Fisheries survey report of the ( to )

Cambridgeshire and Bedfordshire – Fisheries Monitoring Programme 2014

Summary

The River Great Ouse is the forth longest river in the UK at approximately 230 kilometres in length. The Ouse flows through five counties from its source near in before discharging into the Wash estuary at Kings Lynn in Norfolk. This report details the results of our 2014 survey cycle which is conducted triennially in the upper reaches of the watercourse between Newport Pagnell and Bedford. The results from this survey indicate that the biomass and density estimates are lower than that recorded in 2011; however supporting evidence suggests fish populations are perhaps stronger than our current survey data is suggesting.

Fourteen species of fish, and one hybrid, were recorded over the 6 sites surveyed in 2014. Species present were:

Barbel [Barbus barbus] Gudgeon [Gobio gobio] Bleak [Alburnus alburnus] Minnow [Phoxinus phoxinus] Bullhead [Cottus gobio] Perch [Perca fluviatilis] Chub [Leuciscus cephalus] Pike [Esox lucius] Common bream [Abramis brama] Roach [Rutilus rutilus] Dace [Leuciscus leuciscus] Spined loach [Cobitis taenia] European eel [Anguilla anguilla] Stone loach [Barbatula barbatula]

Roach x common bream hybrid [Rutilus rutilus x Abramis brama]

Density and biomass pie charts with percentage values and colour key:

Species density composition (>99mm) Species biomass composition (>99mm)

Density and biomass of individual fish species are calculated using the number / weight of fish in each site and then a mean (average) calculated for the reach, in this case five sites. Density is reported as the number of individuals of that particular species that might be found in 100m2 of the river. Similarly, biomass is the weight, or grams, of that fish species that might be found in the same area.

The average density (number of fish in a given area) of all species >99mm over the six sites decreased from 5.73 Ind./100m2 in 2011 to 4.54 ind./100m² in 2014, a decline of 21%.

Total average biomass (weight of fish in a given area) of all species >99mm also decreased from 792.3 g/100m2 in 2011 to 732.2 g/100m² in 2014, a decline of 8%. Site locations

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 methodology

The sites were sampled using electric fishing methodology, which uses the physiological effect of an electric field in water to attract and immobilise fish. Electrodes, immersed in the water, stimulate a fishes nervous system so that it swims towards the operator, or is unable to swim away, and can be caught. Image 1 shows the typical components of an electric fishing system.

Image 1

In shallow streams it is generally possible to wade upstream within the channel using generator powered equipment towed within a small boat. When rivers deepen or site depth is variable, electric fishing from a boat using generator powered equipment is often the preferred method. The boat is manoeuvred downstream via an electric or petrol outboard engine or on ropes by an operative on either bank controlling the speed, direction and channel positioning.

Stop nets are positioned across the channel isolating the survey site preventing fish from migrating into and out of the survey area. The electric fishing operation is repeated until a 50% reduction in the total number of fish caught has been achieved.

Fish are measured to the nearest millimetre and scales taken for age, growth and other statistical analyses at the National Fish Laboratory in Brampton. Results are reported utilising fish greater than 99mm as this method has been shown to be inefficient below 99mm. Combined survey data

The largest individual fish (mm) and the number of fish caught during the 2014 survey cycle for selected key species.

Barbel Chub Dace Roach Perch Site No. Largest No. Largest No. Largest No. Largest No. Largest Newport Pagnell 15 666 32 493 46 235 156 189 23 252 D/s Ravenstone Mill - - 7 497 21 101 33 227 5 145 Clifton Reynes 1 113 - - 9 130 38 256 5 242 Turvey - - 1 96 9 200 61 244 7 129 Odell 7 136 10 499 33 193 31 216 9 226 Oakley - - 9 448 98 210 121 247 8 145

Roach were the most common fish recorded, with a maximum density estimate of 2.58 individuals for every 100m2 of river surveyed, equivalent to a 57% share of the total population. Dace were subdominant with 10%, followed by perch which contributed 7% to the overall population density.

