WTT Blog Posts

The results are in: barriers down, fish up

I’ve been looking forward to this moment for quite some time now…..well, at least a year. The monitoring of my pet project from pre-intervention (weir notching and removal / partial demolition over six structures) to several years post is quite revealing, and I’ll let the data do the talking.

Now, as a scientist, I know there are a few caveats associated with the figure above. But as there was no specific funding pot for the monitoring of the works for this duration, I am making the best of the situation. So, all surveys were carried out in each of the years for roughly the same amount of time (effort), over similar distances, using similar kit, and roughly the same time of year (although 2018 was a little later because of the incredibly dry spring / summer we have just experienced). Ideally, all of these parameters would have been standardised; ie identical each time.

I only have one year of pre data, and two ‘proper’ years of post, and trout numbers are notoriously variable year to year, but the numbers didn’t fluctuate too much at the reference site (grey bars). I say proper years, as the 15/16 floods annihilated the trout production from that year (I could not find any young-of-year in 2016) and altered the river habitat substantially, maybe even flushing some of the larger trout out of the system. Hence, the dip in 2016 data which was actually when we carried out the majority of the works.

Given the above, where we have removed obstructions to fish passage (blue bars), there are 5x the number of fish in 2018 compared to those same sites in 2015 prior to the works, whereas at the reference site the numbers are at most 2x higher.

I’m fairly confident we’ve had a positive impact just using this simple measure of brown trout abundance, but then the accumulated scientific evidence from all sorts of rivers around the globe is unequivocal! And of course, it's not all about the trout, as the benefits of weir removal spread way beyond fish.

Some folk are still sceptical about aspects though. For example, there is a perception that removing weirs will remove big fish habitat. As my colleague Paul points out in his blog post, unshackling a river from weirs should allow it to recreate over time a natural sequence of pools, riffles & glides where trout of all sizes and life-stages should find a patch to suit their needs. To come back to my project data, in the 2015 survey, the largest trout measured ~320mm. In 2018, there was a considerable number that were >400mm.

That's made my week. Cheers!

Goldilocks weather

What has happened to our young trout during all the recent 'abnormal' weather? It's a question I have heard discussed and been asked directly quite regularly of late, and I intend to post a response with a relatively local flavour, here on the blog, in the not too distant future. However, to pre empt that, I thought I would post some thoughts from my colleague in the south, Andy Thomas. Glaciers were still retreating from Cumbria when Andy first started working on rivers, so he's seen a thing or two....

Please note that this article was originally published in the WTT Summer Newsletter (one of the perks of being a member), and hence was written prior to the extended warm & dry period that subsequently ensued! 

Last year, I resorted to quite a bit of wishing for lashings of winter rain to top-up the chalk.   Well, all I can say is, be careful what you wish for because as we all know, despite dire predictions from pathetic old soothsayers like myself, it started to rain in late February and virtually didn’t stop until we were gripped by the Beast from the East in late March! As Brits and anglers, we like nothing more than to talk about the weather but it is interesting that some of the conditions we crave as fishermen are not always that great for the fish themselves.

Take this last year, for example. A dry, low-flow autumn/early winter, followed by a very wet late winter/early spring. What’s wrong with that? Well, if you happen to be a trout, quite a bit actually!

The main issue with a low-flow autumn might be that adult pre-spawners find it much harder to get to where they need to be. Browns, as well as sea trout, are migratory and upstream progress is so much easier on the back of increased flow. If the headwater and tributary springs haven’t broken on a chalk river system by mid-January, then many fish are forced to cut redds lower down the river system. This often leads to increased competition and over-cutting on sites that have been reduced in size, with potential spawning grounds further up the system left unoccupied, or literally high and dry!

A lovely trout redd on the upper Test in January, clearly visible as the patch of clean gravel in the centre of the shot

Now if that wasn’t bad enough, what happens to those eggs that have been deposited into a favourable location on a nice ramp of loose, clean gravel when it starts to rain and rain and rain? Well, the first thing that happens following months of below average rain-fall is that every field, road, ditch, drain and gulley has months-worth of fine sediment that’s picked up and flushed into the nearest river system.  I always used to think that when chalk rivers morphed from being low and clear, to high and coloured, what I was actually witnessing were sediments being flushed away, leaving sparkling clear gravels ideal for optimum trout recruitment. What I didn’t really give much thought to was the impact of massive volumes of new, highly organic sediments that are flushed from the land into the river and being forced through those areas where tender and highly vulnerable eggs are incubating.

