Fish population survey report The Lower River Cam August 2016 This report provides a summary of results from recent fish population surveys on the River Cam between Cambridge and Upware. The surveys were carried out to assess the health of the river and enable successful management of our principal fisheries. Image 1: The River Cam at Clayhithe Summary Five sites on the River Cam were surveyed by Seine netting between the 15 th and 19 th of August 2016. A total of 3678 fish of thirteen species and one hybrid were recorded. Roach were the most numerous species captured followed by dace. The average density and standing crop estimates derived from the ten sites surveyed equate to 25.24 fish per 100m² and 923 grams per 100m² respectively.
Introduction to Environment Agency fisheries surveys The Environment Agency has a statutory duty to maintain, improve and develop fisheries. Our policy is to do this in a way that maximises the social, recreational and economic benefits arising from the sustainable exploitation of the fish stocks that underpin fisheries. To help deliver this duty, we have a National Fisheries Monitoring Programme (NFMP) to describe the status of our fish populations and inform our fisheries management to meet international (WFD, Eel regulations, ICES reporting), national and local data needs. Sites are regularly reviewed to maintain a representative sample of fish populations and the water body as a whole in order to retain a comparable dataset. Sites designated for the national fisheries monitoring programme cannot be altered, unless there is a valid health and safety concern or there has been a review of policy during the monitoring period. Survey locations Map 1: Survey sites sampled on the Lower Cam Table 1: Site Name Reference Survey Date Length (M) Width (M) Area (M2) NGR Midsummer Common CAM255 15/08/2016 65 26 1690 TL4553959244 Fen Ditton CAM257 16/08/2016 60 30 1800 TL4800060400 Baits Bite Lock CAM258 17/08/2016 60 28 1680 TL4838161707 Clayhithe Bridge CAM260 18/08/2016 80 20 1600 TL5002264244 Ducketts Farm Upware CAM263 19/08/2016 70 28 1960 TL5327369513 2 of 25
Survey methodology Five sites on the River Cam were sampled by Seine netting. Seine netting is our primary survey technique utilised on lowland watercourses where depth and width of the river channel precludes the use of electric fishing. The netting process starts by staff positioning stop nets across the river channel to isolate the survey area and prevent fish from migrating in and out of the site. A 100-meter long seine net is then laid by boat to encircle the entire survey area. The nets are constructed from 10mm knotless mesh, which is relatively soft and helps to minimize fish damage. Floats are attached along the top edge and a lead line along the bottom edge to ensure that the net hangs vertically within the water column. This catching net is then hauled in by hand and fish are removed and retained in floating keep- cages. The netting operation is repeated until a 50% reduction in the total number of fish caught in the first catch has been achieved. The captured fish are measured to the nearest millimetre (to the fork of the tail) and scales are taken from a sub sample of these fish for age, growth and other statistical analyses, which occurs at the National Fish Laboratory in Brampton. Density and standing crop results are derived using Carle and Strub depletion methodology and reported utilising fish greater than 99mm in length as electric fishing methodology has been shown to loose capture efficiency on fish below this length. Numbers and population estimates of juvenile fish and small species such as minnow and bullhead should therefore be viewed as a minimum estimate only. Long-term density estimates are derived from surveys conducted post 1996. Although data is available from surveys conducted prior to this, these early surveys had frequently been conducted during the winter months and therefore results may have been skewed by seasonal distribution of fish stocks (shoaling) which makes these surveys unsuited for analysis with more recent and comparable datasets. Due to this uncertainty, these population estimates are not used to determine the long-term average figure. The 1996 data is of borderline use as this was also sampled later in the year than general and the results at some sites may be influenced by stock aggregation. The survey site at Upware was reintroduced to the survey programme in 2016 to replace the historic site at Dimmocks Cote, which had become difficult to access and to survey efficiently. This means that the monitoring point at Upware does not currently have sufficient data associated with it to allow comparison with the regularly sampled sites. Longterm analysis will therefore be undertaken using just the four routine sites with concurrent datasets and analysis of the Upware data will be conducted at site level only. As the 2016 population estimate at Upware was rather low (0.77 Ind./100m 2 ) the removal of this site for analysis of the long term trend causes the mean density estimate to increase from 25.24 Ind./100m 2 to 31.36 Ind./100m 2. As these two density estimates will be used in different stages of this report this is highlighted to avoid confusion occurring between the two figures. 3 of 25
