 Species Data: Species records derived from the survey are summarised in Table 3, and appear in full on the accompanying spreadsheet. Notes on Table 3 All species were captured by kick-sampling on 13 October 2015 by J. R. Dobson and subsequently identified by J. R. Dobson. The locations of the sampling areas on the Duke of Northumberland s River (DNR 1, 2 & 3) appear in Table 1, p. 2, and in the Map on p. 15. The column headed No. identified (No. present) shows the number of specimens identified to species followed by, in brackets, the number of specimens belonging to the appropriate higher taxa which were counted. Specimens which were too immature or damaged were excluded from species identification. Records of Genus juvenile ident. are included only where no species records for the genus are available from the sampling area. Table 3: Species Date from the WHPT Survey of the DNR, 13 October 2015 Family Species Vernacular name No. identified (No. present) Larva/ Adult Location Dugesiidae Dugesia lugubris Flatworm 1 A DNR 2 Planariidae Polycelis tenuis Flatworm 1 A DNR 2 nd Nematoda sp. Roundworm 0 (1) nd DNR 1 nd Nematoda sp. Roundworm 0 (19) nd DNR 2 nd Nematoda sp. Roundworm 0 (1) nd DNR 3 Erpobdellidae Erpobdella octoculata Leech 2 A DNR 1 Erpobdellidae Erpobdella octoculata Leech 5 A DNR 2 Glossiphoniidae Glossiphonia complanata Leech 1 A DNR 2 Glossiphoniidae Glossiphonia complanata Leech 1 A DNR 3 Glossiphoniidae Glossiphoniidae sp. juv. Ident. Leech 1 A DNR 1 Glossiphoniidae Helobdella stagnalis Leech 1 A DNR 3 Glossiphoniidae Theromyzon tessulatum Leech 2 A DNR 2 nd Oligochaeta spp. Segmented worm 0 (5) nd DNR 1 nd Oligochaeta spp. Segmented worm 0 (3) nd DNR 2 nd Oligochaeta spp. Segmented worm 0 (14) nd DNR 3 Bithyniidae Bithynia tentaculata Common bithynia 4 A DNR 1 Lymnaeidae Lymnaea stagnalis Great pond snail 1 A DNR 2 Lymnaeidae Radix balthica Wandering snail 1 A DNR 2 Physidae Physa fontinalis Common bladder snail 1 A DNR 1 Planorbidae Ancylus fluviatilis River limpet 1 A DNR 2 Planorbidae Planorbarius corneus Great ramshorn 1 A DNR 2 Planorbidae Planorbis planorbis/carinatus Margined/Keeled ramshorn 6 A DNR 2 Planorbidae Planorbis planorbis/carinatus Margined/Keeled ramshorn 1 A DNR 3 Sphaeriidae Pisidium spp. A Pea mussel 2 nd DNR 1 Sphaeriidae Pisidium spp. A Pea mussel 1 nd DNR 3 Sphaeriidae Sphaerium corneum Horny orb mussel 13 nd DNR 1 Sphaeriidae Sphaerium corneum Horny orb mussel 9 nd DNR 2 Sphaeriidae Sphaerium corneum Horny orb mussel 14 nd DNR 3 Tateidae Potamopyrgus antipodarum Jenkins' spire snail 1 A DNR 3 Hydrachnidae nd Freshwater Mites 0 (1) A DNR 1 Hydrachnidae nd Freshwater Mites 0 (6) A DNR 2 6

