Fish population summary report River Glen, 2017

This report provides a brief summary of results from recent fish population surveys on the River Glen between Carlby and Surfleet Seas End. The surveys were carried out to assess the health of the river and enable successful management of our principal fisheries.

Tench caught from the Glen at Money Bridge

Originating team Lincolnshire & Northamptonshire Analysis & Reporting Team Author(s) Jake Reeds Date November 2017

Summary • Seven sites approximately 100m each on the Glen system were surveyed between February and November 2017; five of these sites were surveyed using electric fishing, one seine netting and a 12km side scan survey was undertaken on the lower river between Surfleet Seas End and the “Flats” upstream of West Pinchbeck. One electric fishing site was undertaken on the at Mays Sluice in Bourne, with the rest of the drain being side scanned in early December to assess shoaling fish in colder temperatures. • Two of the sites near Waterside Garden Centre were undertaken as part of specific monitoring work for the off channel habitat improvement scheme. • Sixteen species of fish were recorded and a total of 14118 fish were captured; • Pike and dace were the most widespread species, being recorded at seven and six sites respectively. • Roach were the most numerous species and also had the highest biomass.

Site locations

© Environment Agency copyright 2016. All rights reserved. Ordnance Survey licence number 100024198.

Survey results - summary Fish density (fish/100mˉ²) from the upper river electric fishing sites undertaken is shown below along with corresponding size range of fish present. Results from the netting site at Money Bridge on the lower river are given purely in fish numbers due to the data collection method.

DS Fletland US Kates DS Kates DS Mays US Carlby RB Wilsthorpe Mill Bridge Bridge Sluice Brown Density 1.04 0.25 - - 0.1 - Trout Size range 239 – 348mm 185 – 427mm - - 255 -

Chub Density 4.79 0.375 0.47 - 1.3 0.15

Size range 95 – 394mm 420 – 472mm 200 – 243mm - 127 – 296mm 194

Dace Density 9.79 - 7.61 1.11 23.3 9.23 126 – Size range 128 – 238mm - 137 – 196mm 153 – 197mm 62 – 206mm 208mm Eel Density 2.29 0.25 - 0.11 2.4 1.23 262 – Size range 165 – 264mm 275 – 325mm - 310mm 160 – 385mm 557mm Roach Density 0.62 - - - - 58.46 45 – Size range 130 – 138mm - - - - 242mm Pike Density 0.20 0.5 1.11 0.55 1.5 0.30

Size range 195mm 118 – 218mm 169 – 425mm 172 – 394mm 238mm

Tench Density - - - - - 0.30 115 – Size range - - - - - 123mm Gudgeon Density ------

Size range ------

Perch Density - - - - 0.3 -

Size range - - - - 144 – 145mm - BH, MN, STL, 3SS, BH, BL, BL, BH, MN, 3SS, BL, BH, Present BL, BH, MN 3SS, MN RT MN, STL STL MN

Key: Money Bridge 3SS = Three Spined Stickleback Fish Roach 13318 numbers BH = Bullhead Size range 62 – 265mm STL = Stone Loach Fish Tench 9 MN = Minnow numbers BL = Brook Lamprey Size range 358 – 501mm RT = Rainbow Trout Fish Pike 17 numbers Size range 192 – 925mm Common Fish 9 Bream numbers Bleak, Dace, Perch Size range 97 – 142mm present in small numbers

Upper River & Bourne Eau Electric Density:

Fish density per electric fishing site (fish/100mˉ²) 80

70

60

50

40

30

20

10

0 U/S Carlby Wilsthorpe D/S Fletland Mill U/S Kates D/S Kates D/S Mays Sluice Road Bridge Bridge Bridge Brown trout Chub Dace European eels Gudgeon Perch Pike Rainbow trout Roach RBH Tench

Dace made up the majority of fish caught at all sites in Glen throughout the electric fishing sites. Fifteen different species were caught in the upper river sites, this indicates good species and habitat diversity present. The presence of wild brown trout at three of the sites suggests water quality is good enough in the river for successful spawning but the low numbers would indicate a restriction on the population. The smallest fish caught was 185mm, future investigation could look at recruitment rates of fish in the river to see where possible restrictions are.

Roach dominated the catch downstream of Mays Sluice in the Bourne Eau. There is a large shoal of roach present in the lower Bourne Eau towards the pump station, these fish are quite likely to be moving freely between the Bourne Eau and the Glen through the gravity discharge gates upstream of the pump. The side scan results from the Bourne Eau (discussed later on) revealed very few larger fish present, the majority of fish being small. Larger tench are known to frequent the lower river and may well also be actively moving through the gates.

Length Frequency Results – Upper River and Bourne Eau

Chub in all electric fishing sites.

