The New Forest LIFE 3 Fisheries response to restoration Report August Draft Version 1.0 August 2006

Transcription

1 The New Forest LIFE 3 Fisheries response to restoration Report August 2006 Draft Version 1.0 August 2006 by D-J Gent C.Env Ecological Appraisal Team Hampshire and Isle of Wight Author: D- J Gent 1

2 Author: D- J Gent 2

3 How have the fish populations of the New Forest responded to the LIFE 3 restoration works? Project reference LIFE 02/NAT/UK/8544 August 2006 Final version 1.2 D-J Gent CEnv Ecological Appraisal Team Environment Agency Colvedene Court Wessex Way Colden Common Winchester, Hampshire SO21 1WP Author: D- J Gent 3

4 Table of contents Table of contents Executive summary Purpose Introduction Method Electric fishing Site selection Locations of the survey sites Habitat Survey dates Conditions Results Survey site information...14 Site 1 DS Blackwater Bridge (control)...14 Site 2 Anderwood (control)...15 Site 3 Hart Hill (control)...16 Site 4 Dog Kennel Bridge (impacted)...17 Site 5 Poundhill Heath (control)...18 Site 6 Lucas Castle (control)...19 Site 7 Highland Water Reptillary (control)...20 Site 8 Withybed Bottom (impacted)...21 Site 9 DS Warwickslade Bridge (control)...22 Site 10 Burley Lodge enclosure (control)...23 Site 11 Dames Slough Enclosure (impacted)...24 Author: D- J Gent 4

5 Site 12 Blackensford lawn (impacted)...25 Site 13 Woolsfield Hill (control)...26 Site 14 Fletchers Water (control)...27 Site 15 Rhinefield (impacted) Number of species Density Species composition Biomass Growth rates Scale analysis for age and growth Habitat evaluation and interpretation Discussion Conclusions Further work...71 References...71 Appendix HABSCORE evaluation at each site...72 Author: D- J Gent 5

6 1.0 Executive summary Fifteen sites were identified, fished and the habitat scored (using HABSCORE) for suitability for salmonids in 2003 and The sites were divided between sites to be restored and control sites. A before, after, control, impact (BACI) study was used to assess how the fish populations have responded to the New Forest LIFE restoration work. The most frequent species found were brown trout / sea trout, bullhead, eel, lamprey, minnow and stone loach. Pike, chub and bleak were also recorded. As expected fish biomass and density at impacted sites have not recovered to pre-restoration levels at the restored LIFE 3 sites. Fish of all species were removed and relocated to prevent fish kills prior to the work. No significant difference in number of species caught was identified between 2003 and 2006 and between control and impacted sites. Brown trout / sea trout and bullhead density reduced substantially in impacted stretches after the restoration work. Species composition altered in both control and impacted sites between 2003 and At least five age classes of brown trout / sea trout were present in 2006 at both control and impacted sites. On average, total biomass (all species) reduced at both control and impacted sites between 2003 and There was not difference identified in length weight relationships for brown trout / sea trout between control and impacted sites in A reduced growth rate in brown trout / sea trout was identified at Dog Kennel Bridge between 2003 and 2004 (prior to any restoration work at the site). Habitat changes were predicted to benefit densities of some age classes of brown trout / sea trout on a site-specific basis. However, these changes were not statistically significant using the HABSCORE model. The observed density of salmonids was lower than would be predicted for the habitat available at all sites in 2006 Author: D- J Gent 6

7 Positive signs of recovery were identified but fish populations have not yet recovered to pre-restoration densities at impacted sites. The restoration increased the length of the sites by over 1600 metres. This has increased the amount of habitat available for a range of fish species. Author: D- J Gent 7

8 1.1 Purpose The purpose of this paper is to report the fifteen electric fishing surveys carried out in June and July 2003 and then repeated in May The aim was to monitor how the fish stocks have responded to the restoration works of the New Forest LIFE project. 1.2 Introduction The objective of the project Sustainable Wetland Restoration in the New Forest was to restore 604 ha of rare priority habitat in the New Forest Special Area of Conservation (csac). Fish and macro-invertebrate monitoring was required to evaluate the biological response to the restoration. Fish monitoring was to include Annex 2 species such as bullhead and brook lamprey. This direct measure was required to show how fish species responded to the restoration works within the timeframe of the LIFE 3 project. It was anticipated before the work started that the full biological changes to the New Forest would not be seen until a number of years after the restoration. However, the timescale for the project required an assessment by 2006, in some case only months after the work was completed. The biology of impacted sites were at different stages of responding to the restoration work and therefore do not give the final verdict of the success of the project from a fisheries perspective. The sites to be restored had meanders re-established on channelised stretches. This restoration therefore increased the length of river increasing available habitat for fish. Detecting changes in fisheries populations that have high natural temporal and spatial variability, to assess the presence or scale of an effect using a few discreet surveys is challenging. Invertebrate or macrophyte surveys can increase the precision in detecting changes and estimating the level of recovery. Fish are affected by periodic events such as changes in water quality, light, nutrients, temperature, salinity and biological processes such as spawning or feeding that can all cause somatic growth checks. This report outlines the results of the 2003 and 2006 surveys. These will serve as a baseline to provide a reference for future years and will be useful when Author: D- J Gent 8