Those who know their spate rivers will tell you how catastrophic a big winter flood can be at the wrong time, with autumn redds being washed away as the bed material literally trundles downstream. Redd washout on low-energy chalk rivers is very rare but what we do know now is that the survival of eggs when exposed to fine, nutrient-rich sediments is very poor. We also know that climate change is highly likely to make our weather patterns even more unstable in the future and it shouldn’t be a surprise for us to learn that an “average” year in terms of water flow and water temperature is going to provide trout with the best opportunities for success. By at least being able to predict what is likely to be a good, bad or average year for trout recruitment might just help to influence some of our management actions.

So, exactly what kind of conditions are going to give trout the best outcomes in terms of recruitment to the next generation? For adult fish to be able to navigate up to unoccupied spawning sites, they will need strong autumn flows, so for chalk rivers that means at least an average previous winter’s rainfall and ideally a wetter than average September and October. These conditions should promote sufficient flow for autumn spawning migrations to be reasonably successful and crucially, should be sufficient to ensure that gravid hens are in the right place at the right time and that the sites selected by the fish for spawning are in good order.

What next? Chalk stream trout tend to spawn later than those of their more northern and western spate-river cousins, although there are chalk stream populations, particularly sea trout which can and do spawn in November. However, spawning for most chalky trout usually takes place between mid-December and mid-January, with frosty weather that pulls down water temperatures often acting as a cue for the start of spawning activity. The drop in water temperature may only be quite subtle on chalk streams where the surface water temperature is heavily buffered by the stable groundwater temperatures, but a short period of high pressure often triggers spawning activity. It is likely that these cues are also linked to dry weather and, therefore, the prospect of increased egg survival when the eggs themselves have yet to harden.

A nice dry, cool and stable December and January, followed by a mild, damp February and March  to recharge the groundwater is what we would dearly love to have. Egg hatching is linked to degree days* and is nature’s way of regulating early emergence from the gravels at a time when there might be little to eat. It seems that a low-flow winter will result in improved conversion of eggs to fry but unless fry and( later) parr habitats are maintained by at least average winter rainfall, then losses to the population described above are likely to occur during their first summer. Heaven knows what a catastrophic drop in water temperature does to newly emerged trout fry, which may well have happened this year following exposure to “The Beast”, but we should assume that it’s probably bad news for fry survival unless those egg sacks have been able to see the bulk of the babies through to a period when the right sized food becomes available as water temperatures climb.


A newly hatched, super-vulnerable trout fry

Roll on a “Goldilocks” year – not too wet, not too dry, not too hot and not too cold.... but just right!

Andy Thomas

*Degree days – a standardised way of describing egg incubation time: a multiplier of time in days and average water temperature. For brown trout, eggs hatch around 420 degree days after fertilisation or 42 days at an average of 10ºC.


Connectivity at Coniston Cold

And so it comes to pass….Coniston Cold weir, which in various forms has been a man-made obstruction to fish passage on the R Aire in N Yorkshire for the past 180 years at least, is no more. Instead, there is now 20.4km of uninterrupted free passage along the Aire and a major tributary.... and all for less than £8k!

Coniston Cold Weir: 19m wide and 1.2m headloss, with a 4m horizontal block-stone apron

I will not reinvent the wheel and spend time here discussing how weirs cause environmental issues. The evidence is abundant and simple to find in the scientific literature, and my colleague Paul Gaskell has recently summarised much of that, here. Then there are global-local events like World Fish Migration Day to raise awareness and I would wager that almost every conservation body involved with river restoration has a hit-list of target weirs on their local patch.

Aire Rivers Trust has been floating the idea of removal of this structure for at least 6 years, as elsewhere in the catchment it is developing a head of steam to tackle the last four significant barriers on the mainstem Aire (via HLF funding in partnership with the EA – Developing the Natural Aire, or DNAire for short). Since arriving in Yorkshire, I’ve been (quite literally) chipping away at many of the smaller but no less significant barriers on several tributaries like Harden Beck in partnership with Aire RT and the EA.