Results Five sites on the River Cam were surveyed by Seine netting between the 15 th and 19 th of August 2016. A total of 3678 fish of thirteen species and one hybrid were recorded. Roach were the most numerous species captured (3009 Individuals) followed by dace. The average density and standing crop estimates derived from the five sites surveyed equate to 25.24 fish per 100m² and 923 grams per 100m² respectively. Table 2: Total number and largest (mm) fish captured for key species during the 2016 survey. Site Roach Dace Perch Common Bream Pike Number Largest Number Largest Number Largest Number Largest Number Largest Midsummer Common 533 227 48 155 32 271 12 203 1 360 Fen Ditton 1777 263 45 157 71 193 74 192 5 693 Baits Bite Lock 651 189 28 148 113 37 2 176 3 721 Clayhithe Bridge 20 94 27 144 18 106 0 0 1 446 Ducketts Farm Upware 0 0 6 164 11 115 0 0 2 997 Tables 3-4: Density estimate and Standing crop estimate for fish >99mm Table 3 - Results Table for Density (Ind./100m2) Sub Group >99mm Species CAM255 (15/08/2016) CAM257 (16/08/2016) CAM258 (17/08/2016) CAM260 (18/08/2016) CAM263 (19/08/2016) Roach [Rutilus rutilus] 15.56 67.06 20.06 0 0.26 20.59 Dace [Leuciscus leuciscus] 2.78 2.00 1.31 1.63 0.20 1.58 Bleak [Alburnus alburnus] 0.83 1.44 2.38 0.25 0 0.98 Perch [Perca fluviatilis] 0.30 1.61 1.25 0.31 0.15 0.72 Common bream [Abramis brama] 0.65 2.50 0.06 0 0 0.64 Gudgeon [Gobio gobio] 1.72 0.67 0 0 0 0.48 Pike [Esox lucius] 0.06 0.28 0.18 0.06 0.10 0.14 Silver bream [Abramis bjoerkna] 0.06 0.11 0.06 0 0 0.05 Chub [Leuciscus cephalus] 0.12 0.06 0 0 0 0.03 Ruffe [Gymnocephalus cernuus] 0.12 0 0 0 0.05 0.03 Total 22.19 75.72 25.30 2.25 0.77 25.24 Mean 4 of 25
Table 3a - Results Table for Standing Crop (g/100m2) Sub Group >99mm Species CAM255 (15/08/2016) CAM257 (16/08/2016) CAM258 (17/08/2016) CAM260 (18/08/2016) CAM263 (19/08/2016) Roach [Rutilus rutilus] 433.4 1624.6 419.3 0 7.5 496.9 Pike [Esox lucius] 22.6 480.7 366.7 47.0 617.1 306.8 Dace [Leuciscus leuciscus] 82.6 41.0 35.2 38.9 2.6 40.1 Common bream [Abramis brama] 32.0 99.8 5.2 0 0 27.4 Perch [Perca fluviatilis] 52.8 46.3 21.7 5.0 3.4 25.9 Bleak [Alburnus alburnus] 14.5 16.7 31.1 4.4 0 13.4 Gudgeon [Gobio gobio] 32.3 10.9 0 0 0 8.7 Chub [Leuciscus cephalus] 5.0 4.8 0 0 0 2.0 Ruffe [Gymnocephalus cernuus] 3.7 0 0 0 1.5 1.0 Silver bream [Abramis bjoerkna] 1.8 1.9 1.1 0 0 1.0 Total 680.8 2326.8 880.4 95.3 632.1 923.1 Mean Table 4 - Results Table for Density (Ind./100m2) All Fish Species CAM255 (15/08/2016) CAM257 (16/08/2016) CAM258 (17/08/2016) CAM260 (18/08/2016) CAM263 (19/08/2016) Roach [Rutilus rutilus] 32.13 99.67 42.08 1.44 1.58 35.38 Perch [Perca fluviatilis] 2.90 6.28 2.26 1.56 0.56 2.71 Dace [Leuciscus leuciscus] 2.84 2.56 1.67 1.69 0.31 1.81 Bleak [Alburnus alburnus] 1.01 2.56 2.44 0.31 0 1.26 Common bream [Abramis brama] 0.71 4.11 0.12 0 0 0.99 Bitterling [Rhodeus sericeus] 0 3.06 0 0.88 0.10 0.81 Gudgeon [Gobio gobio] 1.95 1.06 0.06 0.38 0 0.69 Pike [Esox lucius] 0.06 0.28 0.18 0.06 0.10 0.14 Silver bream [Abramis bjoerkna] 0.06 0.11 0.06 0 0 0.05 Ruffe [Gymnocephalus cernuus] 0.18 0 0 0 0.05 0.05 Chub [Leuciscus cephalus] 0.12 0.06 0 0 0 0.03 Spined loach [Cobitis taenia] 0 0 0 0.06 0 0.01 Rudd [Scardinius erythrophthalmus] 0 0 0.06 0 0 0.01 Ro x Cb hybrid [Rutilus rutilus x Abramis brama] 0.06 0 0 0 0 0.01 Total 42.01 119.72 48.93 6.38 2.70 43.95 Mean Table 4a - Results Table for Standing Crop (g/100m2) All Fish Species CAM255 (15/08/2016) CAM257 (16/08/2016) CAM258 (17/08/2016) CAM260 (18/08/2016) CAM263 (19/08/2016) Roach [Rutilus rutilus] 598.8 1972.0 588.2 8.4 18.0 637.1 Pike [Esox lucius] 22.6 480.7 366.7 47.0 617.1 306.8 Perch [Perca fluviatilis] 101.9 95.2 33.2 17.0 5.1 50.5 Dace [Leuciscus leuciscus] 83.2 46.4 38.8 38.6 3.4 42.1 Common bream [Abramis brama] 32.5 111.4 5.6 0 0 29.9 Bleak [Alburnus alburnus] 15.8 22.0 31.6 4.9 0 14.9 Gudgeon [Gobio gobio] 35.2 15.1 0.7 3.8 0 11.0 Bitterling [Rhodeus sericeus] 0 18.2 0 5.4 0.2 4.8 Chub [Leuciscus cephalus] 5.0 4.8 0 0 0 2.0 Ruffe [Gymnocephalus cernuus] 4.0 0 0 0 1.5 1.1 Silver bream [Abramis bjoerkna] 1.8 1.9 1.1 0 0 1.0 Ro x C b hybrid [Rutilus rutilus x Abramis brama] 0.8 0 0 0 0 0.2 Rudd [Scardinius erythrophthalmus] 0 0 0.3 0 0 0.1 Spined loach [Cobitis taenia] 0 0 0 0.2 0 0 Total 901.8 2767.7 1066.4 125.3 645.3 1101.3 Mean 5 of 25