9 compared to future surveys. The results need be placed into context of the prevailing conditions of severe drought in 2005 and It should be noted that brown trout and sea trout are the same species (Salmo trutta fario L.). Where only trout or brown trout is used it refers to the species that includes sea trout. Author: D- J Gent 9

10 2.0 Method The sampling method used was pulsed DC electric fishing with one or two anodes. Sites were fished three times for depletion (using upstream and downstream stop nets) allowing the calculation of a population estimate. Scales were removed from the fish for growth rate and ageing purposes. These were compared against other brown trout populations and the national growth (length / weight) curves. The method adhered to the Fisheries Monitoring Fisheries Monitoring Programme Work Instruction 2.1:Electric Fishing in Rivers. Each site was then assessed for salmonid habitat suitability using the HABSCORE modelling methodlogy. This evaluates the habitat features available for salmonids of all sizes. 2.1 Electric fishing Site selection A BACI (Before, After, Control Impact) study was carried out using 15 sites surveyed in 2003 and repeated in Seven sites were identified as control sites where no restoration was planned and eight sites were on reaches that were to be restored (impacted) in the project. The control sites were as follows: Site Upstream grid reference 1 DS Blackwater Bridge SU Anderwood SU Hart Hill SU Dog Kennel Bridge SU Poundhill Heath SU Lucas Castle SU Highland Water Reptillary SU The to be restored sites were as follows: Site Upstream grid reference 8 Confluence Withybed Bottom SU DS Warwickslade Bridge SU Burley Lodge enclosure SU Dames Slough enclosure SU Blackensford Lawn SU Woolsfield Hill SU Fletchers Water SU Rhinefield SU Author: D- J Gent 10

11 The sites were between 75 and 100 metres in length and were fished three times. Each run caught a larger proportion of the resident population catching fewer on each subsequent run enabling population estimates to be calculated through standard depletion (using the Carle and Strub method 1978). Each site was sectioned off with upstream and downstream stop nets to avoid immigration or emigration of fish during the survey. Fish were measured and weighed and scales taken for age and growth analysis. Lamprey and bullhead could not be weighed effectively as they had so little mass. They were measured and lengths recorded. The growth of brown trout was compared against national brown trout growth rates. As a result of changes to the planned works during the groundworks phase of the project the actual sites that were restored were as follows: Site Upstream grid reference 4 Dog Kennel Bridge SU Confluence Withybed Bottom SU Dames Slough enclosure SU Blackensford Lawn SU Rhinefield SU The sites that were not restored and therefore control sites were: Site Upstream grid reference 1 DS Blackwater Bridge* SU Anderwood SU Hart Hill SU Poundhill Heath SU Lucas Castle SU Highland Water Reptillary SU DS Warwickslade Bridge SU Burley Lodge enclosure SU Woolsfield Hill SU Fletchers Water SU *Debris work was done at the DS Blackensford Bridge site but no channel engineering was carried out. Therefore for the purposes of the fisheries report the site was treated as a control. Author: D- J Gent 11

12 2.1.2 Locations of the survey sites Habitat Habitat is a fundamental factor when studying fish populations and studying habitat allows the fish population captured to be compared to what would be expected given the prevailing conditions. The habitat available to salmonids was assessed using the HABSCORE methodology. This consistent and Author: D- J Gent 12