Coniston Cold without the weir, awaiting some spate flow to naturally rearrange all the loosened cobble and gravel

So, how does a project like this finally get off the ground? Kevin Sunderland, Aire RT’s weir guru sent an email to Pete Turner (EA Fisheries Officer) and I because he had finally made headway with the charitable trust that now manages the site. The powers that be could see the environmental benefits to removal and the tenant farmer was also supportive. We met, in a pub, of course.

We thrashed through all the possible scenarios and divvied up the workload. Were there any services associated with the structure, abstraction licences, or potential impacts upon other structures resulting from our plans? Was the weir listed or of cultural significance? How would the river bed be affected, for what distance, and in which direction? What monitoring could we put into place?

With Kevin keeping the landowner liaison up to speed and confirming any requirements from the Council’s Archaeological Unit, Pete set about contacting other components within the EA, notably Claire Bithell in Geomorphology because we needed a full topographioc survey, and finding the relevant people to speak to regarding a service search and abstraction licensing. My job was to manage the project overall, coordinate site visits, assess the integrity of the structure and develop a strategy for the removal with the contractor, as well as draw up all the requirements for a Bespoke Permit from the EA (Risk Assessment, Method Statement etc etc). The latter included specifics on sediment management, any fines arising from the work or resuspended, and so I contacted Hy-Tex Ltd and ordered biodegradable Sedimats to trap those.

Dr Jeoren Tummers & colleague (Durham University) electrofishing below the weir

As a part of the Adaptive Management of Barriers in European Rivers (AMBER) project, Durham University staff were keen to survey the fish population (in terms of species composition and density) both prior to removal and after the river had re-naturalised. The pre-works data suggest that while all species were found both above and below the weir, the numbers and size distribution were very different. I hope that they will provide the details in a separate blog contribution when they have conducted the post-works surveying.

With uncharacteristically dry weather extending to 10 weeks, we were desperate to get a move on! In preparative steps, I removed the three boards in the weir crest notch which focussed all the flow and dried out the remainder of the crest and majority of the apron below. Once we had the bespoke permit in place, we also made some exploratory cuts with a Stihl saw to ascertain whether any metalwork was within the structure; thankfully, not. Diaries were consulted, and D-day was set for the 18th June.

Sedimats in place and the 8-tonne machine on approach....

First steps were to set-up the time-lapse camera, prepare the plant entry point, remove one low branch that would cause hassle for the operator, and install the Sedimats. Then it was a case of shifting some stonework from the apron to create a ramp for the 8-tonne machine to get onto the apron itself, from where work could commence. A pecker was used to demolish the crest material into manageable chunks which could be relocated using a bucket. As the site is on a manufactured bend in the river, the EA Geomorphology team were confident that a point bar would develop on the inside bank (left bank) and hence much of the material arising from the demolition was used to infill the weir scour and top-dressed with formerly trapped cobbles. There did turn out to be a little bit of metalwork, so much of my time was spent scouring and scavenging for pins and small sections of mesh. They say a picture paints a thousand words. The time-lapse video tells the tale of ~36hours in roughly 3 minutes….

Time-lapse of Coniston Cold Weir removal

To summarise the project timeline:

  • The weir was in place for at least 180 years
  • Occasional discussions between the Aire RT and the owner continued for ~6 years
  • Planning the details from receiving a verbal owner agreement = 5 months
  • Bespoke Permit application turnaround = 2 months
  • Removal of weir = 2 days
  • Time to observe a benefit = 4 hours after starting removal, a mighty minnow migration


Minnows migrating through the extended weir notch and ramp under creation, ~4h after starting work

Our work has reconnected 20.4km of river and becks...for the princely sum of just under £8k! 

The actual site is still effectively a rock ramp with an artifically steep, though passable, gradient. Now we have to sit and wait and let nature take its course (as it should) through the loosened cobbles and gravels. As I write this, we’ve had a further 4 weeks of zero rainfall, and so the site looks essentially the same as when we left it. The time-lapse is still in position to await the arrival of some spate flow and record what occurs. In addition, I have set-up a motion activated camera to capture some of the wildlife using the site. So far, it has mostly caught adult and juvenile crows working over the new sediment bar and squabbling over invasive crayfish!


'Wildlife' caught on camera: juvenile crows squabbling over an invasive signal crayfish

I’ll update on the channel development and any other findings in due course. In the meantime, if you have any specific questions, please do not hesitate to contact me.