Mean density estimate and standing crop by species 2016 Figure 1 displays the mean density estimate derived from the 2016 survey results broken down to species level and shows that Roach were dominant by density with a population estimate of just over 20 Ind./100m 2 (representing 82% of the density estimate). Dace were subdominant with 6% of the density estimate. Roach were present at four of the five sites sampled whilst dace were recorded at all sites, albeit it in much smaller numbers. Figure 2 shows that roach were also dominant by standing crop with a mean population estimate of almost 500 g/100m 2, which equates to 54% of the standing crop. Pike were subdominant representing 33% of the calculated biomass. 6 of 25
Site level density and standing crop by species 2016 Figure 3 shows the considerable variability of stock observed at site level in 2016. Survey site 4641 (Fen Ditton) produced the largest catch of the 2016 cycle with a density estimate of 75.7 Ind./100m 2. Surveys conducted at Midsummer Common and Baits Bite Lock produced more middling results whilst sites at Clayhithe and Upware gave much reduced catches. Figure 4 indicates the dominance of roach in terms of standing crop at two of the five sites, although pike were closely subdominant at Baits Bite Lock and were dominant at Ducketts Farm Upware. 7 of 25
Density estimate of the Lower Cam 1996 2016 Population estimates derived from successive & comparable survey cycles show that the density estimate for the River Cam has been increasing since 2009 (Figure 5) and when the 2016 result is compared to the long-term average it is apparent that the current population is a little higher (Figure 5a). The historic dataset shows that there can be a large degree of variance between survey years with 1996, 2006 and 2008 all producing large catches which, in the case of 2006 and 2007 were not replicated in the following survey cycles which suggests stock migration and aggregation causing these outliers possibly in response to environmental conditions. Figure 5b (overleaf) shows that Fen Ditton has been the most consistent site over the last four survey cycles and Clayhithe has been the least productive monitoring point during the 20-year period this dataset covers. The survey site at Midsummer Common does not seem to be fairing as well as observed in the late 1990 s and early 2000 s although during the 2016 survey fish, including some large chub, were seen a short distance outside of the routine survey area around moored boats and a bridge structure. If fish distribution has altered in response to habitat availability (e.g. cover from moored boats) then this may explain the change in density detected at this site. 8 of 25
Standing crop estimate of the Lower Cam 1996 2016 Whilst density has been steadily increasing since 2009, standing crop has declined since 2010 (Figure 6). This means that the current population is composed of an increased number of fish of a smaller average size. If the 2016 result is compared to the long-term average, it is apparent that the current standing crop estimate is around two thirds of this figure although if the outlier 1996 catch is removed from the calculation the current population estimate is actually very close to the long-term average since 2001 (Figure 6a overleaf). Figure 6b (below) shows the importance of the Fen Ditton site to recent standing crop estimate with this site consistently providing the highest biomass of fish over the past three survey cycles. Baits Bite lock has frequent maintained a much more modest standing crop estimate, however this location was also responsible for the exceptional 1996 result, which comprised of almost 8000 roach and 40 common bream to over 400mm in length. 9 of 25
Site level discussion Site No: 4639 Site name: Midsummer Common Date of survey: 15/08/2016 Species present (All lengths) Minimum Maximum Mean Numbers Species Length (mm) Length (mm) Length (mm) Caught Roach [Rutilus rutilus] 55 227 103 533 Dace [Leuciscus leuciscus] 97 155 132 48 Perch [Perca fluviatilis] 75 271 101 32 Gudgeon [Gobio gobio] 92 128 110 31 Bleak [Alburnus alburnus] 92 136 113 17 Common bream [Abramis brama] 85 203 139 12 Ruffe [Gymnocephalus cernuus] 74 121 104 3 Chub [Leuciscus cephalus] 134 152 143 2 Silver bream [Abramis bjoerkna] 120 120 120 1 Pike [Esox lucius] 360 360 360 1 Rox Cb hybrid 97 97 97 1 Population Composition by density (>99mm) The 2016 survey at Midsummer Common recorded ten species and one hybrid present. Roach were dominant by both density and standing crop contributing a 70% and 64% share of these values respectively. Dace were subdominant and represented 13% of the population density. This current survey cycle found the roach population at midsummer common comparable to the 2013 result, density of this species having steadily increased between 2009 and 2013 although the population remains considerably lower than that recorded in the late 1990 s and early 2000 s. Numerically, the 2016 survey actually recorded the largest catch of roach from Midsummer Common in over ten years, but due to their small size, around half of these fish were not included in the calculation used to determine the current population estimate. Overall fish density at this site has decreased slightly since 2013, primarily due to a reduction numbers of bleak captured. 10 of 25