13 repeatable method identified key habitat features. The fish survey results were then compared to a predicted population score based on carrying capacity of the site (see appendix 1). HABSCORE is the accepted standard Environment Agency package for predicting salmonid densities based on habitat variables. It measures and evaluates stream salmonid habitat features based on a series of empirical statistical models relating the population size of five salmonid species/age combinations to observed habitat variables. It requires information from three sources, relating to: site specific habitat features; catchment features; and observed salmonid populations at a site. Specific habitat features include the assessment of substrate, flow and sources of cover for over 10cm trout. This is described in more detail in the report by WRc-NSF Ltd (1999) HABSCORE for Windows A guide to field survey methods. The work was originally undertaken by WRc plc under NRA R&D contract 338. HABSCORE enables a prediction to be made (with confidence intervals) of how the restoration has altered the availability of habitat for three size ranges of brown trout / sea trout. 2.3 Survey dates The surveys were carried out on the 16, 18, 19, 24, 25, 26, 27, 30 June and 1,2 July 2003 and 4, 5, 9, 16, 17, 18 and 31 May 2006 by the Ecological Appraisal and Fisheries Recreation and Biodiversity teams of the Environment Agency. 2.4 Conditions River flow and volume were substantially reduced in 2006 as a result of a second very dry winter in 2005/06. Across the south of England groundwater levels had not had sufficient water to recharge and reduced rainfall have resulted in a number of water quality and flow impacts for fish survival, growth and distribution. High water temperatures (in excess of 19 o C) were also a concern for salmonid fish. Author: D- J Gent 13

14 3.0 Results 3.1 Survey site information Site 1 DS Blackwater Bridge (control) Site Details Survey Date 25/6/3 and 16/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackwater Site Name DS Blackwater Bridge U/S NGR SU Map Author: D- J Gent 14

15 Site 2 Anderwood (control) Site Details Survey Date 19/6/3 and 18/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Bratley Water Site Name Anderwood U/S NGR SU Map Author: D- J Gent 15

16 Site 3 Hart Hill (control) Site Details Survey Date 27/6/3 and 17/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackensford Brook Site Name Hart Hill U/S NGR SU Map Author: D- J Gent 16

17 Site 4 Dog Kennel Bridge (impacted) Site Details Survey Date 21/7/3 and 18/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackwater Site Name Dog Kennel Bridge U/S NGR SU Map Author: D- J Gent 17

18 Site 5 Poundhill Heath (control) Site Details Survey Date 27/6/3 and 5/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Highland water Site Name Poundhill Heath U/S NGR SU Map Author: D- J Gent 18

19 Site 6 Lucas Castle (control) Site Details Survey Date 16/6/3 and 4/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Highland Water Site Name Lucas Castle U/S NGR SU Map Author: D- J Gent 19

20 Site 7 Highland Water Reptillary (control) Site Details Survey Date 18/6/3 and 5/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Highland Water Site Name Reptillary U/S NGR SU Map Author: D- J Gent 20

21 Site 8 Withybed Bottom (impacted) Site Details Survey Date 18/6/3 and 4/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Highland Water Site Name Withybed Bottom U/S NGR SU Map Author: D- J Gent 21

22 Site 9 DS Warwickslade Bridge (control) Site Details Survey Date 24/6/3 and 17/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Warwickslade Cutting Site Name DS Warwickslade Bridge U/S NGR SU Map Author: D- J Gent 22

23 Site 10 Burley Lodge enclosure (control) Site Details Survey Date 1/7/3 and 31/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackensford Brook Site Name Burley Lodge Enclosure U/S NGR SU Map Author: D- J Gent 23

24 Site 11 Dames Slough Enclosure (impacted) Site Details Survey Date 24/6/3 and 17/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackwater Site Name Dames Slough Enclosure U/S NGR SU Map Author: D- J Gent 24

25 Site 12 Blackensford lawn (impacted) Site Details Survey Date 20/6/3 and 18/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackensford Brook Site Name Blackensford Lawn U/S NGR SU Map Author: D- J Gent 25

26 Site 13 Woolsfield Hill (control) Site Details Survey Date 30/6/3 and 17/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Brately Water Site Name Woolsfield Hill U/S NGR SU Map Author: D- J Gent 26

27 Site 14 Fletchers Water (control) Site Details Survey Date 26/6/3 and 9/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackwater Site Name Fletchers Water U/S NGR SU Map Author: D- J Gent 27

28 Site 15 Rhinefield (impacted) Site Details Survey Date 26/6/3 and 9/5/6 Survey Type Quantitative Catchment Lymington Subcatchment Blackwater Site Name Rhinefield U/S NGR SU Map Author: D- J Gent 28