All about the (sea) trout

Hopefully a few sea trout have found a bit of water (not round here mind) and are starting to return to our rivers at the moment. Fitting then to hand over the blog to Angus Lothian, a PhD student at Durham University (see his first blog here) to reflect on a new network for sea trout research.

Salmo trutta is a truly fascinating ‘species’, with such varying life history strategies and showing large phenotypic plasticity, exemplified by their key characteristic of partial-migration.  It is not yet fully known what drives partial-migration, with a component of a population of trout smolting and emigrating from rivers to sea, and the rest remaining river-resident.  Although the trout has often played second fiddle to Atlantic salmon, recent surges in the interest of trout ecology and biology, and in particular sea trout, has led to a rise in the number of scientists and PhD students researching this field.

As early career researchers, it is important for us put name-to-face, and to share our research with our compatriots to help each other by offering advice and opinions, and to generate the potential for future collaborations.  To enable this, 12 PhD and Masters Students (and one Principal Investigator), from six European countries, specifically all working on sea trout, were invited to meet each other and discuss their research at the Norwegian University of Science and Technology (NTNU) owned Snåsavatn Field Station on the banks of Snåsavatn Lake.

Over two days, we each gave a 30 min presentation about our research.  The projects ranged from acoustically tracking sea trout through Norwegian fjords and Scottish sea lochs, to the influences of metabolism on smolting, genetic differences between neighbouring trout populations, and the impact that weirs and hydropower schemes have on both upstream and downstream migrating trout (sea trout, brown trout, precocious-parr, and smolting juveniles). 

It was not all presentations though.  For many of us, we gained some new experiences, including ice fishing on Snåsavatn Lake, with some of us being lucky to catch some Arctic char.  And to finish the meeting off, we donned our warmest clothes and some reindeer pelts, walked out onto the lake with a sled of wood, and enjoyed sitting around a bonfire with a faint glimmer of the Aurora Borealis above us.

Meetings like these are important in the development of early career researchers.  Not only did each of us come away with a foundation for future collaborations, combining various skill sets to ask the bigger and more complex questions, but we all bonded together, which is vital for any personal advancement in science.

A huge thank you to the organisers and funders of this meeting, especially NTNU, and we are very much looking forward to the next one (destination yet to be determined)!

Angus Lothian (@AngusJLothian)

MSc Research with WTT

I’ve just had the pleasure of hosting two MSc students from Queen Mary University of London (co-supervised with Dr Chris Eizaguirre), partly for the WTT Annual Get Together, and partly to undertake some fieldwork specifically for Charlotte Pike’s project. I alluded to their research projects in a former post and now I have the pleasure of handing over to them to update you.

Charlotte’s project focuses on the use of stable isotopes to determine the success of river restoration. I will be analysing samples from pre and post intervention works against an unimpacted control site on the same river to see how the restoration has affected the ‘architecture’ of the food web. Hopefully it should be more like the control! The intervention works have been carried out by the Ribble Rivers Trust at two locations; Bashall Brook and Towneley Hall. At Bashall Brook, a riparian zone has been created where banks of the river were previously bare; essentially livestock exclusion fencing now removes the impacts of grazing and poaching. This strip of vegetation acts as a buffer to reduce nutrient run-off from farmland, keeps the ground more stable and resilient to flood damage to reduce soil erosion, and provides necessary refuge for wildlife. At Towneley Hall, a partial weir removal and a rock pass re-instates the connectivity of the River Calder allowing fish to move between formerly fragmented habitats. These interventions have been conducted to improve the quality of the habitat at these two sites, and it’s my job to find out what changes have occurred as a result! 

Abbie’s project focuses on investigating the presence of some surprisingly large trout in areas of eastern England. These fish are suspected to be migratory sea-trout due to their large size comparative to other trout in the area. Identifying whether these individuals are in fact migrating to and from marine areas will be important in order to correctly manage migratory passages in these rivers.  Making sure these areas are suitable for migration will also help support the input of these suspected populations to the wider sea-trout stocks.

Eel wrestling - definitiely a two-person job!