Site No: 4641 Site name: Fen Ditton Date of survey: 16/08/2016 Species present (All lengths) Minimum Maximum Mean Numbers Species Length (mm) Length (mm) Length (mm) Caught Roach [Rutilus rutilus] 49 263 100 1777 Common bream [Abramis brama] 56 192 114 74 Perch [Perca fluviatilis] 76 193 97 71 Bitterling [Rhodeus sericeus] 51 85 65 54 Dace [Leuciscus leuciscus] 76 157 112 45 Bleak [Alburnus alburnus] 59 121 95 42 Gudgeon [Gobio gobio] 74 120 101 19 Pike [Esox lucius] 423 693 563 5 Silver bream [Abramis bjoerkna] 102 105 104 2 Chub [Leuciscus cephalus] 184 184 184 1 Population Composition by density (>99mm) The 2016 survey at Fen Ditton found roach heavily dominant by density and representing almost 90% of the population estimate. Over 1700 roach between 49mm and 263mm in length were recorded and this was the largest catch of this species during the 2016 survey cycle. Numbers of roach at Fen Ditton have increased over the last few survey cycles and the current population estimate represents the second highest density estimate found at this location since 1996. Common bream represented 3% of the density estimate with 74 individuals between 56mm and 192mm recorded. The current density estimate of common bream at Fen Ditton equates to 2.5 Ind./100m 2 a figure higher than this sites 0.9 Ind./100m 2 long term average 2 and representing the second largest catch of this species at this site, in terms of density, over the last twenty years. 11 of 25
Site No: 4642 Site name: Baits Bite Lock Date of survey: 17/08/2016 Species present (All lengths) Minimum Maximum Mean Numbers Length (IF) Length (IF) Length (IF) Caught Roach [Rutilus rutilus] 50 189 95 651 Bleak [Alburnus alburnus] 95 127 109 41 Perch [Perca fluviatilis] 76 113 100 37 Dace [Leuciscus leuciscus] 92 148 121 28 Pike [Esox lucius] 151 721 511 3 Common bream [Abramis brama] 82 176 129 2 Gudgeon [Gobio gobio] 95 95 95 1 Rudd [Scardinius erythrophthalmus] 70 70 70 1 Silver bream [Abramis bjoerkna] 106 106 106 1 Population Composition by density (>99mm) The 2016 survey at Baits Bite Lock found nine species present with a population density very comparable to the 2013 result (24.9 Ind./100m 2 vs 25.2 Ind./100m 2 ). Although the current population estimate is similar to the previous surveys, species composition is significantly different with roach now dominant by density, replacing bleak, which had been prevalent during the previous three survey cycles. Were it not for the exceptional single catch result made in 1996 (172 Ind./100m 2 ) this current population estimate would be very much an average density result, the long term mean density being 27 Ind./100m 2 (if 1996 data is excluded). 12 of 25
Site No: 4644 Site name: Clayhithe Date of survey: 18/08/2016 Species present (All lengths) Minimum Maximum Mean Numbers Length (mm) Length (mm) Length (mm) Caught Dace [Leuciscus leuciscus] 89 144 121 27 Roach [Rutilus rutilus] 52 94 76 20 Perch [Perca fluviatilis] 64 106 90 18 Bitterling [Rhodeus sericeus] 54 79 67 14 Gudgeon [Gobio gobio] 78 96 90 6 Bleak [Alburnus alburnus] 98 128 114 5 Pike [Esox lucius] 446 446 446 1 Spined loach [Cobitis taenia] 73 73 73 1 Population Composition by density (>99mm) The 2016 survey at Clayhithe produced a density estimate almost twice that of the previous survey, and over three times the one preceding it. Despite this encouraging sounding increase it should be noted that this is still a small catch, with a population estimate of just 2.2 Ind./100m 2. Dace were dominant by density with roach subdominant and while this location should produce a few bites there was little present to interest anglers at the time of survey. With the exception of surveys in 1996, 2006 and 2008 this location has generally produced a meagre catch, although the three survey cycles mentioned previously show that this location can occasionally hold good numbers of fish. This apparent lack of fish is likely due to a localised paucity of habitat, the site lacking cover for fish to utilise. It was also apparent that there was a considerable growth of the non-native invasive plant species Floating Pennywort at this location (although this was not responsible for the poor catch recorded). More information on this plant is included later in this report. 13 of 25