Mean density of fish (>99mm) from the River Great Ouse (Newport Pagnell to Bedford) 2014

Pike were the dominant species’ by weight with a mean biomass estimate of 280.6g for every 100m2 of river. Chub were subdominant with 171.4g/100m2, followed by roach with a biomass estimate of 161.1g/100m2.

Mean biomass of fish (>99mm) from the River Great Ouse (Newport Pagnell to Bedford) 2014 Historic survey data

Although considerable historic fisheries data has been collected for the River Great Ouse between Newport Pagnell and Bedford, these survey cycles have been subject to change and disruption by environmental conditions such as flooding. For this reason only survey cycles which feature all of the current monitoring sites will be used for analysis which will allow for closer comparison of the dataset. The comparatively new site at D/s Ravenstone Mill cannot be included due to the dataset currently being limited to only two surveys.

It is immediately apparent from the long term dataset, that since 2004 fish populations have been remarkably comparable over successive survey cycles, however these populations appear considerably reduced when compared to the 1988 and 1994 results. These surveys are, unfortunately, not directly comparable to the current dataset as they were conducted in late autumn / early winter and as such may have been influenced by stock migration and aggregation.

A look at species composition shows that the 1988 catch is bolstered by strong representation by dace and is heavily influenced by a catch of over 450 individuals made at Newport Pagnell and a second catch of 228 fish at Clifton Reynes. However; these large catches of dace were not widespread throughout this river reach and data from the 17 other sites surveyed between Newport Pagnell and indicates that the average number of dace at site level was just 48 fish. Site selection used in the analysis of this report has therefore enhanced the mean population of this species significantly. The mean density estimate of this species over the 5 sites used in this report equates to a population of 10.83 ind./100m2 however across this river reach as a whole the mean density of this species was just 2.9 Ind./100m2. The 1994 survey has been similarly influenced by a large catch of bleak. Are these catches artefacts of aggregated stocks?

Unfortunately there is no record of either the environmental conditions at the time of these surveys or the habitat available at site level; both important factors which are routinely captured in current survey cycles, and which would be invaluable in understanding these catches further.

The 2014 survey cycle recorded the highest roach density estimate since 1994, with the data seeming to suggest a far larger population of "catchable" fish present which should provide improved sport for the visiting angler.

Historic density of fish (>99mm) from the River Great Ouse (Newport Pagnell to Bedford) 1988 – 2014 (minus D/s Ravenstone Mill) Site level survey data

Site: Newport Pagnell Survey Date: 29/07/2014

Species density composition (>99mm) Newport Pagnell recorded the greatest species composition and highest population density estimate of the sites sampled during 2014. Roach were the dominant species representing 31% of the total population, with dace subdominant at 20%, followed by chub with 14%. The 2014 survey recorded the highest chub density at this location since 2001 with encouraging, albeit limited, representation by fish of younger year-classes. The 2014 survey also recorded the second highest barbel density to be found at this site, this was also due to to the presence of younger year classes although larger individuals to specimen size were also present. Historic density data comparison

Site: D/s Ravenstone Mill Survey Date: 08/09/2014

Species density composition (>99mm)

Our routine survey site at Ravenstone Mill was last sampled in 2010: however it was apparent that and deep pool areas were reducing catch efficiency and the particularly high banks were a health and safety risks. To mitigate against these issues the site was replaced with an entirely new sample point 500m downstream, (D/s Ravenstone Mill). When the 2014 result is compared to data from the preliminary survey (undertaken in 2011), fish populations are seen to have declined marginally with this loss in density primarily attributed to a reduced numbers of roach and

bleak captured.

Historic species density data comparison

Site: Clifton Reynes Survey Date: 06/08/2014

Species density composition (>99mm)

Roach were the most abundant species present at Clifton Reynes with a total catch of 38 individuals and the largest fish caught measuring 256mm in length. A single juvenile barbel (113mm) was also captured during this survey a species which has been absent since 2007. When compared to the previous survey in 2011, the species composition at this location had declined from eight to five species present, with chub, bleak, gudgeon and tench all omitted since the previous spatial survey. This was a particularly poor result particularly when compared to recent match

catch data which suggests a far stronger fish population to be present.