Just over a month in - and a lot of reading later – we are definitely feeling more confident with stable isotopes. In short, we are what we eat! When an organism consumes food, it gets integrated into its tissues, producing an isotope signal that we can measure. This signal can be used in a couple of different ways. In Charlotte’s project, it will be used as a proxy for trophic position, from which we can identify any changes at a population or community level in the river and see how organisms have reacted to the interventions. In Abbie’s project, we can use it to get an idea of habitat use across a salinity gradient. This means tracing where our fish are feeding and indicating whether they are resident brown or migratory sea trout. We hope to use fry samples to assess whether sea-trout are spawning in the area because the fry should have a similar isotope signal to their mother ie rather different from fry from parents resident in the river.

We began our journey with a helping hand from Tor Kemp, Jon’s PhD student at QM (and stable isotope whizz), who took the time to help us get to grips with some of the analyses and statistics we would be using in the future. She introduced us to R packages SIBER and MIX-SIAR, so we should be able to analyse our data appropriately - we are extremely grateful!

Grinding (using a v flash agate pestle and mortar) and weighing miniscule samples for mass spectrometry

Over the last month, sample processing has begun including fish dissections and invertebrate preparation. The inverts with calcium carbonate shells had to be separated from those shells to prevent the inorganic carbon affecting the results; some of the fiddly specimens will require acid treatment to remove the smaller parts of shell. Once this has all been carried out, the samples get put into the oven for a few days to dry out. Next steps entail grinding and then weighing on a micro balance (we are routinely weighing out less than 1 microgram!) ready for analysis on the Mass Spectrometer. Sounds easy enough on paper, but this is actually a slow process. However, Abbie is starting to get some results through and we are both looking forward to the coming weeks where we should start to be able to piece together more of a picture! Needless to say, we’re looking forward to the field work!

Download a copy of the poster we presented at the WTT Annual Get Together, here.

Follow our endeavours via @Charlotte_Pike1 & @AbbieNye

A weir'd way to travel

World Fish Migration Day is a biennial event and this year falls upon the 21st April. If you have not heard of it, it’s a global-local event to create awareness of the importance of open rivers and migratory fish. Check out some of the events that are going on around the world - there may be something near to you:


Of course, reinstating connectivity on rivers is a day-to-day challenge for the majority of the WTT Conservation Officers. Paul Gaskell has recently blogged about why we might want to; some of the reasons are fairly hard to ‘see’, even if you spend a considerable amount of your time on or by the water:


Aire Rivers Trust is thinking along the same lines. In a partnership with the Environment Agency, they have just secured significant funds from the Heritage Lottery for DNAire (Developing the Natural Aire), a project which aims ‘to return salmon to Skipton’. And sea trout, of course...and all the other river resident species which need unrestricted access to flourish!

So, where am I going with all of this?

To tie in with World Fish Migration Day, I'm planning a local event on the Aire. I am teaming up with WTT colleague, Tim Jacklin, and we will make our way for over 50km along the river, as a migratory fish would, through the four weirs from Gargrave to Leeds that will be made passable under DNAire. We'll be migrating downstream. Yes, it'll make our lives (slightly) easier, but we think this is important because the issues associated with downstream migration past weirs receive comparatively little press.

We will use a sit-on-top double kayak to allow us to get as close to a fish eye view as possible, with a time-lapse camera on the prow to record the journey. Such a mode of transport will also allow us to view various parts of the river that would not be accessible normally. We will record habitat quality and any detrimental issues which will provide useful information for future Aire RT / Wild Trout Trust / EA project ideas and funding applications to improve the river further.

We appreciate that there are certain tensions between angling and canoeing interests. However, I don’t want the type of vessel we are using to be a focus. The aim is to raise awareness and to do good for fishery and wider ecology interests as a specific, one-off event, sanctioned by all the appropriate authorities and stakeholders. We are hoping to drum up local support at various key points, especially the weirs themselves (Armley Mills, Kirkstall Abbey, Newlay and Salts Mill) and possibly Rodley Nature Reserve where there is already a high-profile fish pass.

OK, so we're doing the hard bit. Over to you to do something too.