Site No: 4647 Site name: Ducketts Farm Upware Date of survey: 19/08/2016 Species present (All lengths) Minimum Maximum Mean Numbers Species Length (mm) Length (mm) Length (mm) Caught Roach [Rutilus rutilus] 68 137 89 28 Perch [Perca fluviatilis] 53 115 80 11 Dace [Leuciscus leuciscus] 78 104 97 6 Pike [Esox lucius] 630 997 814 2 Bitterling [Rhodeus sericeus] 41 52 47 2 Ruffe [Gymnocephalus cernuus] 118 118 118 1 The survey site at Upware was reintroduced to the survey programme for 2016 to replace the site at Dimmocks Cote, which had become difficult to access and to survey efficiently. There are just three surveys at this site since 1996 and all three have produced small catches dominated numerically by roach and perch. Prior to 1996 two large catches had been made, once in November 1991 and again in 1993, and these were predominantly roach. Prior to this, a survey in February 1989 produced a limited catch comparable to the 2016 result with a small number of roach present. Areas possessing improved habitat such as riparian tree cover and moorings & marinas are present nearby to this site and it is likely that such locations hold a greater fish population than the survey area. The survey area is situated on an area of uniform channel with no specific feature present or reason for fish to shoal in the area. Match results from the Upware area suggests larger fish stocks are present in the locality and good sport is possible when fish are found. The presence of a large pike also suggests plentiful fodder fish in this vicinity, albeit not in the survey area. 14 of 25
Species level discussion Roach were the dominant species in 2016 by both density and standing crop. Figure 7 (below) shows stacked site level population estimates for this species over successive survey cycles and demonstrates the fluctuation of this species at site level over this period. The Midsummer Common site has lost over half of the roach density (>99mm) observed in the early dataset although density at this site had been increasing in recent surveys, and large numbers of younger fish were observed in 2016. Roach populations have also been increasing at Fen Ditton and the current population density estimate at this point is comparable to, or exceeds, that of the early dataset. Roach density at Baits Bite Lock has also been increasing since the very poor 2009 result and the current result is a little above the long-term average (excluding 1996 data). This data also shows how comparatively poor the results have been at Clayhithe with only 1996, 2006 & 2008 survey cycles providing a reasonable catch at this location. Figure 8 (below) shows stacked roach standing crop at site level, again the exceptional 1996 catch is clearly apparent. A declining standing crop is apparent between 2010 and 2016 due to the emergence of a higher density population of composed of a lower average size. The site at Baits Bite Lock bucked this decline and showed a slightly increased roach biomass in 2016. Analysis of scale samples conducted by the National Fisheries Laboratory (N.F.L) found that the roach captured had a maximum age of 11 years old and showed slow growth rates with a percentage standard growth (P.S.G) of 82%. This is slightly slower than the 2013 P.S.G of 84% and when growth graphs are compared it is apparent that whilst in 2013 roach growth increased upon reaching 4 years of age, fish captured in 2016 showed slow growth throughout all age ranges sampled. Slow growth is likely due to the increasing population density and intensified competition for food resource. 15 of 25
Dace were subdominant by density, ranked third by standing crop and were found at all sites sampled. Although the subdominant species dace represented just 6% of the density estimate, such was the overwhelming dominance of roach stocks. Dace were most populous at Midsummer Common and Fen Ditton, and were found to a young population to a maximum of 3 years old. Although unimportant in terms of density Common Bream ranked fourth by standing crop and are a favoured angling species in the River Cam. Common bream were present at Midsummer Common, Fen Ditton and Baitsbite Lock with the largest catch observed at Fen Ditton. Scale reading showed that the common bream exhibited very slow growth with a P.S.G of just 70%, a figure significantly lower than the P.S.G of 90% observed in 2013, which is considered within the normal range for this species. These decreased growth rates suggests that this species is also struggling to find sufficient food resource to reach its full growth potential, however it should also be remembered that this survey only sampled younger year classes and the larger individuals present may not be so pressured by competition from silver fish species. Figure 9 shows common bream density over successive survey cycles and it is apparent that this is a species, which shows considerable variance in catches. The peak year for common bream was 2006 when the species was found at all sites sampled and in higher than average density at three of