Historic species density data comparison

Site: Turvey Survey Date: 30/07/2014

Species density composition (>99mm) The 2014 survey found fish populations at Turvey

to be dominated by roach (81%), with perch

subdominant (9%). Chub were absent during the

2014 survey and although the species has generally only been found in low densities this was the first occurrence of this since monitoring commenced in 1988. At the time of sampling fisheries officers recorded submerged macrophyte growth as covering 90% of the site. This may have caused issues with survey efficiency as the extensive beds of water crow foot (Ranunculus sp.) creates difficulties in locating and capturing stunned fish. This will require further investigation: If the site is no longer representative of the channel in the locality and the survey result is compromised then the survey area may need to be relocated. Historic species density data comparison

Site: Odell Survey Date: 12/09/2015

Species density composition (>99mm) Fish densities at our Odell survey site have remained generally low since 1997, the improved 2007 result should be viewed with some caution being at least partly due to poor survey efficiency and a failure to deplete numbers of roach caught which led to an exaggerated population estimate for this species. The most recent survey charts a slight increase in populations (>99mm) recording the highest density estimate since 2007. The chub population at this site consisted of five large individuals (one of which is pictured above) to a maximum length of 499mm and weighing approximately 4lb. There was little representation

from younger year classes with just five juvenile fish recorded. Also present were seven juvenile barbel with the smallest caught measuring 99mm. Historic species density data comparison

Site: Oakley Survey Date: 03/10/2014

Species density composition (>99mm)

The 2014 catch at Oakley was dominated by roach with individuals present to 224mm in length. Dace were the subdominant species with fish to 210mm in length recorded. A large proportion of the dace captured were less than 99mm in length and whilst the inclusion of these juvenile fish is encouraging for future years and evidence of recent recruitment they are not used to derive the site density estimate.

Historic species density data comparison

Length frequency data

Individual fish lengths collected over a survey cycle can be collated to produce a length frequency distribution for the river reach. These graphs can be used to identify a population’s age structure and note potential strong year classes. This report has concentrated on fish above 99mm but these distributions encompass all fish caught. The fishing method used has been shown to be inefficient at catching fish below 99mm in length. The mesh sizes on the landing and stop nets are also too large to allow efficient catches below this 99mm band. Therefore small fish <99mm are underrepresented and their distributions should be looked at with caution.

Dace: although the number of mature adult fish declined marginally in 2014, the number of juveniles present increased significantly when compared to the previous survey in 2011 and may be linked to recent habitat enhancement work.

Dace length frequency data from the River Great Ouse (Newport Pagnell to Bedford)

Chub: when compared to previous surveys the number of juvenile fish (under 99mm) actually reduced in 2014, although the numbers of large, mature adult fish recorded remained relatively comparable.

Chub length frequency data from the River Great Ouse (Newport Pagnell to Bedford)

Roach: the dominance of fish greater than 99mm in 2014 shows successful recruitment to the population. The 2010 survey recorded a particularly strong juvenile cohort with the bulk of fish caught measuring between 55 – 75mm and it seems reasonable to expect that these fish have grown on and persist within the system.

Roach length frequency data from the River Great Ouse (Newport Pagnell to Bedford)

Potential factors influencing fish populations

Morphology:

As with many rivers across the catchment, the River Great Ouse has suffered from historic channel modification having been straightened and overly widened as part of flood risk management activities. This has affected natural rates of erosion and deposition, as well as reducing flow diversity and channel morphology.

Stock displacement:

During periods of low flow sediment can rapidly accumulate smothering spawning gravels, whilst high flows can cause the displacement of fish stocks and loss of juvenile year classes. Barriers to fish migration will act to slow the re-colonisation of these depleted reaches however, the creation of backwater habitat will go some way to alleviate against this issue.