11 Table 3: Species Date from the WHPT Survey of the DNR, 13 October 2015 (continued) Family Species Vernacular name No. identified (No. present) Larva/ Adult Location Asellidae Asellus aquaticus Water hoglouse or -slater 6 A DNR 1 Asellidae Asellus aquaticus Water hoglouse or -slater 6 (19) A DNR 2 Asellidae Asellus aquaticus Water hoglouse or -slater 1 A DNR 3 Gammaridae Gammarus pulex A freshwater shrimp 15 (214) A DNR 1 Gammaridae Gammarus pulex A freshwater shrimp 9 (57) A DNR 2 Gammaridae Gammarus pulex A freshwater shrimp 12 (198) A DNR 3 Astacidae Pacifastacus leniusculus Signal Crayfish 1 A DNR 3 Sisyridae Sisyra sp. A sponge fly 0 (2) L DNR 3 Baetidae Baetis rhodani Large Dark Olive 6 (>10) L DNR 1 Baetidae Baetis rhodani Large Dark Olive 5 (54) L DNR 3 Caenidae Caenis horaria Anglers curse 1 L DNR 1 Caenidae Caenis horaria Anglers curse 3 (3) L DNR 3 Calopterygidae Calopteryx sp. juv. ident. A Demoiselle 1 L DNR 1 Calopterygidae Calopteryx splendens Banded demoiselle 8 (16) L DNR 2 Glossosomatidae Agapetus fuscipes A Caddis fly 4 (10) L DNR 1 Glossosomatidae Agapetus fuscipes A Caddis fly 1 (14) L DNR 3 Hydropsychidae Hydropsyche angustipennis A Caddis fly 8 (>10) L DNR 1 Hydropsychidae Hydropsyche angustipennis A Caddis fly 5 L DNR 2 Hydropsychidae Hydropsyche angustipennis A Caddis fly 6 (15) L DNR 3 Hydropsychidae Hydropsyche pellucidula A Caddis fly 3 L DNR 2 Leptoceridae Athripsodes cinereus A Caddis fly 1 L DNR 1 Leptoceridae Mystacides azurea A Caddis fly 1 L DNR 3 Limnephilidae Limnephilidae sp. juv. ident. A Caddis fly 0 (1) L DNR 2 Molannidae Molanna angustata A Caddis fly 2 L DNR 2 Molannidae Molanna angustata A Caddis fly 1 L DNR 3 Elmidae Elmis aenea A Riffle beetle 1 A DNR 1 Elmidae Elmis aenea A Riffle beetle 1 A DNR 3 Elmidae Oulimnius tuberculatus A Riffle beetle 1 A DNR 3 Chironomidae Subfamily Orthocladinae Non-biting midge 3 L DNR 2 Chironomidae Subfamily Chironominae Non-biting midge 4 L DNR 2 Chironomidae Subfamily Chironominae Non-biting midge 2 L DNR 1 Chironomidae Subfamily Chironominae Non-biting midge 4 L DNR 3 Chironomidae Subfamily Orthocladinae Non-biting midge 2 L DNR 1 Dixidae Dixa nebulosa A Meniscus midge 7 L DNR 2 Stratiomyidae Pachygaster atra A Soldier fly 1 L DNR 1 7

12 6. DISCUSSION WHPT analysis The current survey comprises sampling from a single day, whereas the WHPT (and BMWP) protocol requires two annual samples per sampling area, normally performed in spring and autumn. Caution should therefore be exercised in comparing these WHPT scores with those from other sites. In addition no conclusions on changes in water quality can be drawn in the absence of additional chronological samples from the same sampling points. WHPT scores are designed to monitor a very broad range of organic pollutants, including historical influences unobtainable from point sampling/chemical analysis. Other impacts such as particulate and thermal pollution can also lead to fluctuations in the populations of aquatic invertebrates, and it therefore important to consider the intervening history of the watercourse when comparing chronological data from a sampling point. The measurement of other factors by WHPT is referred to as general degradation. The WHPT protocol is designed primarily to allow comparisons between samples from the same site taken on different dates. In the current survey a significant difference is seen between the scores for sites 1 and 3 (fast-flowing shallow water with negligible submerged or emergent vegetation and steep banks) and site 2 (slow-flowing deep water with abundant submerged and emergent vegetation and a graded bank on one margin). These differences are seen in both the total WHPT scores and the number of taxa (Families) recorded (Table 2). Clearly these differences do not reflect major differences in water quality (e.g. the scores improve between sites 2 and 1) and are provisionally ascribed to differences in habitats, particularly the four elements listed above. A few of the recorded taxa receive relatively high scores under WHPT indicating that they are moderately intolerant of organic pollutants; these include Glossosomatidae (caddis flies) and Dixidae (meniscus midges). The low numbers of both Asellus aquaticus (Crustacea, Asellidae) and larval Chironomidae (Diptera) recorded also tends to support the view that the water quality is moderately good. Species Data Whilst it is often possible to ascribe immature (or early instar larvae) to a Family, identification to species usually requires examination of late instar larvae or mature specimens in good condition. For example adult males are required to reliably identify specimens of Gammarus (Gammaridae). 8