the four, although the result from Midsummer Common has very wide confidence limits, is based on a poor survey depletion and should be viewed with caution as is likely an overestimation of stock. The survey result from Baits Bite Lock is a different matter and is based on an excellent depletion between catches with over 230 common bream captured averaging between 110mm- 170mm in length. It is then apparent that fewer fish were recorded in 2007, less still in 2008 and in 2009 common bream (>99mm) were not recorded at any of the four sites sampled. Bream are a highly nomadic shoaling species and as such are easy to miss, often resulting in boom and bust catches. Although few larger bream have been caught in recent surveys evidence from matches show that they remain a viable target species with some exceptional catches possible when the fish are located, for example during the summer of 2016 one match recorded weights of 94lb, 72lb and 64lb these being composed chiefly of common bream. 16 of 25
Match Catch database Fish catches by rod and line are a valuable source of information about fishery performance and can be a sound indicator of the status of the exploited stock. The match catch database allows the storage of match results in a way that allows easy analysis of angler catches over time and is a way for anglers to support their fishery and have their say on the quality of sport they are experiencing. The data provided by anglers not only underpins and validates the survey data but in some cases also adds to it by including details of species which have not been caught in surveys. By collecting match catch data an angling club can also know that if it has worries about the state of its fishery, there will be a record of fishery performance against which these concerns may be judged. Recent match catch data is available for the River Cam and the provision of this data by the Cambridge Fish Preservation and Angling Society is greatly appreciated. www.cambridge-fpas.co.uk Table 5, below, gives an example of the angling match results on record for the River Cam since the year 2000. The current dataset is too limited in size to draw any meaningful or detailed comparison, particularly in early years, but it is possibly to make some simple observations on the data gathered from 2016. Year The average weight of fish caught per angler in 2016 was 6lb 6oz at a rate of 1lb 2oz per hour. The average winning weight was over 26lb. Anglers will also be pleased to know that dry nets were a rarity with 96% of those who fished weighing in at the end of the match. Number of matches Number of anglers Number of anglers weighing in % weighing in Total weight caught Sum Hours Fished Weight per angler Weight per hour 2000 1 55 55 100 433-9-15 275 7-14-2 1-9-3 2004 8 332 327 98 1170-4-4 1660 3-8-6 0-11-4 2005 3 56 56 100 343-14-12 280 6-2-4 1-3-10 2006 2 52 40 77 164-3-12 260 3-2-8 0-10-1 2007 4 26 24 92 329-0-4 130 12-10-7 2-8-7 2013 2 28 26 93 94-9-8 140 3-6-0 0-10-12 2014 3 35 31 89 110-15-7 175 3-2-11 0-10-2 2015 4 94 86 91 733-9-9 564 7-12-13 1-4-12 2016 6 95 91 96 607-1-15 538 6-6-4 1-2-0 Year Back up rate total first weight Total second weight Total third weight Average first weight Average second weight Average third weight 2000 1-3-0 59-13-15 38-6-0 25-5-15 59-13-15 38-6-0 25-5-15 A 2004 0-9-10 111-6-15 72-12-15 58-8-15 13-14-13 9-1-9 7-5-1 A 2005 0-15-8 44-2-8 38-8-15 33-0-15 14-11-8 12-13-10 11-0-5 A 2006 0-8-7 17-10-15 14-13-0 9-10-15 8-13-8 7-6-8 4-13-7 A 2007 0-7-13 216-4-0 62-8-0 16-0-0 54-1-0 15-10-0 4-0-0 A 2013 0-8-5 14-1-15 12-5-0 10-8-0 7-1-0 6-2-8 5-4-0 A 2014 0-5-4 29-13-15 21-0-8 17-0-7 9-15-5 7-0-2 5-10-13 A 2015 0-14-0 125-8-15 92-6-8 84-0-8 31-6-4 23-1-10 21-0-1 A 2016 0-12-15 158-12-15 90-5-15 61-15-0 26-7-7 15-0-15 10-5-2 A River class Details can also be retrieved for individual matches and this will provide information on species level presence. This can be useful for highlighting the presence of shoaling species or low density populations which may be missed by surveys, for example, only one tench has been caught at Fen Ditton during routine surveys (in 2002) whereas match catch data shows that this species has been captured at this site as recently as 2016. If other clubs fishing the River Cam wish to provide such data for analysis and inclusion in subsequent reports then this is encouraged and will be welcomed. A blank match return form & instructions are included at the rear of this report. 17 of 25