29 3.2 Number of species 15 sites were surveyed using quantitative techniques in 2003 and The sites were split between those that were to be restored and those that would not be restored (a control). The number of fish species counted at each site was calculated and an average was taken. Before After Not restored (Control) 5.3 ( ) 5.4 ( ) Restored (Impacted) 5 ( ) 5 ( ) (Spread of 95% confidence intervals (CI) in brackets) As expected the control sites that were not restored had on average, the same number of species present before and after the LIFE 3 work. Sites that were restored had on average fewer species both before and after the work although this is not statistically significant (see CI's). Therefore there is no significant difference in number of species caught between control and impact sites both before and after the restoration work. Therefore there is no evidence to suggest that the restoration work has had a negative affect on number of species caught. Author: D- J Gent 29

30 3.3 Density Fish density is important factor for understanding food availability and habitat utilisation, and therefore potential growth rates. The following are stock diagrams for brown trout / sea trout density (fish per 100m 2 ) for restored sites before and after the restoration work. They show that the brown trout / sea trout density is significantly reduced after the restoration work at the impacted sites. As many as fish as possible, of all fish species, were removed and relocated from works sites prior to restoration disturbance to prevent fish kills. Therefore fewer fish would be expected at impacted sites. Brown trout / sea trout populations had not re-established themselves to pre-restoration levels at impacted sites. River length was also increased and therefore more habitat was available. This could reduce fish densities at the survey site. Author: D- J Gent 30

31 Brown trout density (showing 95% confidence intervals) in Brown trout per 100 m Dog Kennel Bridge Withybed Bottom Dames Slough Blackensford Rhinefield Site Brown trout density (showing 95% confidence intervals) in Brown trout per 100m Dog Kennel Bridge Withybed Bottom Dames Slough Blackensford Lawn Rhinefield Site Author: D- J Gent 31

32 The following histograms show the density of bullhead at all sites before and after the restoration works. Populations are much lower in 2006 than in 2003 at impacted sites. Bullheads were also removed from sites prior to works. However, bullhead numbers have also declined at the control sites, not impacted by the restoration work. This may be natural variation within the bullhead population rather than a result of the restoration works and therefore may warrant further investigation. It should also be noted that quantitative bullhead population estimates using electric fishing have wide confidence intervals. Density of Bullhead per 100m Bullhead per 100m Anderwood Blackensford Burley Lodge Dames Slough Dog Kennel Bridge DS Blackwater Bridge Fletchers Hart Hill Poundhill Heath Lucas Castle Reptillary Rhinefield Warwickslade Withybed Bottom Woolsfield Site Density of Bullhead per 100m (restored sites in pink) Bullhead per 100m Anderwood Blackensford Burley Lodge Dames Slough Dog Kennel Bridge DS Blackwater Bridge Fletchers Hart Hill Lucas Castle Poundhill Heath Reptillary Rhinefield Warwickslade Withybed Bottom Woolsfield Site Author: D- J Gent 32

33 The following histograms show the average total species density at the control and impacted sites before and after the restoration. Average species density at control and impacted sites before the restoration work (2003) Control Impact 25 Fish per 100m Bleak Brown trout / Sea trout Bullhead Chub Eel Lamprey Minnow Pike Stone loach Species Average species density at control and impacted sites after the restoration (2006) Control Impact 20 Fish per 100m Bleak Brown trout / Sea trout Bullhead Chub Eel Lamprey Minnow Pike Stone loach Species Brown trout / sea trout and bullhead in 2006 declined at all sites. Minnow density increased. Author: D- J Gent 33

34 3.4 Species composition The following diagram shows fish presence and absence at all sites before and after the works. Red shows absence and green shows presence. The fishes most common in the New Forest streams are of brown trout / sea trout, bullhead, eel, lamprey, minnow and stone loach. Pike were also found at two sites that were not restored and bleak were also found at Dames Slough in Author: D- J Gent 34

35 Fish communitry based on Carle and Strub population estimates in 2003 control sites Number of fish Stone loach Pike Minnow Lamprey sp. ammocoete Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey Bleak Anderwood Burley Lodge DS Blackwater Bridge Fletchers Hart Hill Lucas Castle Poundhill Heath Reptillary Warwickslade Woolsfield Site The numbers of bullhead, stone loach and lamprey have increased between 2003 and 2006 but brown trout / sea trout numbers have declined. Fish community based on Carle and Strub population estimates in 2006 control sites Stone loach Number of fish Pike Minnow Lamprey sp. ammocoetes Lamprey sp. European eel Chub Bullhead 100 Brown / sea trout 50 Brook lamprey 0 Anderwood Burley Lodge DS Blackwater Bridge Fletchers Hart Hill Lucas Castle Poundhill Heath Reptillary Warwickslade Woolsfield Bleak Site Author: D- J Gent 35

