River Mole Derogation Fisheries Survey Thames Metropolitan 1989 S.Col Clough
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NATIONAL RIVERS AUTHORITY THAMES REGION. RIVER MOLE DEROGATION FISHERIES SURVEY THAMES METROPOLITAN 1989 S.COL CLOUGH (AREA FISHERIES OFFICER) C.DUTTON (FISHERIES OFFICER) N.FOULKES (FISHERIES OFFICER) J.LYONS (FISHERIES ASSISTANT) COMPILED BY: N.FOULKES Ref: CM089 ENVIRONMENT AGENCY CONTENTS Page No. CONTENTS ACKNOWLEDGEMENTS 5 1. SUMMARY 6 2. INTRODUCTION 9 2.1 Description of the Watercourse 9 2.2 Geology and Hydrogeology 14 2.3 Main discharges 19 2.4 Pollution Incidents 22 2.5 Fish mortalities 23 2.6 Fisheries Management History 24 3. AIMS AND OBJECTIVES 33 3.1 Overall aims of Surveys 33 3.2 River Classification 33 3.3 Specific Aims 34 4. METHODS 35 4.1 Site Selection 35 4.2 Capture and Data Aquisition 35 4.3 Data Analysis 36 4.4 Health Examination 36 4.5 Macroinvertebrates 36 4.6 Water Quality 36 Page No. 5. RESULTS 39 5.1 Site Results 39 5.2 Survey Results 87 5.3 Fish Health 89 5.4 Water Quality 89 5.5 Macroinvertebrates 90 6. DISCUSSION 99 7. CONCLUSIONS 107 8. RECOMMENDATIONS 109 9. REFERENCES 112 10. APPENDICES 113 (i) Classification of river quality 113 (ii) River quality objectives 1.14 (iii) EEC Directive list of determinands 115 (iv) Site codes and locations 116 (v) R.Mole restocking 1987-1990 117 (vi) R.Mole fish mortalities 1986-1990 119 (vii) NRA site coding system 120 (viii) R.Mole river quality assessment 121 (October 1989 - September 1990. 11. ORDER FORM LIST OF FIGURES Figure Page No* 1. River Mole, Major Urban Areas 10 2. River Mole, Diagrammatic Representation. 11 3. River Mole, Geology. 15 4. River Mole, Horley Gauging Station. 16 5. River Mole, Kinnersley Manor Gauging Station. 17 6. River Mole, Esher Gauging Station. 18 7. River Mole, Survey Map. 32 8. Site Report, Upper Gatwick Stream 1990 (GSFA). 40 9. Biomass and Density, Upper Gatwick Stream 1990 (GSFA) . 42 10. Biomass and Density, Upper Gatwick Stream 1986 (GSFI). 43 11. Length/Frequency for Brown Trout, Gudgeon and Roach, 44 Upper Gatwick Stream 1986 (GSFI). 12. Site Report, Gatwick Stream d/s Crawley STW, 1990 (GSPA) 46 13. Biomass and Density, Gatwick Stream d/s Crawley STW, 47 1990 (GSPA). 14. Length/Frequency for Chub, Dace, Gudgeon & Pumpkinseed, 48 Gatwick Stream d/s Crawley STW, 1990 (GSPA). 15. Length/Frequency for Roach, Gatwick Stream d/s Crawley 49 STW, 1990 (GSPA). 16. Biomass and Density, Gatwick Stream d/s Crawley STW, 50 1986 (GSPI). 17. Length/Frequency for Dace and Gudgeon, Gatwick Stream 51 d/s Crawley STW, 1986 (GSPI). 18. Site Report, River Mole, u/s Horley STW, 1990 (MOPA). 53 19. Biomass and Density, River Mole, u/s Horley STW, 1990 (M3PA). 55 20. Length/Frequency for Bream, Dace, Gudgeon and Roach, 56 River Mole, u/s Horley STW, 1990 (MOPA). 21. Biomass and Density, River Mole u/s Horley STW 57 1986 (MOPI). 22. Length/Frequency for Dace, Perch and Roach, 58 Rver Mole, u/s Horley STW, 1986 (MOPI). 1 . Site Report, River Mole, u/s Sidlow Bridge 1990 (MONB). Biomass and Density, River Mole, u/s Sidlow Bridge 1990 (MONB). Length/Frequency for Dace, Gudgeon and Roach River Mole, u/s Sidlow Bridge, 1990 (MONB). Biomass and Density, River Mole, u/s Sidlow Bridge 1986 (M0N2). Length/Frequency for Bream, Dace and Roach, Rver Mole, u/s Sidlow Bridge, 1986 (MDN2). Site Report, River Ember u/s Esher STW, 1990 (MOJA). Biomass and Density, River Ember u/s Esher STW 1990 (MOJA). Length/Frequency for Perch, River Buber u/s Esher STW, 1990 (MOJA). Site Report, Old Mole Channel, 1990 (MOJB). Biomass and Density, Old Mole Channel, 1990 (MOJB). Length/Frequency for Chub, Dace, Eel and Perch, Old Mole Channel, 1990 (MOJB). Length/Frequency for Pike and Roach, Old Mole Channel, 1990 (MOJB). Biomass and Density, Old Mole Channel, 1986 (M0J2). Length/Frequency for Chub, Dace, Eel and Gudgeon, Old Mole Channel 1986 (M0J2). Length/Frequency for Roach, Old Mole Channel, 1986 (M0J2). Site Report, River Ember d/s Esher STW 1990 (MOJC). Biomass and Density, River Einber d/s Esher STW 1990 (MOJC). Length/Frequency for Dace and Roach, River Ember d/s Esher STW 1990 (MOJC). Biomass and Density, River Einber d/s Esher STW 1986 (M0J3). Length/Frequency for Dace, Eel, Gudgeon and Ruffe, River Einber d/s Esher STW 1986 (M0J3) . Page No. 43. Length/Frequency for Roach, River Einber d/s Esher STW 1986 <M0J3). 84 44. Biomass comparison for all sites (1986 and 1990). 86 3. LIST OF TABLES Table No. Page No. 1. Water Quality Compliance 89 2. Macroinvertebrate Results. 