Perhaps with your help, we can raise some funding as well to progress further smaller scale but still important barrier removals on rivers and stream all over the UK? Here at WTT we have a ‘Dambusters Pot’! Support us on this aire-brained adventure….we’ll need it! Buy us a virtual round and we promise to do good with it:


And follow our progress on the 21st and 22nd April via Twitter - @ProfJGrey

I've made a timetable of the journey available here, if you are local and want to come and support us

Cheers, Jonny (& Tim)

Reflecting on NoWPaS 2018

Quite a few of our guest bloggers recently have been at the same conference. Unfortunately, I could only follow the key scientific revelations via Twitter from afar but I have been alerted to some work of which I was previously unaware, so I am hoping to establish contact with those people and perhaps they will contribute a blog or two in the near future. Here, Jess Marsh (she of the water crowfoot and salmonid community research) has kindly offered to tell us briefly about NoWPas.

A week after the 14th annual NoWPaS workshop was wrapped up in spectacular style with a traditional Finnish nuotio, or campfire, we are reflecting on an inspiring week of exciting salmonid research, new experiences and friendships.

salmon trout research early career phd

NoWPaS 2018 participants at Oulanka Research Station, Finland. Photo taken by Angus Lothian

For those new to NoWPaS, it is the International (formerly Nordic) Workshop for PhD and post-doctoral fellows working on anadromous Salmonids. This annual event aims to build and maintain an international network of young scientists working on migratory salmonids, including Atlantic salmon and brown trout. Since its establishment in Norway in 2005, the workshop has travelled across Europe, and even made it over to Canada in 2016. Year-on-year, the workshop structure has remained the same, which is testament to its appeal to early career researchers. The week includes short presentations by all delegates, presentations from invited keynote speakers – senior researchers in their fields, excursions to places of interest, and a chance for participants to immerse themselves in local culture and activities.

This year, we were at the Oulanka Research Station of the University of Oulu, in Kuusamo, which is located in the north-east of Finland. En route from our meeting point in Kajaani, we stopped off at the impressive Kainuu Fisheries Research Station in Paltamo, which is one of the largest facilities for fish research in semi-natural and experimental settings in Europe, and is involved in a wide range of projects focusing on salmon and brown trout.

salmon trout research phd early career

Ice fishing in Oulanka National Park. Photo taken by Aurora Hatanpää

This year’s workshop was the biggest yet – 30 delegates and 4 keynote speakers, from 19 different Universities – and so we were treated to a wealth of fantastic talks ranging in subjects from trends in space use by sea trout in Scottish sea lochs to the impacts of increasing temperature on Atlantic salmon populations in Canada. As well as exploring the stunning Oulanka National Park, we tried our hands at ice fishing, snow-shoeing and ice-swimming (post sauna, of course). To top it all off, we even got a display of the Aurora Borealis…

Aurora borealis, Oulanka. Photo taken by Angus Lothian

Huge thanks to the organisers of NoWPaS 2018 for all their hard work putting together a great meeting. We now look forward to March 2019 when NoWPaS will return to Scotland, to the Scottish Centre for Ecology and the Natural Environment (SCENE) at Loch Lomond.

One of the founding and foremost principles of the NoWPaS network is that it is free for all participants to attend. In the past, we have been able to achieve this thanks to generous support and contributions from sponsors. Our fundraising for the 2019 workshop will be kicking off shortly.

There are several ways to donate money, including in-kind donations, equipment donations (that are auctioned) and sponsorship. To learn more about how you and/or your organisation can get involved, please email nowpas2019@gmail.com.

Follow NoWPaS at @NoWPaS

Spot the difference(s)

Gather some fine fishy folk into a room and get them talking (as if you could stop ‘em) about brown trout. How long do you reckon it would be before the topic of colour or more likely spotting pattern would creep in? Let’s face it, we love our spotties! It’s just such an integral part of their beauty and wonderful diversity.

So, for no other reason than the sheer beauty of ‘em, I’m going to ask you good supporters of WTT to snap a few images of wild brown trout spots when you’re out this season but specifically trying to focus on one area – square on and below the dorsal fin. In fact, just like the images scattered around this page, trying to avoid any large patches of glare / reflection / contrast. These images were lifted from 'whole' fish shots, and hence aren't the best quality. I'm hoping you can provide some close ups of the fish flank.

Obviously, fish welfare takes priority here, so I don’t want you to spend ages composing a finely focussed still-life. The good thing about this exercise is that it can be done in the net. I’ll be cropping everything down to focus on the spots.

If you can send them to me at a reasonable resolution size for printing, I'd like to create a map of the UK (and further afield depending upon uptake) to demonstrate how spotting pattern can vary, as a bit of an engagement tool for WTT. Spot the difference as it were! So, I’d need the river or lake name too. But that’s it. Big fish, small fish, all good….