Invasive Species:

One issue potentially affecting recruitment and fry survival within the River Great Ouse may be the American Signal Crayfish (Pacifastacus leniusculus). The signal crayfish is an invasive, voracious predator and once established within a watercourse are known to detrimentally affect the native ecology as they not only consume eggs and fry of fish but also compete with fish stocks by eating invertebrates, a valuable food source. Signal crayfish are also responsible for loss of habitat and bank erosion through burrowing into river banks causing them to collapse and erode, further exaggerating sedimentation issues especially during periods of low flow. All six survey sites recorded the presence of signal crayfish during 2014.

Crayfish burrows River Great Ouse, September 2013 Crayfish burrows River Tove, March 2014

Barriers:

Fish populations are likely to be restricted and fragmented by a number of man-made structures which bisect the channel and may be acting as barriers to fish migration. Addressing fish passage issues at key locations may help to ease fish migration back into the upper reaches of the watercourse.

Sedimentation:

Sediment deposition and compaction of spawning gravels is detrimental in the recruitment of rheophilic fish populations which require fast flowing stretches of clean gravel in which to lay their eggs. If these gravel riffles become choked by an accumulation of fine sand and silt particles due to diminished flows (which would otherwise have been displaced), the possibility of high mortality rates of eggs and larvae increases significantly due to an insufficient through-flow of aerated water. The upper reaches of the River Great Ouse suffer significant areas of livestock poaching. Areas of poached bank were recorded at three of the six sites sampled during 2014.

D/s Ravenstone Mill, September 2014 Clifton Reynes, August 2014

WFD classification

Based on the initial 2009 classification, the River Great Ouse between Newport Pagnell to Bedford is currently at ‘Good’ status for fish, with this classification derived from fourteen sites:

Element 2009 Classification Fish Good Invertebrates Good Ammonia High Macrophytes Not Classified - No Data Dissolved oxygen High pH High Phosphate Poor Temperature High

Site level classification data:

Site 2009 Classification Survey Cycle Reason for Failure Newport Pagnell High 2008 N/A D/s Ravenstone Mill NOT CLASSIFIED, SITE NOT SURVEYED UNTIL 2011 Clifton Reynes High 2008 N/A Turvey High 2008 N/A Odell Good 2008 N/A Oakley High 2008 N/A

Supporting evidence

Angler match catch data is a simple, yet effective way of monitoring trends in fish populations and angling activity. The data is frequently utilised by the Environment Agency as supporting evidence, whilst providing a wealth of information to help develop fisheries for the benefit of both the fish stocks and the angling community.

Olney and Clifton Fishing Association has been providing match catch data from the River Great Ouse around Olney since 2004, whilst more recently, Vauxhall Angling Club has been supplying match data from the Kempston area.

The data collected seems to suggest that since 2005 the average number of anglers participating in matches per year is gradually declining, however, it should be noted that the 2015 data only includes matches up to the 16 August and as such it is reasonable to assume that this figure is likely to increase as the season progresses.

Average number of anglers per match by year from the River Great Ouse (Newport Pagnell to Bedford) 2004 – 2015

The 2011 angling season recorded the highest number of anglers competing in matches on the River Great Ouse (302), with this figure also coinciding with a peak in the actual number of matches held (11). Despite a similar number of matches occurring since 2011, the number of participants has declined.

Number of anglers Vs number of matches on the River Great Ouse (Newport Pagnell to Bedford) 2004 – 2015 The average weight of fish caught per hour between 2004 and 2014 has remained reasonably consistent, recording an average of 254g over the 11 angling seasons. The current 2015 season has already surpassed this figure at 461 grams per hour. The probability of competing anglers successfully weighing-in during a match is also at an all time high (85%) and has steadily been increasing year on year since 2010.

Average catch rates per hour Vs angler success rate from the River Great Ouse (Newport Pagnell to Bedford) 2004 - 2015

Allowing for the 2009 and 2010 seasons which may have been influenced by environmental conditions, the average top three weights has gradually increased since 2004 with this rise possibly attributed to strong recruitment and the presence of more ‘catchable’ sized fish, particularly roach.

