The 2015 river monitoring season gets underway

A guest blog post by Laura

 

This week marks the start of the ‘spring’ ecology sampling season for my team.  Today I was out collecting invertebrates in Upton, Pershore, Evesham and Broadway, in Worcestershire. I catch the creatures using a method called kick sampling. 

In a nutshell I kick around in the substrate and search under stones to look for invertebrates, they are collected in the net then transferred to a tray.

I pick out all the leaves, sticks and stones, checking none contain invertebrates.  The sample is then tipped back through the net, the water drained off and placed in the container.  


Data is then collected on substrate type, surrounding vegetation, width, depth, plant growth etc.  All this has an impact on the site and can affect the biological water quality and hence the type of creatures present.  Data is automatically uploaded onto a database. 


Once back at the lab the sample is preserved in methylated spirit so the it doesn’t degrade.


Each invertebrate has a score; 1 reflects poor (low) water quality and 10 is excellent (high) water quality.   The photo below shows leeches, molluscs and shrimp (I won’t bore you with the Latin names) from Mere Brook. This initially tells me the water quality is average as these species can tolerate heavy sedimentation and low water quality.  

However, the picture below shows a high scoring cased caddis crawling along the container, its case is made from tiny sand grains.

Cased caddis out of its case

Its’ presence shows the watercourse must be good quality.  Just from poking through the sample in the tray I can see lots of species that indicate good water quality.  Once under the microscope our experts can pick out the smaller species, the scores are added up and this gives the site an overall score for biological quality.

 

In the photo below can you spot the difference between the 2 inverts and the sticks? That is what samplers are trained to do.  You need attention to detail in this job!

In Piddle Brook at Pinvin and Seaford there were more high scoring inverts present, mostly different types of cased caddis fly larvae.  In photo below you can see the cased caddis fly larvae has crawled out of its case which is made from sand grains.  Some make a case out of tiny sticks and leaves.


The caddis fly larvae places 2 stones on either side of their case when constructing it that create ballast so it can crawl along the riverbed.  It is able to retreat into its case to prevent fish from eating it.  If it didn’t have ballast it would get swept away into the water column. 

 

I finished the day in Broadway kick sampling the Badsey Brook. Once back at the office, all 3 pairs of waders, trays, nets and gloves were disinfected and hung up to dry.  


This is what we call biosecurity. We take is very seriously as it can prevent the accidental transfer of diseases and invasive species from one waterbody to another.

They’ll be used in the Sud Brook at Gloucester tomorrow when the monitoring programme continues!

Gardening skills to help fish

On Tuesday 25th March representatives from eight angling clubs, from the Shrewsbury area and further afield, met on the River Roden north of Shrewsbury for a demonstration day of river habitat restoration techniques using large woody debris. The day was organised by Environment Agency Fisheries staff in conjunction with the Wild Trout Trust, with the aim of providing representatives from local angling clubs (and partners such as the Severn Rivers Trust) the opportunity to witness and take part in practical demonstrations of techniques, which they could then put to use in future back on their own stretches of river.

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Despite the weather the day was a great success, with 19 attendees treated to demonstrations of various techniques such as pleaching (hinging) of hazel / alder / willow / hawthorn trees alongside the riverbank and also the introduction of brushwood structures to margins of river.

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All techniques have the aim of creating dense cover for juvenile fish species. However, they also have the benefit of improving river bank protection by making it more resilient to erosion. Brushwood gathered from nearby coppicing work and recent storm damage was also utilised, whilst fixing methods included stakes and wire for bundles and also pinning trees with metal bars so they don’t dislodge form the riverbed.

The work will help to trap silt and clean the gravel on the river bed to provide improved trout spawning habitat.

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More habitat days are planned on the River Frome in Gloucestershire and River Leadon in April, again organised by our Fisheries staff and led by the Wild Trout Trust.

Events like these are made possible by the money we receive from fishing licence sales, buy yours here. http://bit.ly/Y0g6pO

!

Fishy health checks in Shropshire

Our fish monitoring programme is now in full swing and our people have been undertaking lots of electric fishing surveys. On Wednesday 18th June we surveyed the River Onny near Onibury in Shropshire.

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Using electric current we surveyed 100m of the River Onny and caught:

127 juvenile Salmon

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18 Brown Trout

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3 Grayling

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2 large eels

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We measured all the fish and removed 3 scales from each salmon and trout in order for them to aged by our Brampton Laboratory.

This is a fantastic result! We counted salmon redds (nests) on this same stretch in October and November last year and saw salmon spawning, redds and dead kelts (fish that have died from exhaustion after spawning).

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The large numbers we caught shows the river in a great health and that not all the redds got washed away by the winter floods.

Staff from the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) joined us and took 30 salmon parr away to check if they have a parasite, Gyrodactylus salaris.