90 4. ACKNCWLE3DGEMEWTS I am extremely grateful to the following people, for the assistance they provided to me, in the preparation of this survey report. Members of the Waltham Cross Fisheries East Team, for assistance with the fieldwork. David Van Beesten {Flood Defence Engineer, Lower Thames). Mike Hoare (Senior Groundwater Protection Officer, Crossness). Liz Vincent (Scientist, Catchment Control, Reading). Paul Greaves (District Pollution Officer, Guildford). Richard Ashby Crane (Biologist, Fobney). Paul Logan (Senior Biologist, Fobney). Alan Butterworth (Senior Fisheries Officer West. Guildford). John Sutton (Area Fisheries Officer, Guildford). Roy Ballinger (River Mole Preservation Ass. & Leatherhead D.A.S.). John Davies (Horley Piscatorial Society). and to anyone whom I have forgotton that helped in any way. 1. SUMMARY Seven sites were fished above and below three major STW discharges at Crawley, Horley and Esher, between October 1989 and May 1990. These sites were compared with six almost identical sites completed during the 1986 survey (Ref. CM086). Good quality mixed coarse fisheries were found below Crawley, with fair to good recruitment observed in the dace, roach and gudgeon. The dominant species were roach, dace, chub, gudgeon and eel. Brown trout, brook lamprey, common bream, perch, pike, pumpkinseed, rudd, tench, common carp, bleak and ruffe were also present. The minor species, minnow, bullhead, Stoneloach and three spined stickleback were also observed. During the 1990 survey, fish biomasses were higher than at all comparable 1986 sites. Species diversity has improved with up to fourteen species present at one site. Only one of the three EC designated, cyprinid fisheries achieved the internally set target of 20 gms/m 2 (M3JB/Old Mole Channel). Both MOJA and MOJC (u/s and d/s of STW) , which are 25-26 metre wide, 2.0 metre deep trapezoidal channels, with little or no instream macrophytes, failed, MOJA by a wide margin. Channel topography and lack of instream macrophytes are perceived as the reason for the failures. At the three non EC designated sites, on the Lower Gatwick Stream and Upper Mole, biomasses ranged from 16.44 gms to 40.59 gms. Of more consequence, was the fact that recruitment could be observed in some of the major riverine species. During the 1986 survey these sites were noted as lacking in recruitment. Chemical water quality has not deteriorated, and appears to be more consistent than in the past. Water quality compliance is high. The macroinvertebrate data splits the seven sites of the survey into two distinct sections. The four sites on the Gatwick Stream/Upper Mole fall well below their predicted biotic scores and are influenced by discharges and the increasing urbanisation of the area. The three sites on the Mole/&nber Flood Alleviation Scheme (FAS) which largely agree with their predicted biotic scores. Further improvements can be expected at the upper four sites as both Horley and Crawley STW's have recently undergone major refurbishment and the discharge from Gatwick Airport will evetly be treated at Crawley Since July 1989, there have been no significant fish mortalities on the Mole or its tributaries. The fish corrmunities found at comparable sites, during surveys reported during 1967, 1982 and 1986 are broadly similar to those of 1990. However when the major riverine species are considered subtle changes are occurring. Because of recent lack of flow and the consequent lack of dilution of treated sewage effluent, roach are dominating at six of the seven 1990 sites. Dace are regarded as effluent tolerant and are usually associated with the faster flowing sections of the river. They are becoming dominant on the Lower Gatwick Stream and Upper Mole sections of the river. The chub population is in decline. Recruitment is poor and the only remaining substantial population is to be found on the Old Mole Channel and this is composed of older fish. Brown Trout are dominant at the Upper Gatwick Stream Site (GSFA) . This is an important relict, local population, which is self maintaining. A new species, brook lamprey appears to be colonising the Gatwick Stream. The alien species pumpkinseed are establishing themselves in the Gatwick Stream and in the Upper Mole. Eels now penetrate the main river as far as Horley Weir. Their numbers and size ranges appear to be increasing. Stocking on the Lower Gatwick Stream/Upper Mole seems to have been on unqualified success. A number of environmental factors are perceived as having a significant effect upon fisheries. i) the whole catchment is suffering from low flows and reduced dilution of treated sewage effluent. ii) the Upper Gatwick Stream has problems with accelerating urbanisation. iii) the Lower Gatwick Stream/Upper Mole has problems with STW effluents, winter run-off from Gatwick Airport, urban run-off and downstream impoundments. iv) In the Mole/Elnber FAS channel topography and lack of instream macrophytes are major constraints. 8. 2. IOTRODUCTION 2.1. Description of the Watercourse The River Mole is one of the major tributaries of the Thames. The Mole 2 catchment covers 487 km (5%) of the Thames catchment and contributes 6% of the freshwater discharge at Teddington.