Of course, some of you may have something similar already – and I’d gratefully accept those too.

Tight lines! Jonny


WTT 'twixt research & conservation

The observant amongst you may have noticed and even (hopefully) read the blog I posted from MSc students at Queen Mary University of London after they had completed an electrofishing survey with me as part of a training exercise. Each year, at the same time, a cohort of Freshwater & Marine Ecology students ‘(re)samples’ Woodplumpton Brook where I have been working with Wyre RT to improve the watercourse habitat and connectivity. Well, two of the most recent students were so enthused by the experience and some of the work that I do at the WTT that they have signed up to complete their MSc projects under my supervision and with Dr Chris Eizaguirre (QMUL).

Both of the projects I will outline below have actually been in existence for a while, and both use my academic expertise in stable isotopes. Stay with me! Each is in partnership with other organisations, and so the students will benefit from work experience outside of the purely academic arena, as well as from developing an extended network of contacts which may well be useful further down the line at job-hunting time!

With the Ribble RT, I initiated a project to use stable isotopes to characterise foodweb change at the relatively small scale of a ‘restoration’ intervention; a previous blog gives more details of one site on the River Calder in Towneley Park, Burnley. To determine change in the foodweb in response to the intervention, we need to use a BACI design: Before and After at Control and Intervention sub-sites. Tim Eldridge, with whom I worked on the trout of Malham Tarn (the very first WTT blog), helped out with the initial sampling and field collections prior to any works commencing.

Now, Charlotte Pike (left), a graduate from the University of Portsmouth, will collect all the post works samples from Towneley, and another site on Bashall Brook where a riparian buffer strip has been established on a bank formerly degraded by livestock grazing and poaching. All aspects are funded under the RibbleLife Project (Heritage Lottery).

The other project is to establish whether large trout from watercourses in various eastern counties that are not noted for their trout populations, are actually sea-trout or whether they are simply clever river resident trout eking out an existence, extremely efficiently, under the radar. This is a more convoluted project in terms of the partnership and I’m ably helped out by my colleague Tim Jacklin with this. Various Environment Agency staff have helped to coordinate collections of river invertebrate and estuary invertebrate reference samples, and in addition, are coordinating local anglers to perform a ‘citizen science’ role in catching these large fish. Tough job eh? They make notes on capture regarding length, weight etc, and carefully collect some scales from each fish which we can use for analysis of stable isotopes. This work has emerged from The Welland Sea-Trout Project.

Another aspect to this project is being coordinated by Dr Adam Piper at the Institute of Zoology with help from the Zoological Society of London, Environment Agency, Atlantic Salmon Trust, River Glaven Fishing Association, Norfolk Rivers Trust, and of course WTT. Again, it is a ‘trying to ID sea-trout or not using stable isotope analyses’ type question but specifically looking at the contribution of sea-trout from small streams to the wider stocks. Abbie Nye (right), also a University of Portsmouth graduate, will be taking up this challenge for her project.

Since I covered many of the fieldwork skills that Charlotte and Abbie will require for these projects on the MSc module I contributed to prior to Christmas, they should be able to hit the ground running. Currently, they are receiving some training in London from my PhD student on the statistical packages they will need to analyse the isotope data, and soon they can start processing the pre works samples and learning the dark arts of Continuous Flow Isotope Ratio Mass Spectrometry (!), before moving onto their own samples.

From here on, I’m going to leave updates to them, so watch this space. 

Communities created by crowfoot?

There are few more captivating sights than a river reach swathed in water crowfoot flowers, for what delights might be hidden beneath?  William Barnes (1801–1886) was certainly inspired:

O small-feac’d flow’r that now dost bloom,
To stud wi’ white the shallow Frome,
An’ leäve the clote to spread his flow’r
On darksome pools o’ stwoneless Stour,
When sof’ly-rizèn airs do cool
The water in the sheenèn pool,
Thy beds o’ snow white buds do gleam
So feäir upon the sky-blue stream,
As whitest clouds, a-hangèn high
Avore the blueness of the sky

This humble member of the buttercup family is considered by ecologists as an autogenic engineer: it can change the surrounding environment via its own physical structure. While many people have tried to study where and why water crowfoot grows, especially in relation to nutrients, few have considered how the plant influences the assemblages of organisms around it. Cue Jessica Marsh’s PhD study….