4

3

2

Number of of fish Number 1

0

95

105 115 125 135 145 155 165 175 185 195 205 215 225 235 245 255 265 275 285 295 305 315 325 335 345 355 365 375 385 395 405 415 425 435 445 455 465 Fish Length (mm)

The largest chub caught was in the 470mm bracket which would represent a fish of around 4lbs. The smallest fish caught was 95mm which would have been spawned in 2016. Numbers of fish in the juvenile age range show that recruitment is taking place in the river, in general numbers of chub were low, large chub are quite an easy target for predators in the system so this could be impacting numbers.

Dace in all electric fishing sites.

50 45 40 35 30 25 20

15 Number of of fish Number 10 5

0

85 60 65 70 75 80 90 95

135 230 100 105 110 115 120 125 130 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 235 Fish Length (mm)

Few juvenile dace were caught during surveying but this is often the case, they tend to favour habitat where they can’t be caught easily and are underrepresented in most fisheries data sets. Most fish reside between 12cm and 20cm long and they are present in good numbers. The largest fish caught measured 235mm and would represent a fish of around 7 years old.

Eel in all electric fishing sites

5

4

3

2 Number of of fish Number 1

0

160 265 370 175 190 205 220 235 250 280 295 310 325 340 355 385 400 415 430 445 460 475 490 505 520 535 550 Fish Length (mm)

Most of the eels caught came from the site at , eels were present at Carlby Road Bridge and at Wilsthorpe so they must be migrating successfully over the weir at Fletland and in Greatford. The largest eel in the 555mm length distribution would be a female that would be starting to get to the size where they are ready to begin their seaward migration to spawn.

Roach in all electric fishing sites

20 18 16 14 12 10 8

6 Number of of fish Number 4 2

0

85 45 55 65 75 95

135 185 235 105 115 125 145 155 165 175 195 205 215 225 Fish Length (mm)

The majority of roach from the electric fishing sites at Mays Sluice in Bourne with over 100 roach present, the largest being in the 240mm size range, this would represent an adult fish approaching ten years old. Low numbers of fish under 85mm were caught

Brown trout in all electric fishing sites

1 Number of of fish Number

0

255 185 195 205 215 225 235 245 265 275 285 295 305 315 325 335 345 355 365 375 385 395 405 415 425 Fish Length (mm)

Low numbers of brown trout were caught during surveying throughout sites in the upper river, the largest was in the 425mm size range which would be an adult fish of around 6-7 years old. Hydrology will be a key factor in enabling a healthy trout population in the river, low flows in summer will hamper survival of juveniles and during winter will inhibit conditions for spawning for adult fish.

Length Frequency Results – Lower River, Money Bridge.

2500

2000

1500

Number of of fish Number 1000

500

0

60 70 80 90

100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260

Fish Length (mm)

A large catch of roach was made at Money Bridge in November, these fish would have been starting to shoal for winter, and conditions on the river were clear so they were tightly bunched up for protection. The netting caught the tail end of the shoal but still caught over 13,000 roach. Within the shoal good numbers of juveniles were caught that indicates successful recruitment is taking place in the river. A text book fish population has high levels of juveniles showing good recruitment with numbers tailing off as fish get older and larger as natural mortality reduces their numbers. There appears to be a gap in the roach population between 100mm and 150mm, this could have been down to a poor year in recruitment possible 2-3 years ago. The largest fish caught was 265mm (not represented on the graph above due to the scale above) but that would have been an adult fish over ten years old.

Side Scan survey results: In early November a side scan sonar survey was conducted on the lower part of the river from “the flats” above West Pinchbeck Road Bridge down to the sluice at Surfleet Seas End. This technique allows large shoals of fish to be imaged, showing where they are located and in what kind of number they are present in. By helping to understand where the fish are at different times of year it allows us to locate them and get a better idea of the health of the population.

Side scan image of the bed of the Glen with either bank visible

Image below of Money Bridge

Image below of Surfleet Reservoir

Side scan sonar showed large aggregations of fish in the lower river, there was a large shoal containing roach and some smaller common bream at Money Bridge which is reflected in the large catch when netting it (over 13000 roach). The shoal itself was much larger with the majority of fish taking refuge under the bridge. The day the netting took place there was a match on at West Pinchbeck Road Bridge half a mile upstream, results were very poor. A good catch of specimen tench was taken in the shoal at Money Bridge with nine fish caught, the biggest weighing approximately 5-6lbs. Several specimen pike were also caught following the roach shoal, the biggest being approximately 18lbs.

Results highlight the highly aggregated nature of lowland fisheries nowadays, shoaling in winter is natural but it seems to be more commonplace where habitat is limited. The next large shoal of roach was found downstream of Surfleet Road Bridge. Further shoals were found downstream of the A16 Road Bridge, including around 100 bream, the largest shoal of roach in the river was immediately upstream of Surfleet sluice. Here tens of thousands of roach were present with the aggregation possibly going into six figures. It is likely these fish will move around the system throughout winter, dispersing to feed during turbid conditions on the river and during darkness.

The Surfleet Res stretch of the river, holding a very large shoal of roach when surveyed. These fish may overwinter in this stretch which could offer clubs holding matches a good location to fish. Boats and moorings offering physical structure, appropriate depth and the presence of people nearby seem to be key requirements of overwintering shelter for roach shoals.