13 Species Accounts Tricladida (Flatworms) Dugesia lugubris (Dugesiidae): A widespread species characteristic of slower flowing or still water where it secretes itself in silt or beneath rocks; feeding on a range of invertebrates such a Gammarus, Oligochaetes and Chironomid larvae. Polycelis tenuis (Planariidae): A widespread species characteristic of slower flowing or still water where it secretes itself in silt or beneath rocks; feeding on a range of invertebrates such as Oligochaetes and mayfly larvae. Nematoda (roundworms): About 70 freshwater species known from the UK. May be free living or internal parasites of various invertebrates. Hirudinea (Leeches). Erpobdella octoculata (Erpobdellidae): A common leech occurring in all kinds of fresh water and feeding on a range of invertebrates. Glossiphonia complanata (Glossiphoniidae): A common leech occurring in all kinds of fresh water where it forages nocturnally, chiefly on molluscs. Helobdella stagnalis (Glossiphoniidae): A common leech occurring in all kinds of fresh water where it forages nocturnally on a range of invertebrates. Theromyzon tessulatum (Glossiphoniidae): A widespread species favouring slow-flowing and still water; it feeds on the blood of waterfowl. Oligochaeta (segmented worms): A variety of freshwater species in several Families occur in the UK, some are similar to earthworms in appearance. Mollusca (Freshwater snails) Bithynia tentaculata (Bithyniidae): Common Bithynia. A very common species found in many freshwater habitats. Lymnaea stagnalis (Lymnaeidae): Great pond snail. Our largest Lymnaeid; common in in many freshwater habitats. Often introduced (from pet shops/garden centres). Radix balthica (Lymnaeidae): Wandering snail. Common in many freshwater habitats, and a rapid coloniser of created habitats. Physa fontinalis (Physidae). Common bladder snail. Common on aquatic vegetation in many freshwater habitats. Ancylus fluviatilis (Planorbidae). River Limpet. A common mollusc occurring in all kinds of fresh water, although avoiding faster-flowing waters. Treated separately from other Planorbidae in WHPT scoring. Planorbis planorbis/carinatus (Planorbidae). Margined/Keeled Ramshorn. It was not found possible to reliably distinguish these very similar species on the basis of the specimens obtained from sampling sites 2 and 3. The species may be found together and intermediate forms occur. Both are common species of rivers, ditches and ponds. Pisidium spp. (Sphaeriidae). Pea mussels. A genus comprising 16 UK species of tiny (typically 1-3mm) freshwater mussels. Identification requires sub-specialist input and large samples. Sphaerium corneum (Sphaeriidae). Horny orb mussel. A widespread species in a range of freshwater habitats, although intolerant of pollution. Potamopyrgus antipodarum (Tateidae). Jenkins' spire snail. A widespread species found in a range of freshwater habitats, apart from still water. An introduced species first recorded in the mid-19 th century from brackish habitat in Kent; by the 1930 s however it had become widespread in inland water courses. 9

14 Species Accounts (continued) Acari - Hydrachnidae (Freshwater Mites). Many UK species; the larvae are parasitic on various invertebrates. Crustacea (crayfish, slaters and shrimps) Asellus aquaticus (Asellidae). Water Hoglouse/Slater. The very common woodlouse-like species. Pollution tolerant but present in low numbers in the DNR samples (their presence in high numbers may indicate pollutants and results in a reduction of the WHPT score) Gammarus pulex (Gammaridae). Identification is based on mature male specimens which were represented by only a small proportion of the overall samples. All the counted individuals were however inspected for characters indicative of related and similar species. In the light of this screening, no Dikerogammarus spp. were recorded. In addition no Crangonyx pseudogracilis (a Gammarus-like non-native but very widespread freshwater shrimp) were detected. Although it is considered very likely that C. pseudogracilis occurs in the DNR, it was not recorded on this occasion. Pacifastacus leniusculus (Astacidae): Signal Crayfish. One adult male was netted at site 3 and retained as a preserved specimen. Designated under Schedule 9 of the Wildlife & Countryside Act (1981). A UK WFD TAG alien species (Water Framework Directive Technical Advisory Group). London Invasive Species Initiative (LISI) Listed: Non-native crayfish: category 4: Species which are widespread for which eradication is not feasible but where avoiding spread to other sites may be required. Neuroptera (lacewings and allies) Sisyra sp. (Sisyridae). Spongeflies. Neither of the two specimens of 2 nd instar larvae from sampling site 3 was in sufficiently good condition to ascribe to species. The aquatic larvae feed on freshwater sponges whilst the small (c.1cm wingspan) adult lacewings are active at dusk (crepuscular), feeding on both honeydew and invertebrate prey such as aphids. Ephemeroptera (mayflies) Baetis rhodani (Baetidae). Large Dark Olive. One of the UK s commonest mayflies. The larvae favour riffle habitats and there are two generations per year. Caenis horaria (Caenidae). Anglers curse. A widespread but often rather local mayfly. The larvae inhabit mud and silt, and the small (c.7mm body length) adults may be active between May and September. Odonata - Zygoptera (damselflies). Calopteryx splendens (Calopterygidae). Banded demoiselle. The larvae were found primarily among submerged vegetation in the slower moving water at sample point 2. 8 of the 16 specimens from that location were sufficiently mature to ascribe reliably to species. The larvae require slow-flowing rivers with submerged vegetation, and although generally common in England and Wales this species is rather local in Greater London, depending on the availability of suitable habitat. 10