Top three recorded weights from the River Great Ouse (Newport Pagnell to Bedford) 2004 - 2015

Similarly to the results of our routine surveys, species composition recorded during matches has not changed noticeably since 2004 with roach the species most regularly caught followed by bleak and then dace. The presence of common bream during matches has been ‘hit or miss’ but this is perhaps unsurprising due to the nomadic nature of the species, meaning that while there will always be “hot swims” the fish may not be resident at the time of the match.

Species composition from the River Great Ouse (Newport Pagnell to Bedford) 2004 - 2015

Habitat enhancement projects

Our Fisheries, Biodiversity and Geomorphology Team (FB&G) have been undertaking enhancement projects on the upper reaches of the River Great Ouse to increase habitat, enhance spawning potential and provide shelter from high flows. These projects include:

1. The installation of large woody debris and faggots which provide crucial overhead cover for fish to utilise whilst alternating flow diversity and scour spawning areas of sediment.

Woad Farm Newport Pagnell (SP88077 44036) Harold Weirs (SP95372 56552) Oakley Back Channel (TL00822 52815) Odell Mill Channel (SP96717 57781) Mill Farm Gayhurst (SP85624 45154)

Woad Farm Newport Pagnell Oakley Back Channel

Odell Mill Channel Mill Farm Gayhurst

2. Redressing known historic gravel riffles with new, clean gravels, to create an optimum spawning substrate to be exploited by rheophilic fish species, such as chub, dace and barbel. The four sites identified for gravel redressing include:

Woad Farm Newport Pagnell (SP87873 44172) Sherington Road Bridge (SP88372 45373) Harold Weir (SP95012 56483) Radwell Road Bridge (SP99959 56595)

Woad Farm Newport Pagnell, during redressing Sherington Road Bridge, post redressing

Harrold, during redressing Harrold, post redressing

Felmersham, post redressing Mill Farm Gayhurst, post redressing

3. Annual maintenance of existing and newly reinstated gravel riffles using high powered water pumps, which jet pressurised water deep into the gravel removing the build up of excessive silt and sediment which inhibits the through flow of oxygenated water, essential for egg and fry development and survival. This yearly process is currently repeated at 8 locations:

Woad Farm Newport Pagnell (SP87873 44172) Sherington Road Bridge (SP88372 45373) Harold Weir (SP95012 56483) Harold Road Bridge (SP95510 56531) Odell Mill Pool (SP96645 57679) Odell Mill Channel (SP96717 57781) Radwell Road Bridge (TL00476 57254) 1km D/s Radwell Road Bridge (SP9995 956595)

Harrold Weir, pre gravel jetting Harrold Weir, post gravel jetting

Radwell Road Bridge, pre gravel jetting Radwell Road Bridge, post gravel jetting

1km D/s Radwell Road Bridge, post gravel jetting Mill Farm Gayhurst, gravel jetting

Odell Mill, post gravel jetting Sherington Road Bridge, post gravel jetting

4. Restoring 130m of previously un-maintained back-channel at Radwell, creating a crucial refuge area for fish to utilise during spate events, particularly juvenile fish which would otherwise become displaced significant distances downstream. Two investigative fish population surveys were organised following completion of the maintenance work, the first in 2012 and the second a year later in 2013, to ascertain if any fish were utilising this valuable habitat. The results of the initial survey, which coincided with a period of high autumn river flows when the main River Great Ouse was carrying excess water, appear encouraging with a considerable number of fish present, predominantly juvenile fish.

Species (13/11/2012) (19/11/2013) Total Minnow 1029 179 1208 Roach 166 66 232 Dace 59 37 96 Chub 39 18 57 Common bream 42 0 42 Bleak 27 6 33 Pike 20 0 20 Perch 7 2 9 3-spined stickleback 2 2 4 Bullhead 3 0 3 Stone loach 2 0 2 Tench 2 0 2 Total 1398 310 1708

Radwell Back Channel, pre habitat enhancement Radwell back Channel, post habitat enhancement

5. Creating fish passage at Ravenstone Mill through a staged lifting of the radial sluice gate. A geo- morphological assessment concluded that there would be minimal risk to bed and bank erosion, with localised erosion expected from cattle poaching and crayfish activity. Throughout the trial period the river levels, geo-morpholical response and the impact on the fish population will be closely monitored. Angling Association and Newport Pagnell Fishing Association have been consulted, and input received from both clubs has been gratefully received.