The Bourne Eau was surveyed using the side scan in late November, few fish were present. When temperatures are warmer than a large shoal of silver fish can be found in the lower Eau, they may move freely between the Eau and the Glen through the doors. Up at Mays Sluice the flowing water from the sluice creates a short section that holds the fish caught in the electric fishing survey. This is not representative of the whole river. There is little depth left between Bourne and the pump station, heavy siltation has shallowed the river up with only the half mile above the pump offering a useful water level to fish. The sediment present is also helping to drive the large macrophyte growth seen in the summer on the Eau. This is required to be cut via machine sometimes three times a year, large scale sediment removal would benefit costs as this will likely reduce the number of times it needs to be cut. Further investigations into the level of sediment present are needed, it is restricting the fish population present.

Above Mays Sluice the short section of river behind the Anchor Pub was dredged in winter 2016. This has increased the depth in the stretch to an average of 5-6 foot deep. A water quality meter was put in place to assess conditions in there for fish after the dredging. Results from this indicated that the dredging work has had no negative impact on water quality, in fact it has been very good over a dry summer. Five hundred roach and five hundred common bream were stocked into the section in November 2017. This will take place again in 2018, it is hoped that these fish will begin to recruit naturally and begin a sustainable population in the stretch. This would benefit anglers in Bourne as the area can be accessed by all and is walking distance for a large proportion of the population. The location may be further enhanced by working with local charities.

WFD Classification Current WFD fisheries classification for the Lower Glen system ranges from Bad to Moderate over 9 sites undertaken on the river throughout surveying years (2012 – 2016). Classifications should be put in perspective as results can be heavily influenced by fish location and can be missed. These results have partly lead to the move away from netting sites that are likely to produce relatively random fluctuations in the results from standard techniques to using the side scan sonar to help us assess the river. This will help us locate fish in a system where transient fish populations are hard to locate and classify using standard techniques.

Water Framework Directive water bodies with classification status. Sites in water Overall River Water body ID Fish status Reason body status All sites Low species BAD TO GB105031050720 covering lower numbers and low MODERATE MODERATE Glen system densities at sites

Health of fish population • Results from the upper river electric fishing sites are promising, fifteen different species were captured from the sites with dace populations particularly strong in areas off the back of riffles or deeper holes in the bed at places like Kates Bridge and Carlby. Wild Brown Trout are present as well as Eel, which is classed as critically endangered, Bullheads and Brook Lamprey; all of these species are on the BAP (Biodiversity Action Plan) list. • The main restriction on fish in the upper river will always be hydrological. The river depends on groundwater from the Lincolnshire Limestone, as levels drop off during dry periods it negatively affects the river. The Environment Agency runs the water transfer scheme from the via pipeline into the Glen at Essendine; this was turned on in August to supplement flow coming down the river. Without this the river would be in danger of stopping flowing and drying up down to Kates Bridge. The types of fish species present in the upper system will always be sensitive to flow rates, for spawning, for water quality and for creating habitat and refuge. • The lower river does contain good shoals of roach, tench and some carp but locating them as an angler can be difficult and conditions need to be right to catch. Bream haven’t been captured in large numbers in the river for a long time now so further investigation on the river in the future will concentrate on these. Excessive weed growth will always be a problem over summer for years to come, the combination of nutrient rich silt and water combined with low flows make for ideal growing conditions. It remains a river where if you put the time in there are good fish to be caught. • The fish population in the Bourne Eau is being limited by the level of sediment present. There may be future benefits for both flood defence and fish communities in the future from sediment removal.

Improvement work River Glen habitat improvement work: Waterside Garden Centre stretch, Welland Valley Partnership (Partners involved: Environment Agency, South Lincolnshire Fenlands Partnership and Waterside Garden Centre)

In 2017 a habitat improvement scheme was launched on the River Glen downstream of Fletland Mill, this section of river has been heavily modified in the past for flood defence purposes leaving a straight channel with few features or areas of natural habitat. Running behind the garden centre and using land kindly donated by the landowner the scheme added both in channel and off channel improvements that will benefit fish and wildlife in the area. More information is available from the link below: http://www.wellandriverstrust.org.uk/index.php/2882-2/

Possible Improvements to Habitat

There is an area of backwater downstream of Bourne Eau Pump Station that has become overgrown with glyceria. The entrance to it is now blocked but it would offer very beneficial habitat to coarse fish populations during high flow events but also for fry who require shallower areas with complex marginal structure for refuge.

Next survey [Spring / Summer / Autumn 2020].

If you would like to discuss the information presented in this report, please contact: . Jake Reeds, Fisheries Officer, Analysis & Reporting Team, Spalding . 03708 506 506 . [email protected]

Before you go fishing don’t forget: . You must have a valid Environment Agency rod licence and permission from the fishery owner; . You must comply with the fisheries byelaws; . The coarse fish close season (15th March to 15th June inclusive) applies to all rivers, streams and drains in and 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/.