36 Fish community based on Carle and Strub population estimates in 2003 impacted sites Number of fish Stone loach Pike Minnow Lamprey sp. ammocoetes Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey Bleak 0 Blackensford Dames Slough Dog Kennel Bridge Rhinefield Withybed Bottom Site The numbers of minnow and lamprey increased between 2003 and 2006 but brown trout / sea trout and bullhead numbers have declined. Fish community based on Carle and Strub population estimates in 2006 impacted sites Numbers of fish Stone loach Pike Minnow Lamprey sp. ammocoete Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey Bleak 0 Blackensford Dames Slough Dog Kennel Bridge Rhinefield Withybed Bottom Site Author: D- J Gent 36

37 Number of fish 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Fish communitry % based on Carle and Strub population estimates in 2003 control sites Stone loach Pike Minnow Lamprey sp. ammocoete Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey 0% Anderwood Burley Lodge DS Blackwater Bridge Fletchers Hart Hill Lucas Castle Poundhill Heath Reptillary Warwickslade Woolsfield Bleak Site The percentage composition of eels and brown trout / sea trout reduced between 2003 and 2006 but minnow and stone loach have increased. Number of fish 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Fish community % based on Carle and Strub population estimates in 2006 control sites Stone loach Pike Minnow Lamprey sp. ammocoetes Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey 0% Anderwood Burley Lodge DS Blackwater Bridge Fletchers Hart Hill Lucas Castle Poundhill Heath Reptillary Warwickslade Woolsfield Bleak Site Author: D- J Gent 37

38 Fish community % based on Carle and Strub population estimates in 2003 impacted sites Number of fish 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Stone loach Pike Minnow Lamprey sp. ammocoetes Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey Bleak 0% Blackensford Dames Slough Dog Kennel Bridge Rhinefield Withybed Bottom Site The percentage composition has changed from being dominated by brown trout / sea trout and bullhead to being dominated by stone loach and minnows. Fish community % based on Carle and Strub population estimates in 2006 impacted sites Numbers of fish 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Stone loach Pike Minnow Lamprey sp. ammocoete Lamprey sp. European eel Chub Bullhead Brown / sea trout Brook lamprey Bleak 0% Blackensford Dames Slough Dog Kennel Bridge Rhinefield Withybed Bottom Site Author: D- J Gent 38

39 The national average fisheries length at age sizes are 80mm (1 year old), 150mm (2 years old), 210mm (3 years old), 262mm (4 years old), 307mm (5 years old) and 346mm (6 years old). 5 age classes were present in the restored reaches not including fry. Ages 1-5 were present at the impacted sites in Length frequency for brown trout in Restored 10 Not restored Frequency (numbers of fish) Length mm Author: D- J Gent 39

40 3.5 Biomass Total biomass (g) for brown trout / sea trout at control sites for 2003 and Biomass (g) Anderwood Burley Lodge DS Blackwater bridge Fletchers Hart Hill Lucas Castle Poundhill Reptillary Warwickslade Woolsfield Site Total biomass (g) for brown trout / sea trout at impacted sites in 2003 and Biomass (g) Blackensford Dames Slough Dog Kennel Bridge Rhinefield Withybed Bottom Site At the control sites total biomass decreased between 2003 and 2006 except at Burley Lodge and Blackwater Bridge sites. Biomass also decreased on all impacted sites except at Rhinefield. Author: D- J Gent 40

41 3.6 Growth rates A growth curve for brown trout / sea trout caught on the New Forest 2003 and 2006 surveys. The power distribution curve adheres very closely to the actual data. Length weight relationships of Brown trout in restored and not restored sections of the New Forest from 2006 surveys Restored sites Not restored Power (Restored sites) Power (Not restored) y = 7E-05x R 2 = Weight g y = 6E-05x R 2 = Length mm This shows that the growth curve (length / weight relationship) for brown trout / sea trout were very similar between 2003 and There was no significant difference in growth rates between the two survey years. Author: D- J Gent 41

