656 16 Fish Population Survey Report
Total Page:16
File Type:pdf, Size:1020Kb
Fish population summary report River Glen, Lincolnshire 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 Bourne Eau 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. sites. fishing electric all in Dace numbers. be impacting could this so system the in for predators target an easy quite are chub large low, were chub of numbers general in river, the in place taking is recruitment that show been in have fish fish spawned 2016. which of would 95mm was in caught Numbers t of fish a represent would which bracket 470mm the in was caught chub largest The sites fishing electric in all Chub Results Length Frequency wo in present are they and long 20cm and 12cm they Few u Number of fish Number of fish ld represent a fish of around around fish of a represent ld 0 1 2 3 4 juvenile dace were caught during surveying but this is often the case, they tend to favour habitat where where habitat favour to tend they case, the often is this but surveying during caught were dace juvenile can’t 10 15 20 25 30 35 40 45 50 0 5 95 be be caught easily 60 105 65 115 70 125 75 135 80 145 85 155 90 165 and and are 95 175 . 100 185 7 195 years old. old. years 105 underrepresented 110 205 115 215 120 225 235 good numbers. numbers. good 125 245 – 130 255 Upper River and Upper River Bourne Eau Fish Length (mm) Length Fish 135 (mm) Length Fish 265 140 in in fisheries most data sets 275 145 285 150 295 The largest fish caught measured 235mm and and 235mm measured caught fish largest The 155 305 160 315 165 325 170 335 175 345 180 355 185 365 . fish Most between reside 190 375 around 4lbs. The smallest smallest The 4lbs. around 195 385 200 age juvenile range he 395 205 405 210 415 215 425 220 435 225 445 230 455 235 465 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 Kates Bridge, 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.