15 Species Accounts (continued) Trichoptera (caddisflies) Agapetus fuscipes (Glossosomatidae). Common throughout the country; larvae in stony river beds. Hydropsyche angustipennis (Hydropsychidae). A common species, primarily in lowland rivers and streams. Hydropsyche pellucidula (Hydropsychidae). A common species of streams and rivers. Athripsodes cinereus (Leptoceridae). A common species of streams, rivers and lakes. Mystacides azurea (Leptoceridae). A common species of streams, rivers, ponds and lakes. Molanna angustata (Molannidae). A common species of ponds, lakes, canals and slow rivers. The specimen from fast-flowing water (DNR sampling point 3 - upstream) is an apparent anomaly which might represent downstream drift from a slow-flowing stretch upstream? Coleoptera (beetles) Elmis aenea (Elmidae). A Riffle beetle. A common species of running water where it clings to submerged stones and riverside vegetation. Oulimnius tuberculatus (Elmidae). A Riffle beetle. A local species of running water where it appears to show a preference for submerged exposed root systems. Diptera (flies) Chironomidae. Non-biting midges. A large family of flies with well over 600 species recorded from the British Isles. Pollution tolerant but present in low numbers in the DNR samples (their presence in high numbers may indicate pollutants and results in a reduction of the WHPT score). Dixa nebulosa (Dixidae). A Meniscus midge. The most frequently encountered member of the Genus in lowland England, although records for SE England are rather sparse (NBN Gateway - see References). The surface-dwelling (meniscus) larvae are found among stands of emergent vegetation. Pachygaster atra (Stratiomyidae). A Soldier fly. The larva of this common species is not generally considered to be aquatic, and the species does not of course belong in this analysis if the solitary larva netted at sampling point 1 had simply fallen into the water. However there are records of larvae from wet decaying vegetation (Stubbs, 2001) so it might be associated in this instance with marginal semi-aquatic habitat. 11

16 Species Designations No species with conservation designations were recorded in the course of the survey. These designations include: Protected by Statute, Red Data Book, Nationally Scarce, S41 (species of principal importance for the conservation of biodiversity in England), Greater London BAP species or species prioritised in the Biodiversity Action Plans for Hounslow or Richmond upon Thames. The Signal Crayfish Pacifastacus leniusculus (Astacidae) is an invasive species as designated under Schedule 9 of the WCA (1981); by the Water Framework Directive Technical Advisory Group (WFD TAG) and in the London Invasive Species Initiative (LISI) List. Conservation-worthy Species: 1. Although both may be common and widespread elsewhere in the country, in the surveyor s opinion (and in the absence of specific published evidence) the following two species should be considered as Local or Very Local in Greater London, and therefore legitimate targets for habitatbased conservation measures. 12 Oulimnius tuberculatus (Elmidae). A Riffle beetle. Key habitat requirements include riffles and particularly submerged root tangles. Calopteryx splendens (Calopterygidae). Banded Demoiselle. Key habitat requirements include slower moving deeper water with abundant submerged vegetation. Acquainting volunteers and contractors with these species and their habitats would tend to decrease the risk that key habitats are disrupted in the course of other works. Conservation-worthy Species: 2. The following species which were recorded at sampling point 2 each have a specific requirement for slow-moving water. Dugesia lugubris Polycelis tenuis Theromyzon tessulatum Ancylus fluviatilis Calopteryx splendens Molanna angustata Flatworm Flatworm Leech River Limpet Banded Demoiselle Caddis fly Bearing in mind that these records are the result of sampling for monitoring rather than (more thorough) ecological survey, they provide preliminary evidence for the presence of a community of invertebrates in the DNR associated with slow-flowing water, and thus emphasise the value of these areas alongside the faster flowing stretches. 7. RECOMMENDATIONS In carrying out improvement works to the DNR, avoid as far as practicable disrupting the habitats associated with the conservation-worthy species detailed above. No WHPT data for comparative purposes is available at this time from urban rivers in SE England via the Environment Agency Data Explorer (see References and Bibliography). It would clearly be of some interest to be able to benchmark the DNR WHPT and derived scores against those obtained from similar urban rivers in the region. In that case it would be worthwhile to obtain such figures from other sources, if practicable. In planning further survey of aquatic invertebrates, in addition to repeat WHPT survey, consider ecological survey sampling if it is thought desirable to gain a clearer understanding of the invertebrate species complement of the DNR.