42 3.7 Scale analysis for age and growth Out of 132 fish scales submitted, only 73 could be aged due to problems with replacement scales - a common problem when ageing brown trout. Of the trout that could be aged, the majority were aged 1+, although fish were present to 4+. An overall mean length at age was provided, with comparison to 4 of the sites. Growth rates on control sites (Anderwood, Woolsfield and Burley) and the impacted site (Dog Kennel Bridge) in 2006 are lower than the 2003 New Forest average and lower than the national species average. The growth at Dog Kennel Bridge (impacted) from (2-3 years age) slowed dramatically. This is not reflected in the national and a 2003 growth rates and therefore could be indicative of stress. This is not attributed to the restoration as Dog Kennel Bridge was not restored until Mean length at age for brown trout in Length in mm Anderwood Woolsfield Burley Lodge Dog Kennel Bridge National average growth rate 2003 New Forest average Age Author: D- J Gent 42

43 3.8 Habitat evaluation and interpretation The HABSCORE methodology assessed the suitability of the in stream habitat for salmonids. It did not take account of water quality or recruitment issues. All fifteen sites were HABSCORED immediately after the fish were processed, recovered and returned in 2003 and Electric fishing was used for the fish population estimates and it should be identified that electric fishing equipment is not designed to catch very small fish (0+) effectively. Therefore it is important to be cautious when interpreting the 0+ brown trout component. HABSCORE is a modelling tool and needs to be interpreted in context of environmental conditions. If an observed value for any one variable contained in the environmental type classes lies outside of the range encountered during the model development then the HABSCORE model extrapolates. These variables are then listed on the bottom of the output results. It is also important to study the 90% (CI) confidence intervals (HQS CI upper and lower) to assess how close the observed density is to the predicted. Appendix 1 lists all the definitions of the HABSCORE reports. The difference between habitat before and after restoration (on impacted sites only) has been reported here. This will indicate how salmonid habitat, has changed through the restoration process. This technique does not assess habitat on a reach or catchment scale but only at a site level. Therefore the increased length of channel as a result of increasing the sinuosity (and therefore increased amount of habitat) is not accounted for within the HABSCORE predictions. The following reports show the HABSCORE outputs, before and after the restoration for four control sites and four impacted sites. Author: D- J Gent 43

44 Author: D- J Gent 44

45 The Habitat Quality Score (HQS) shows the predicted density of salmonids for the habitat observed. At Withybed Bottom (impacted) the predicted density after restoration increased for fry and trout under 20cm and but decreased for larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 45

46 Author: D- J Gent 46

47 At Warwickslade (control) from 2003 to 2006 the predicted density for fry and trout under 20cm increased but decreased for larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 47

48 Author: D- J Gent 48

49 At Burley Lodge (control) the predicted change in density between 2003 and 2006 decreased for fry and trout under 20cm and but increased for larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 49

50 Author: D- J Gent 50

51 At Dames Slough Enclosure (impacted) the predicted density after restoration increased for fry but decreased for trout under 20cm and larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 51

52 Author: D- J Gent 52

53 At Blackensford Lawn (impacted) the predicted density after restoration decreased for fry and trout under 20cm and for larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 53

54 Author: D- J Gent 54

55 At Woolsfield (control) the predicted density change between 2003 and 2006 increased for fry but decreased for trout under 20cm and larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 55

56 Author: D- J Gent 56

57 At Fletchers Water (control) the predicted density between 2003 and 2006 decreased for fry, trout under 20cm and larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 57

58 Author: D- J Gent 58

59 At Rhinefield (impacted) the predicted density after restoration decreased for fry, trout under 20cm and larger trout over 20cm. However, these changes were not statistically significant at the 90% confidence interval. Author: D- J Gent 59

60 The following graphs show the HABSCORE scores for restored sites from 2003 and 2006 with the 90% confidence Intervals (CI) Withybed Bottom Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Withybed Bottom Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Author: D- J Gent 60

61 Warwickslade Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Warwickslade Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Author: D- J Gent 61

62 Burley Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Burley Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Author: D- J Gent 62

63 Dames Slough Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Dames Slough Density per 100m Observed Predicted density Lower CI Upper CI <20 >20 Size group (cm) Author: D- J Gent 63

64 Blackensford Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Blackensford Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Author: D- J Gent 64

65 Woolsfield Density per 100 m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Woolsfield Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Author: D- J Gent 65

66 Fletchers Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Fletchers Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Author: D- J Gent 66

67 Rhinefield Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group (cm) Rhinefield Density per 100m Observed Predicted density Lower CI Upper CI <20cm >20cm Size group 2003 Author: D- J Gent 67