Conclusions The 2016 survey from the River Cam provided very much a middle of the road result, with nothing particularly outstanding, but when examined a whole, on par with the rivers long-term density estimate. Stock density has increased over the past three survey cycles although the average size of fish is falling and roach and common bream are showing slow growth. Match results show anglers continue to find fish and some excellent results have been had when river conditions were suitable. There have been no concerns raised over the quality of the fishing via the Lower Ouse Angling Consultative. Anglers could help provide a clearer picture of the quality of angling available on the River Cam if more clubs provided match catch results. Management Options: The ARIS acoustic Camera is an imaging sonar capable of creating detailed underwater images in completed darkness or turbid conditions using high frequency pulses of sound and when mounted on a boat this technology can allow long river lengths to be covered, locating fish stocks present and in some cases also identifying the species. Images 2 & 3 below show examples of footage collected by the EA using the ARIS camera and show a large shoal of roach (Image 1) and two large common bream (Image 2) the latter clearly identifiable by the shape of the acoustic shadow. It is suggested that the ARIS camera could be used at Clayhithe and Upware to test the supposition that improved fish stocks are present nearby where habitat of increased complexity is present. The ARIS camera could also be utilised to investigate the whereabouts of shoaling species such as common bream, which are only occasionally captured during routine survey. Image 3: Roach on the River Delph. Image 4: Two large common bream 18 of 25
Non-native species Floating Pennywort: In its native range, floating pennywort (Hydrocotyle ranunculoides) occurs in slow-flowing warm and nutrient rich water in Argentina, Brazil, Paraguay and southern states of the USA. It is an invasive weed in North Western Europe and was first naturalised in the UK in 1990 as an introduction from garden ponds. Since then it has become widespread in the south and east of England and is spreading rapidly north and westwards. Floating pennywort is found in and around canals, lakes, rivers, streams, ditches and ponds. It roots along waterbody margins, growing up to a rate of 20cm per day, and spreads out onto the water as dense interwoven mats above and beneath the surface. These dense mats can quickly overwhelm a waterbody and impede water flow. Very large infestations may interfere with navigation, prevent angling access and increase the risk of flooding. Another important consideration is the detrimental effect of floating pennywort on native plant and animal species. The dense growths result in native plants being shaded out and may obstruct native air-breathing insects from reaching the water surface. In addition, the water beneath mats can become deoxygenated resulting in fish mortality and changes to the invertebrate community. On the River Cam catchment, floating pennywort has been identified from Byron s Pool downstream to the confluence with the Ely Ouse, the lower end of Bourne Brook (from the M11 bridge to the confluence) and in several small tributaries of the main river. Since 2015, the Environment Agency have been working in partnership with the Cam Conservators to undertake control of the floating pennywort in order to maintain navigation, recreation and amenity value. Floating pennywort is usually spread by vegetative propagation, with very small fragments of the plant able to form new colonies. Landowners are responsible for undertaking swift and effective action to control floating pennywort on their land. Under the provisions of the Wildlife and Countryside Act (1981) it is illegal for landowners to allow floating pennywort to spread from their property. Anglers should adhere to the check, clean, dry protocol to help avoid spreading this plant on their equipment such as landing nets and keep-nets. Anglers using weed rakes should be particularly careful not to disturb or break up clumps of pennywort as this could cause the spread of fragments, which may then root elsewhere. If you think you have found floating pennywort please report it to anglian-invasive@environment-agency.gov.uk providing a photograph and detail of the location, preferably including a grid reference. Owners of smartphones could also help track the location of non-native species by using either the Plant Tracker or Aqua Invader Apps available for both Android and IPhone. For more information, please see: http://www.nonnativespecies.org/checkcleandry/biosecurity-for-anglers.cfm 19 of 25
Image 4: Floating pennywort. Image 5: Floating pennywort showing detail of leaf structure. 20 of 25