Stocking data

Since 2010, more than 36000 fish have been stocked into the River Great Ouse and tributaries, with an additional 4300 barbel and 2000 chub due to be re-stocked during winter 2015.

Location Date Species Number Sharnbrook 05/11/2010 Chub 1000 Sharnbrook 05/11/2010 Dace 500 Sharnbrook 05/11/2010 Roach 2000 Radwell 05/11/2010 Barbel 600 Sherrington 05/11/2010 Barbel 600 Sharnbrook 28/11/2011 Chub 250 Sharnbrook 28/11/2011 Roach 250 Sharnbrook 28/11/2011 Dace 500 Sharnbrook 28/11/2011 Barbel 1000 Olney 28/11/2011 Chub 250 Olney 28/11/2011 Roach 500 Olney 28/11/2011 Dace 250 Olney 28/11/2011 Barbel 1000 Radwell 28/11/2011 Barbel 200 Newport Pagnell 28/11/2011 Barbel 500 Odell 19/12/2011 Barbel 625 Harrold 19/12/2011 Barbel 625 Turvey 19/12/2011 Barbel 625 Mill Farm Gayhurst 19/12/2011 Barbel 625 Mill Farm Gayhurst 06/09/2012 Barbel 1400 Newport Pagnell 06/09/2012 Barbel 1400 Sharnbrook 06/09/2012 Barbel 1400 Radwell 06/09/2012 Barbel 1400 Sharnbrook 13/12/2012 Chub 1000 Sharnbrook 13/12/2012 Roach 2000 Radwell 13/12/2012 Barbel 833 Mill Farm Gayhurst 13/12/2012 Barbel 833 Newport Pagnell 13/12/2012 Barbel 834 Oakley Back Channel 25/02/2013 Barbel 250 D/s Sharnbrook Weir 25/02/2013 Barbel 200 D/s Harold Weirs 25/02/2013 Barbel 200 D/s Olney Weir 25/02/2013 Barbel 250 Sherington Bridge 25/02/2013 Barbel 200 Mill Farm Gayhurst 25/02/2013 Barbel 200 D/s Mill 25/02/2013 Barbel 100 D/s Weir 25/02/2013 Barbel 100 D/s Radwell Road Bridge 28/11/2013 Barbel 300 Odell Mill Pool 28/11/2013 Barbel 300 Harrold 28/11/2013 Barbel 300 Newport Pagnell 28/11/2013 Barbel 300 Mill Farm Gayhurst 28/11/2013 Barbel 300 Pinchmill Islands 28/11/2013 Barbel 300 Houghton Trout Stream 28/11/2013 Barbel 500 Houghton Trout Stream 28/11/2013 Chub 750 Houghton Trout Stream 28/11/2013 Dace 2000 Lees Brook 28/11/2013 Barbel 500 Lees Brook 28/11/2013 Chub 750 Lees Brook 28/11/2013 Dace 2000 - 24/01/2014 Barbel 400 Olney 24/01/2014 Barbel 400 Mill Farm Gayhurst 16/12/2014 Barbel 600 Newport Pagnell 16/12/2014 Barbel 600 Harrold 16/12/2014 Barbel 600 Odell 16/12/2014 Barbel 600 Radwell 16/12/2014 Barbel 600

Barbel study by Tea Basic

The aim of Tea’s PHD project is to understand the relationship between the direct threats to barbel, and at what life stages, to assess the success of the EA stocking programme and the requirement / design of juvenile habitat on the River Great Ouse, ultimately producing practical management options that the EA and angling clubs can implement to protect and enhance barbel populations. The following is a summary from Tea basic’s ongoing PHD investigation:

Introduction and aims:

Why study freshwater systems and fish in particular? Freshwater systems are one of the most endangered systems in the world; around 90% of European rivers have been altered in a way by human activities. Today one of the most threatening impacts on freshwater systems and their organisms are: habitat fragmentation (in the River Great Ouse there are numerous barriers which cause great problems for fish migrations), then we have invasive species, (especially in my study I will focus on invasive crayfish). Then we have climate change effects in terms of temperature increase as well as in terms of precipitation patterns change which cause extreme flooding or dry seasons. Also nutrient runoff is a big issue, especially at my study site, where there is a lot of cattle faeces leading to gravel clogging due to siltation that mainly affects spawning habitats.