68 4.0 Discussion Monitoring carried out in 2003 identified that the number of fish species caught was lower on the channelised stretches than on sinuous stretches. The channelised stretches studied were the sites earmarked for restoration and the sinuous sites were control sites. As expected the diversity did not change between 2003 and 2006 (post restoration) at the control sites (as no works had taken place). There was no significant difference between years or control and impacted sites. Brown trout / sea trout density at restored (impacted) sites was lower than before the restoration. This is not surprising as fish rescues (for all species) were carried out prior to the work to prevent fish kills. Bullhead density had also decreased at all sites (control and impacted) between 2003 and Individual species density had declined for all species between 2003 and 2006 at control sites except lamprey and stone loach. Individual species density had also declined for all species between 2003 and 2006 at all impacted sites except for minnow. The species most common in the New Forest were brown trout / sea trout, bullhead, eel, lamprey, minnow and stone loach. Pike and bleak were also caught. The species composition has altered at all restored sites although this is not surprising as fish were removed from the stretches prior to the works and not replaced after the work. Whilst some fish are highly mobile and may return quickly, others may take longer to re-establish themselves. Future monitoring will enable long term changes in species composition to be identified. Biomass (g) of brown trout / sea trout declined at all impacted sites post restoration except at the Rhinefield site. Again not surprising as many fish were relocated. The length / weight relationship for brown trout / sea trout had not changed significantly between 2003 and However the 2006 growth rates for trout at both impacted and control site are below average when compared to the Author: D- J Gent 68

69 2003 average for the New Forest and the National Fisheries Standard Growth rate for the species. The growth rate of brown trout at Dog Kennel Bridge between 2003 and 2004 showed a marked reduction in growth rate although this is not attributed to the works. The restoration work at the sites has had no statistically significant affect on the availability of brown trout/sea trout habitat for 0+, <20cm and >20cm long fish using the HABSCORE methodology. In addition the increased sinuosity has increased the length of channel (over 1600 metres in total) and therefore the available habitat. The 0+ component (brown trout fry) were not necessarily suited to being caught effectively using electric fishing equipment and that the HABSCORE model was been run with only one set of survey results. He model predicted increasing numbers of certain trout sizes at certain sites but this was not statistically significant at the 90% confidence interval. Brown trout/sea trout have not recolonised the restored sections to levels that the habitat could predictably sustain according to HABSCORE. This could have been affected by the increased area of habitat resulting redistribution of fish at lower densities. The New Forest LIFE restoration work has altered fish species composition and density, but not diversity between 2003 and Whilst the primary aim of the restoration was not fisheries improvement HABSCORE has predicted some potential benefits for brown trout / sea trout density at certain size ranges through increasing physical channel and hydrological diversity on restored sites (although these are not statistically significant). If the density predictions from HABSCORE are representative of the entire restored sections then the increased habitat available will be beneficial to brown trout / sea trout density and other fish species. Author: D- J Gent 69

70 5.0 Conclusions The most frequent species found were brown trout / sea trout, bullhead, eel, lamprey, minnow and stone loach. Pike, chub and bleak were also recorded. No significant difference in species diversity was identified between 2003 and 2006 and between control and impacted sites. Brown trout / sea trout and bullhead density reduced significantly in impacted stretches before and after the restoration work. Species composition altered in both control and impacted sites between 2003 and At least five age classes of brown trout / sea trout were present in 2006 at control and impacted sites. On average, total biomass (all species) reduced at both control and impacted sites between 2003 and The length weigh t relationships for brown trout / sea trout were not statistically different between control and impacted sites in The density of salmonids was lower than would be predicted for the habitat available at all sites in The restoration work has increased the overall channel length and reestablished sinuosity. This has increased the number of river habitats available. It is predicted to be of benefit to certain sizes of salmonids and fish populations as a whole. The increased physical and hydrological diversity at the sites has stabilised some fisheries habitat (particularly spawning gravel) and has created new habitats that have yet to be fully exploited by fish populations. In May 2006 the fisheries ecology had not recovered to the pre-restoration levels when comparing control and impacted sites. However, fish density at control sites was also lower in 2006 than in 2003 and indicated the high natural temporal variability in fish populations. The response of fish populations would be expected to continue over the next few years. It will therefore be essential to continue to monitor the response of the fish populations within the New Forest in years to come. Author: D- J Gent 70