17 8. REFERENCES & BIBLIOGRAPHY [To activate links add a colon after http or https; e.g. http// to Nomenclature of taxa follows the Natural History Museum UK Species Inventory, which provides authorities: http// Bryce, D. & Hobart, A. (1972). The Biology and Identification of the Larvae of the Chironomidae (Diptera). Entomologist's Gazette 23; Buglife/Environment Agency (2015). Crayfish Identification, Distribution and Legislation. https//ww.buglife.org.uk/sites/default/files/final%20crayfish%20id%20distribution%20 and%20legislation%2023%2006%2015_jg.pdf Chadd, R. (2010). Assessment of Aquatic Invertebrates. In: Hurford, C., Schneider, M. & Cowx, I. (eds.). Conservation Monitoring in Freshwater Habitats: A Practical Guide and Case Studies. Springer. Cham, S. (2009). Field Guide to the larvae and exuviae of British Dragonflies; Volume 2: Damselflies. The British Dragonfly Society, Peterborough Constable, D. (2014). Notes on the importance of sexing Gammaridae for identification: using Dikerogammarus as an example. V1. Environment Agency. https// Davy-Bowker, J. (2015). RIVPACS/RICT Bioassessment Training Manual. Freshwater Biological Association, Wareham. Unpublished. Denton, J. (2007). Water Bugs and Water Beetles of Surrey. Surrey Wildlife Trust, Pirbright. Disney, R. H. L. (1999). British Dixidae (Meniscus Midges) and Thaumaleidae (Trickle Midges): Keys with Ecological Notes. Freshwater Biological Association Scientific Publication No. 56. Dobson, M. (2013). Family-level keys to freshwater fly (Diptera) larvae. Freshwater Reviews 6 (1). The Freshwater Biological Association. Dobson, M. (2013). Identifying Invasive Freshwater Shrimps and Isopods. Freshwater Biological Association. Revised Edition, May https// Dobson, M., Pawley, S., Fletcher, M. & Powell, A. (2012). Guide to Freshwater Invertebrates. Freshwater Biological Association Scientific Publication No. 68. Edington, J. M. & Hildrew, A. G. (1995). A Revised Key to the Caseless Caddis Larvae of the British Isles: with Notes on their Ecology. Freshwater Biological Association Scientific Publication No. 53. Elliot, J M. (2009). Freshwater Megaloptera and Neuroptera of Britain and Ireland: Keys to the Adults and Larvae, and a Review of their Ecology. Freshwater Biological Association Scientific Publication No. 65. (2012 reprint including minor corrections). Elliot, J. M. and Dobson, M. (2015). Freshwater Leeches of Britain and Ireland: Keys to the Hirudinea and a Review of their Ecology. Freshwater Biological Association Scientific Publication No