Habitat enhancement & projects On the nearby Sheep s Green (See map 2 below), a project is underway to enhance the Sheep s Green Stream a small channel that crosses the Local Nature Reserve. This project will have multiple benefits and outcomes, enhancing inchannel habitat for the advantage of fish and invertebrate species and create a bypass channel to allow movement of fish stocks into the River Cam upstream of Silver Street past the weir structures that bisect the river and block, or severely limit, upstream migration at this location. The fish pass proposed at Sheep s Green has the following key components: The existing culvert will be used to bring water from the river to the upstream end of the fish pass and the existing sluice gate in this culvert will be removed. A new flow control structure will be installed downstream of the downstream end of the culvert. This will be comprised of an automatic sluice and a separate deep notch. Downstream of the flow control structure is a large pool, which will act to dissipate the energy of water flowing through the flow control structure. The remainder of the fish pass structure will be a rock-ramp / natural channel comprised of two flights a resting pool in between. Investigative fisheries monitoring has shown that the channel is already utilised by thirteen fish species (data provided as table 6 below), which included a large number of juvenile fish, all of which will benefit further from the improved habitat this project will bring. The fish pass should be installed by the end of March 2017. Table 6 - Sheeps Green Stream results table for numbers of fish caught All Fish Species US Causeway Bridge DS Causeway Bridge (24/03/2016) (24/03/2016) Total Minnow [Phoxinus phoxinus] 59 66 125 Roach [Rutilus rutilus] 1 97 98 Dace [Leuciscus leuciscus] 9 49 58 Chub [Leuciscus cephalus] 4 15 19 3-spined stickleback [Gasterosteus aculeatus] 3 14 17 Bullhead [Cottus gobio] 2 15 17 Gudgeon [Gobio gobio] 2 13 15 Perch [Perca fluviatilis] 0 10 10 Spined loach [Cobitis taenia] 4 5 9 Stone loach [Barbatula barbatula] 5 2 7 10-spined stickleback [Pungitius pungitius] 0 1 1 European eels > elvers [Anguilla anguilla] 1 0 1 Pike [Esox lucius] 0 1 1 Total 90 288 378 21 of 25
Graphs showing growth rates for key species Figure 10: Roach growth rate 2016 Figure 11: Common bream growth rate 2016. 22 of 25
Additional information If any angling matches are held throughout this river length then angling clubs are encouraged to provide match results to feed into the Environment Agencies Match Catch Database which analyses angler catches to assess fishery performance. The output of this database can also be used as supporting evidence to assist analysis of routine survey results. Match return cards and more information on the Match Catch Database can be obtained from Fisheries Biodiversity and geomorphology (F.B.G) Officer Chris Middleton. chris.middleton@environment-agency.gov.uk For information regarding the Fisheries Improvement Programme please follow the link below: https://www.gov.uk/government/news/fisheries-projects-needed-to-improve-the-environment For information regarding the Angling Improvement Fund (AIF) administered by the Angling Trust, please follow the link below: http://www.anglingtrust.net/landing.asp?section=1094§iontitle=angling+improvement+fund Before you go fishing don t forget: Environment Agency rod licence and permission from the fishery owner; fisheries byelaws; Wales but not most stillwaters. Stillwater fishery owners can still have their own close season and rules, so please check with them before setting out. Report illegal fishing: If you see any fishing, netting or trapping you think may be illegal, please do not tackle it yourself. Call us immediately on 0800 80 70 60 and tell us: Exactly where the alleged offence is taking place; What is happening; How many people are involved and their descriptions & The registration numbers of any vehicles involved. If you prefer to remain report an environmental crime anonymously call Crimestoppers on 0800 555 111 or https://crimestoppers-uk.org/give-information/give-information-online/. Justin Mould Fisheries Analysis and Reporting Officer 23.01.2017 Carle, F. L. & Strub, M. R. (1978) A New Method for Estimating Population Size from Removal Data. Next survey due Spring / summer 2019 23 of 25
Environment Agency Match Record (Please complete after each match and return by email to chris.middleton@environment-agency.gov.uk) Name of angling club: River: Section / peg fished: Match start time: Date of match: Venue: Number of competitors: Match duration (hrs): Number of anglers weighing-in: Total weight caught: Winning weight: (lbs/oz) or (g) delete as appropriate (lbs/oz) or (g) delete as appropriate 2 nd weight: (lbs/oz) or (g) delete as appropriate 3 rd weight: (lbs/oz) or (g) delete as appropriate Species Caught In: Greatest number: Second greatest number: Other species present: River Conditions: Level Colour Condition River Temp Low Clear Falling Cold Normal Coloured Steady Normal High Green Rising Warm Weather Conditions: Brightness Wind Rain Dull Still Dry Changeable Light Drizzle Bright Moderate Light Strong Heavy Hail Sleet Snow Any other comments: 24 of 25
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