I am working with Queen Mary, University of London’s  River Communities Group and Game & Wildlife Conservation Trust’s Fisheries team to better understand the role of water crowfoot (Ranunculus spp) in southern chalk stream ecosystems. My PhD project will focus on studying the relationships between water crowfoot and the other plants, invertebrate and salmonid communities in chalk streams. Data will be collected from in-river experiments in the River Frome, Dorset to understand how the presence of water crowfoot drives the variability of other flora and fauna.

Wading through high water crowfoot cover on the north stream of the River Frome, Dorset

So, why chalk streams and water crowfoot? Well, unique in the stability of their thermal, chemical and physical conditions, lowland chalk stream habitats are of both national and international importance. Chalk streams sustain a high diversity of flora and fauna including species of conservation concern such as water vole, European eel, and white-clawed crayfish. They also support the important salmonid game fish species, Atlantic salmon and brown trout.

The high biodiversity supported by chalk streams is thought to be due to the presence of water crowfoot family. These macrophytes are the dominant in-river plant species throughout chalk stream catchments and are described as pioneer species for their ability to colonise a variety of habitats.

The presence of water crowfoot subsequently creates habitats for other flora and fauna. The plant greatly reduces water velocity within and immediately down-stream of the plant stands, whilst increasing velocity elsewhere by directing water around its cover, thereby altering flow dynamics within the river. The reduction in flow results in an increase of fine sediments being deposited downstream of the plant structure. This encourages growth of other macrophyte species, such as watercress and starworts, that may otherwise be unable to establish themselves due to a lack of organic material or high flow rates. Conversely, increased flow elsewhere keeps gravels free from fine silts.

Flowering water crowfoot on the River Frome, Dorset. Photo taken by Bill Beaumont.

This results in the creation of more complex habitats within the river which, in turn, is linked to the abundant and diverse invertebrate communities that are present in chalk streams by providing diverse food sources and refugia. For example, the submersed parts of macrophytes provide a large surface area for suspension-feeding invertebrates, such as black fly larvae and certain caddis fly larvae, to attach to and feed on organic particles. The mosaic of macrophyte species provides suitable habitat for many different insects during their larval stage, such as damselflies and dragonflies.

High invertebrate production, in turn, generates large numbers of potential prey for juvenile salmonids, including mayfly and blackfly larvae. The absence of any naturally occurring large substrate in lowland streams for physical shelter also makes submerged macrophytes a fundamental requirement for juvenile salmonids; to reduce energy consumption and provide refugia from predators.


Whilst the importance of water crowfoot in driving diversity in chalk stream ecosystems is acknowledged, existing studies on this family are often limited in duration and physical scale and most previous studies have only encompassed single components such as macrophytes, invertebrates or fish, rather than the whole stream ecosystem.

One aim of my project is to establish patterns in the number of juvenile salmon and brown trout, and diversity and density of invertebrate species in areas with varying amounts of water crowfoot. The first of three years of data on macrophyte cover, substrate structure, and invertebrate and fish communities was collected from sites spread throughout the Frome catchment in 2015. The data were collected during the GWCT Fisheries Team’s annual parr-tagging event, where 10,000 juvenile fish are caught, tagged and released, providing critical population data.

GWCT Fisheries team and volunteers electro-fishing on the river Frome, Dorset during annual parr-tagging

Preliminary results of this initial data collection show a significant, positive association between increasing cover of water crowfoot and an increase in juvenile salmon density, as well as an increase in cover of other macrophyte species. The findings suggest that an increase in water crowfoot cover, to a certain extent, is beneficial to other chalk stream ecosystem components. The next stage of the research will be to explore these correlative relationships through two-year long manipulation experiments. These in-stream studies aim to elucidate the mechanisms behind the patterns discovered by altering existing water crowfoot assemblages and monitoring the effects on juvenile salmon and brown trout densities, invertebrate communities, other macrophyte species, and the interaction between all of these groups.

Collecting an invertebrate sample with a Surber net - an underwater quadrat!

Gaining an understanding of such relationships is essential in order to develop effective river management strategies and to direct successful conservation of chalk stream ecosystems.

Please feel free to contact me if you have any questions, or would like further information on my work

Jess (jmarsh@gwct.org.uk)

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