18 Elliot, J. M. & Humpesch, U. H. (2010). Mayfly larvae (Ephemeroptera) of Britain and Ireland: Keys and a Review of their Ecology. Freshwater Biological Association Scientific Publication No. 66. (2012 reprint including minor corrections). Environment Agency (2012). Freshwater macro-invertebrate sampling in rivers. Operational instruction 018_08. (Unpublished procedures manual). Environment Agency Catchment Data Explorer. http//environment.data.gov.uk/catchmentplanning/ Gledhill, T., Sutcliffe, D. W. and Williams, W. D. (1993). British Freshwater Crustacea Malacostraca: a Key with Ecological Notes. Freshwater Biological Association Scientific Publication No. 52. Holdich, D. M. (2009). Identifying crayfish in British waters. In: Brickland J., Holdich D. M. and Imhoff, E. M. (eds.) (2009). Crayfish Conservation in the British Isles. Conference Proceedings; 25 th March 2009, Leeds, UK. Holland, D. G. (1972). A Key to the Larvae, Pupae and Adults of the British Species of Elminthidae. Freshwater Biological Association Scientific Publication No. 26. Hounslow Biodiversity Action Plan Partnership. Hounslow Biodiversity Action Plan http// Kerney, M. (1999). Atlas of the Land and Freshwater Molluscs of the British Isles. Harley Books, Colchester. Killeen, I., Aldridge, D., and Oliver, G. (2004). Freshwater Bivalves of Britain and Ireland. Field Studies Council, Shrewsbury: Occasional Publication 82. Killeen, I. (1992). The Land and Freshwater Molluscs of Suffolk: An Atlas and History. The Suffolk Naturalists Society, Ipswich. London Invasive Species Initiative. http// Macan, T. T. (1977). A Key to the British Fresh- and Brackish-water Gastropods, with notes on their ecology. Freshwater Biological Association Scientific Publication No. 13. NBN Gateway: https//data.nbn.org.uk/ Nilsson, A. N. (ed.) (1996). Aquatic Insects of North Europe: A Taxonomic Handbook. Volume 1: Ephemeroptera, Plecoptera, Heteroptera, Megaloptera, Neuroptera, Coleoptera, Trichoptera and Lepidoptera. Apollo Books, Stenstrup. Nilsson, A. N. (ed.) (1997). Aquatic Insects of North Europe: A Taxonomic Handbook. Volume 2. Odonata - Diptera. Apollo Books, Stenstrup. Reynoldson, T. B. and Young, J. O. (2000). A Key to the Freshwater Triclads of Britain and Ireland. Freshwater Biological Association Scientific Publication No. 58. Richmond Biodiversity Group (2006). Biodiversity Action Plan: London Borough of Richmond upon Thames. http// Stubbs, A. and Drake, M. (2001). British Soldierflies and their Allies. British Entomological and Natural History Society. Wallace, I. D., Wallace, B. & Philipson, G. N. (2003). Keys to the Case-bearing Caddis Larvae of Britain and Ireland. Freshwater Biological Association Scientific Publication No. 61. Wallace, I. D. (1991). A Review of the Trichoptera of Great Britain. Research and Survey in Nature Conservation No. 32. Nature Conservancy Council, Peterborough. 14

19 9.1. Appendix 1: Map showing locations of the Sampling Areas Grid References are given in Table 1 p2. 15

20 9.2. Appendix 2: Photographs All photographs appearing in this report Ilse Steyl Photo 1: Sampling Site 1 (downstream sample) Photo 2: Sampling Site 2. Note the deeper water and submerged vegetation. Photo 3: Sampling Site 3 (upstream sample) Photo 4. Signal Crayfish (Pacifastacus leniusculus) from Sampling Site 3. This male had lost its left fore-limb (cheliped) and a new limb is in the process of regenerating. Currently in coll. J.R.Dobson. Photo 5: Sampling at Site 3 Photo 6: Sampling at Site 2 16

21 9.3. Appendix 3: Risk Assessment Risk Assessment Make Natural Ltd. (Ecological Services) Risk Ranking: Likelihood x Severity = Risk (High, Medium, Low) Severity Likelihood Low Medium High Low Low Low Medium Medium Low Medium Medium High Medium Medium High Project: Invertebrate sampling of DN River; WHPT and preliminary species audit. Activity: Kick Sampling for WHPT RA carried out by: John Dobson (Director) Other personnel: Ilse Steyl (Green Corridor). Gareth Ryman (Hounslow Council) Project Ref: MNP0255 Date: 13 October 2015 Site: Lower Duke of Northumberland s River (DNR) in Hounslow and Richmond upon Thames Activity Hazard Who s at risk Controls in place Risk Further controls required Fieldwork Lone working na n/a: Surveyor accompanied throughout by experienced field worker(s), all with mobile phones. Fieldwork Water sampling Water sampling Minor scratches, stings, bruises Trip hazards, broken glass etc. in river Waterborne infections All Surveyor Surveyor All are experienced field workers. First-aid kit carried. Ongoing surveillance by surveyor and from bank. Water not turbid and river bed visible. Surveyor free of open cuts or scratches. Antiseptic hand ointment applied regularly. na na na L na na L na na L na na Residual Risk 17

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