71 6.0 Further work It is anticipated that the fish composition density will return to pre-restoration levels. Whilst there is evidence of partial recovery it is recommended that this survey be repeated in three years time on the restored (impacted stretches) and a number of the control stretches. References Environment Agency and WRc-NSF Ltd (1999) HABSCORE for Windows. A guide to field survey methods (internal Environment Agency report) Environment Agency (2000) HABSCORE for Windows v3.1. Software operation (internal Environment Agency report) Carle F. & Strub. M. (1978) A new method for estimating population size from removal data. Biometrics 34, Environment Agency (2003) New Forest LIFE 3 Project Sustainable Wetland Restoration in the New Forest, Fisheries Survey Report Environment Agency (2003) New Forest LIFE Fisheries Information and Monitoring Protocol Final Report Version 1.2 Author: D- J Gent 71

72 Appendix 1 HABSCORE evaluation at each site HABSCORE is a system for measuring and evaluating stream salmonid habitat features. It is based on a series of empirical statistical models (which are both species and age specific) relating salmonid populations to observed habitat variables. The outputs generated by the models include an estimate of the expected fish populations (the Habitat Quality Score, HQS) and a measure of the degree of habitat utilisation (the Habitat Utilisation Index, HUI). The latter is only available when quantitative population estimates are available. Both of these statistics are produced for each of five salmonid species/age combinations (0+ salmon; >0+ salmon; 0+ trout; >0+ trout <20cm; and >0+ trout >20cm). Developed as an operational tool by the Welsh Water Authority and (subsequently) the Welsh Region of the NRA, HABSCORE was originally used to evaluate salmonid habitat in upland streams in Wales. Using data collected from over 600 notionally pristine sites, HABSCORE was further developed under NRA R&D Project 338 such that it is now applicable throughout the whole of England and Wales. The development of the models which underlie HABSCORE for Windows or the application of HABSCORE for Windows to fisheries management issues are not discussed in this report. Details on these topics may be found in NRA R&D Note 400 (Wyatt et al., 1995b) and NRA Project Record 338/18/W (Wyatt et al., 1995a) respectively. THE RANGE OF OUTPUTS In addition to reproducing the supplied estimates of the observed number of fish at the site and providing the derived density estimates from these data, the HABSCORE for Windows software also produces the following statistics for each age/size group: HQS values; HQS confidence intervals; Author: D- J Gent 72

73 Ln(HQS); variance of (Ln(HQS)); HUI values; HUI confidence intervals; Ln(HUI); residual variance; and model variance. DEFINITIONS OF OUTPUTS HQS values The HQS (Habitat Quality Score) is a measure of the habitat quality expressed as the expected long-term average density of fish (in numbers per 100m²). The HQS is derived by applying the HABSCORE models to the habitat and catchment features that have been entered onto the software, and assumes that neither water quality nor recruitment are limiting the populations. The HQS is used as an indicator of the potential of the site, against which the observed size of populations may be compared (e.g. through the production of the HUI statistics). HQS confidence intervals The lower and upper 90% confidence limits for the HQS are expressed in numbers per 100m². The confidence limits given should enclose the average observed density for a site on 90% of occasions. The probability of getting an observed average density lower than the lower confidence limit by chance alone is therefore 5%. Ln(HQS) Author: D- J Gent 73

74 This is the (natural) logarithm of the HQS. Many subsequent applications of HABSCORE will require analysis of logged data. Variance of (Ln(HQS)) This is the variance of the logged HQS - a value which may be required for subsequent data analysis. HUI values The HUI (Habitat Utilisation Index) is a measure of the extent to which the habitat is utilised by salmonids. It is based on the difference between the observed density and that which would be expected under pristine conditions (i.e. the HQS). The HUI statistic is a proportion - when the observed density and the HQS are exactly the same, the HUI takes the value of one, whilst HUI values of less than one will occur when observed densities are less than expected. The HUI could be expressed as a percentage, so a HUI of 30% would mean that the observed population is 30% of what would be expected for the given habitat. HUI confidence intervals These are the upper and lower 90% confidence intervals for the HUI, expressed as a proportion. An upper HUI confidence interval <1 indicates that the observed population was significantly less than would be expected under pristine conditions. Conversely, a lower HUI confidence interval >1 indicates that the observed population was significantly higher than would normally be expected under pristine conditions. Ln(HUI) This is the (natural) logarithm of the HUI. Negative values will represent an observed population that was less than which would be expected given the habitat. Author: D- J Gent 74

75 Residual variance This is the variance around the model. It is required when HABSCORE data from a number of sites are combined. Model variance This is the uncertainty in the HABSCORE models, and will become larger for sites that depart from the theoretical average site that was used to calibrate the models during their development phase. It is required when data from a number of sites are combined. Author: D- J Gent 75