Thinking of the mentioned issue it’s important to have a good target species that reflects those changes and fish are recognized as the key indicators of ecological status under WFD due to their sensitivity to numerous disturbances, high trophic position reflecting changes in the bottom as well. Also they are long lived organisms, better in reflecting long-term changes compared to other freshwater organisms. Even in my main study area Great Ouse the WFD classification of river quality according to fish populations is not particularly high, and usually falls into moderate or poor level. The other very important thing to consider is the spatial scale. Usually studies deal with small scale that cannot be transferred easily to larger spatial scale where management decisions are made. That is why we are going to try to use smaller and larger scale to capture the underlying mechanism of the changes as well as to be able to understand what is happening at the catchment level. You can see here the small ponds where we are going to do small experiments related to effects of angling bait and stocking under controlled conditions and replicated procedures. Also smaller stream will be surveyed to capture more realistic situation in the nature. And finally using old data we will try to understand the effects of mentioned disturbances at the watershed level of Great Ouse. Talking about old data, it is really important to have an appropriate temporal scale, which we are lucky to have due to numerous data on fish abundance and adjacent data on water chemistry and flow dating back to 1980s up till now. Finally, it is really important to come up with an adequate management plan in terms of stocking and habitat restoration.

The main aims of the project are therefore to understand what has been happening to barbel population in the UK in the past in terms of biotic and abiotic parameters, as well as to try to predict the future consequences of mentioned disturbances. Also understanding the role of habitat quality for the population versus stocking will provide enough knowledge to propose a management plan and enhance barbel population.

What has been done so far:

1. Collection of fish scales and river physico-chemical parameters dating back to 1980s which will be used in assessing the impact of numerous disturbances on target fish. This will involve creating a model in order to identify major parameters (other species, temperature, water quality, flow etc) that are affecting the population. As a proxy for measuring population success we will use growth patterns as they can tell us a lot about fish status in the river due to strong connection between fish communities and their environment.

2. Stable isotope analysis is a valuable tool in assessing the diet of fish as well as the trophic interactions with other species. Depending on the available prey, we can assess what the target species is eating relying on carbon and nitrogen isotopes that can be extracted from the scales. This will be done using small ponds as an experimental unit with replicated procedures as well as in the main river and its tributaries. Here is some preliminary work done on stable isotope that shows how angling bait represent a valuable food sources for barbel. Also the other thing I mentioned is showing the trophic interactions with other species and it seems there is evident niche partitioning between barbel and other species. This will be further investigated in the mentioned ponds under controlled conditions.

3. Stocking as a management tool in enhancing barbel population – using small tributary streams that have been stocked with barbel, we will try to understand their integration into wild communities, in terms of diet and interactions with other species (stable isotope analysis). This is still ongoing.

4. Habitat restoration – looking at the effects of gravel jetting on spawning grounds in the Great Ouse catchment. We will focus on surface and subsurface sediment changes as well as the intra- gravel water chemistry alterations as a function of gravel jetting.

Future plans:

1. Long-term effects of physico-chemical parameters on barbel growth and abundance in the Great Ouse catchment

2. Assess the spawning habitat quality for barbel in the River Great Ouse.

3. Understanding barbel eggs sensitivity to fine sediment accumulation and oxygen depletion (Calverton fish farm).

4. Assess stocking success (survival rates, growth and diet composition).

5. Management recommendations.

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 Analysis and Reporting Officer Chris Middleton [email protected]

River restoration day

The Upper Ouse Fisheries Consultative Association (UOFCA) is holding a river restoration day on the River Great Ouse at Mill Farm Gayhurst (Adams Mill) on the 12 September 2015.

Next survey

Spring / Summer 2017.

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