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It is a category one notifiable disease. The parasite has decimated rivers in Norway and CEFAS check each catchment in the UK every 5 years. Luckily no parasites have been found in our rivers to date.

Catching fish in a half mile wide river

On 8-9th May we carried out the bi-annual fish sampling on the Severn Estuary at Arlingham. This is no simple task as not only is the river very wide, it’s also tidal, rising and falling many metres twice a day.

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We use fyke nets. These are like a long narrowing tube with the wide end pointing upstream. Fish swim into the net and can’t escape. They have special attachments in the mouth to prevent otters entering and getting trapped.

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The fyke nets are set at low tide in the estuary channel. After 24 hours the nets are checked and any fish species present are identified, counted, measured and released.

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The dominant species caught were Mullet, Eel and Sea Bass.

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The netting forms part of our WFD (Water Framework Directive) TRAC (Transitional and Coastal) monitoring programme. The data collected allows us to monitor the fish populations of the Severn estuary.

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Spawning salmon spotting in Shropshire

The River Onny is an important river for migratory Salmon, with numerous fish running the river to get to suitable spawning ground in the upper reaches.

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To spawn salmon cut redds, which are shallow excavations in gravel beds, and lay their eggs at the tail end of the redds where the fertilised eggs can grow into alevins in the relative sanctuary of the deep gravel beds.

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The simplest way to determine the amount of salmon that have run the river to spawn is to count the amount of redds that are cut over a set area and time period. This gives us a good idea of how strong the salmon run has been in any one year and therefore how this will relate to year class strength within the existing population.

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On the stretch of the River Onny, from Stokesay to Onibury, that we surveyed last week 10 salmon redds were seen as well as a pair of salmon guarding a recently cut redd. Four dead cock fish and one dead hen fish were seen. This is all part of the natural life cycle as not all salmon make it back downstream due to exhaustion.

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Trout and chips (of the micro variety)

We have lots of weirs in rivers which are used to provide us with flow information which we use to issue flood warnings and control abstractions in times of dry weather. However, these structures can prove difficult obstacles for fish to get over, reducing the lengths of river available to them. We assist fish passage wherever we can and on many structures have built fish passes.

This week we have been carrying out some research into how easy it is for fish to use one type of fish pass. The location was a gauging weir at Bishop’s Frome on the River Frome in Herefordshire.

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The weir has a Hurn baffle fish pass installed. This has slots which are placed in a row straight up the weir face to encourage fish to jump straight up and over the weir. This is a common installation on our gauging weirs as they are gently sloping.
On longer, steeper slopes, the baffle slots go diagonally up the slope so the fish can expend energy, then pause, before going again, all the way to the top.

We commissioned our consultants, APEM, to investigate whether such a design is suitable as an ‘all species’ (chub, dace, roach, trout) fish pass or whether it is trout specific. We have started the investigation by looking at how easily trout can negotiate the pass.

APEM staff electro-fished the River Frome and caught 14 brown trout (all over 150mm). The fish were anaesthetised, and a PIT tag (micro chip) was inserted into the fish. The fish were measured, the PIT Tag serial number recorded against the length and they were released downstream of the weir.

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When a fish passes through antenna loops placed at the top and bottom of the weir, a camera and sensors record the bar code and capture an image of the fish which is recorded on a hard drive.

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Five days after the fish were released 5 have gone over the weir (they were detected by the upper antenna). Strangely those 5 fish include the smallest (188mm) and the largest fish (338mm) that we tagged. The other 9 fish appear to still be nearby as they have been picked up by the lower antenna loop but have yet to make it to the top.

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The antenna loops will remain in place for at least another week to help monitor the movements and behaviours of the fish when confronted with this type of baffle configuration.

An underground river

Parts of the River Frome in Gloucestershire have dried out completely in the last couple of weeks. We’ve had a few reports from people concerned about what’s caused it and whether it will return to its former glory. Here are some answers.

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Not all of the river is affected, but a fair stretch to the east of Stroud, in the Frampton Mansell area is now completely dry.

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The drying out is a completely natural phenomenon. It happens most years, and is the result of the local geology.

The River Frome flows over highly permeable (porous) rock formations such as limestone and sandstones which also make up the principal aquifers in the Stroud area. Aquifers are underground water reserves, bound up within rock formations. Also, in its upper reaches, the River is mainly groundwater fed. As the groundwater table declines in dry periods below the bed of the river it experiences the drying out episodes which we are seeing now. Any flowing water is now beneath the surface! Extensive faulting (cracks and gaps in the rocks) in the area also locally contributes to losses of river water into the underlying bedrock via these features.

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When we get some rain the groundwater level will rise back to the surface and the River will reappear.

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Because the process happens quite slowly fish and insects tend to naturally move away from the drying area and then return once flows return.