WTT Blog Posts

Land and lake interconnectedness

On a day-to-day basis, most of my time as WTT Research & Conservation Officer is devoted to river habitats, but in my academic role at the Lancaster Environment Centre, lakes are a long-standing focus of my aquatic ecology research. A Natural Environment Research Council grant allowed a colleague from Cambridge and I to convene a workshop with scientists from Canada, the USA and Sweden, with common interests in how lake food webs may be fuelled by subsidies from the land. The output from that meeting is a recently published synthesis based upon data from ~150 northern lakes. Most of the planet's freshwater lakes and rivers that we associate with various ecosystem services, like fisheries and water supply, are found in the northern hemisphere, a region that is changing rapidly in response to human activity intertwined with shifting climatic trends.

The classical view of lake food webs is that of algae produced via photosynthesis forming the food base for zooplankton (such as water fleas or Daphnia) that is then munched by fish. We do not contest this because algae are typically a very high quality diet, and many lakes contain plentiful algae. However, in lakes that do not contain adequate supplies of such a resource, or during winter when it is less available or completely unavailable, then organic matter from the land, derived from the breakdown of terrestrial plants, can still be used via intermediary bacteria. And this situation is more common than you might imagine.

Our team used stable isotope techniques as natural ‘tracers’ of diet and analysed over 550 zooplankton samples from lakes across a range of conditions from the boreal zone to the sub-tropics. In half of the zooplankton samples, these tiny animals comprised at least 42% terrestrially-derived material. In some instances, terrestrial food sources accounted for up to 83% of total zooplankton biomass.

By concurrently investigating how physical characteristics of the land draining into lakes influenced the observed terrestrial subsidies in the lake food webs, we could identify certain key determinants. Differences in tree cover, vegetation density, soil carbon concentrations, lake area, and lake perimeter can all potentially impact upon the amount of terrestrial matter available to aquatic life.

These widespread findings further highlight the interconnectedness of ecosystems. But they also convey an important message for those tasked with conserving and managing freshwater resources. We must understand how landscape changes, such as forest clearing or reinstatement, or agricultural practices, impact upon lakes that they adjoin or are linked to via river networks.

What does this mean for trout? Well, trout are renowned for their ability to maintain higher populations than we might expect for a given stretch of river or area of lake. That is because they can and do readily tap into food resources from ‘outside’ of the waterbody, i.e. daddy long-legs or heather flies, worms, even cicadas, mice and lemmings. However, if some of their ‘aquatic’ food is already heavily subsidised by terrestrial matter, then it is even more important for us to consider sensitive land management beyond a riparian buffer strip.

The full article for those that are brave, is available open access here: http://advances.sciencemag.org/content/3/3/e1601765

Impacts of low flows on salmonid river ecosystems

In the first of a new series from students actively involved in research relevant to wild trout, Jessica Picken from Queen Mary University of London summarises the aims of her PhD working with the Game & Wildlife Conservation Trust and with CEFAS.

Climate change is considered to be the most critical disturbance imposed on natural systems on a global scale. Climate models predict that average temperatures in the UK will increase over the course of the next 50 years with the greatest warming in the south of England during summer months, and that annual average precipitation will reduce. However, the reduction in precipitation is expected to be more pronounced during summer than winter, whereas extreme winter precipitation is expected to become more frequent. In other words, there is likely to be an overall shift towards drier summers but wetter winters.

River itchen jess pickens qmul gwct cefasFlow regime is widely recognised to be the master variable controlling a number of key riverine processes, including levels of dissolved oxygen, sediment transport and deposition, water quality, and habitat type and distribution. These processes in turn influence the spatial and temporal distribution and abundance of critters! Chaotic variability in river discharge (due to climate variations) can adversely affect migratory and resident salmonids at different stages of their life-history. However, in the relatively more stable chalk streams of southern England, drought and associated low river discharges (often exacerbated by human influences such as abstraction, flow regulation and land use), are thought to be the biggest threat. In the future, chalk streams are likely to suffer from periods of intense summer drought more frequently, with potentially disastrous implication for their fish populations.

We are studying three carrier streams of the River Itchen where complete control of the flow is achieved by altering sluice gates at the top of each stream. During the summer, the sluice gates will be lowered in order to experimentally induce low flow conditions. Each stream will experience a four week low flow treatment, reduced by 90%, 45%, or not altered (as a control). The following summer, the individual streams will be subject to a different flow treatment so that at the end of the three years, each stream will have experienced all the different flow treatments.

Samples of the riverflies and other invertebrates  will be collected from each stream throughout the year to enable any response in fish food to be identified, in terms of species composition and density. Salmonid stomachs will be flushed to determine their diet, and to enable the construction and assessment of food webs in each stream under each treatment. It is possible that reduced flow may result in the loss of certain habitat types that are required by some invertebrates (e.g. decreases in stoneflies may occur where fast flowing habitats are lost) which, in turn, will affect salmonid diet as they respond to the change in prey availability by becoming increasing reliant on alternative food sources. We may see a shift in stream food web dynamics under different low flow conditions.

The movement and behaviour of salmonids may also change in response to reduced food availability, with fish increasing their foraging range to seek out food of a better quality or more suitable instream habitat. However, salmonid movement may be restricted due to the reduced amount of available habitat during the low flow period which could cause and increase in foraging competition due to fish density increases. To help me tease all this apart, I will monitor behavioural responses using Passive Integrated Transponder (PIT) tags inserted into individual fish to monitor habitat choices of salmonids before, during and after flow reduction in all three streams.

Results from this three year project will increase our understanding of the impact of short term summer drought events, which is vital to safeguard salmonid populations in these streams and to define future catchment and water resource management strategies for the south of England.

If you have any questions or comments, I would love to hear from you, and I hope to reappear on these pages to update you as the project unfolds.

Jessica (j.picken@qmul.ac.uk, or @jesspicken)

Fishing and family holidays for 2017 in the WTT auction

Fishing and family holidays in 2017 in the WTT auction

Short, grey days and limited fishing opportunity over Christmas and New Year tends to make me think of summer holidays.  As I write the lot descriptions for the WTT’s annual fundraising auction,  especially the ‘fishing overseas’ section,  I can dream about travelling to exotic rivers to fish in warm sunshine.  This year, it occurred to me that many of the ‘overseas’ lots could be combined family holidays, and perhaps some advance notice might be useful to aid planning.

This blog post describes some of the lots in Europe and the UK that could easily be combined with a holiday with the family or non-fishing partner. Watch out for the next blog post with fishing holidays further afield: Iceland, the Bahamas, Argentina and Zimbabwe

The chalk streams of Normandy provide excellent trout fishing, and mix well with fine food and visits to historic towns and beaches. Check out lots on the famous and historic Fario Club beats on the Rouloir and Fario Club members' beats on the Andelle. Previous winners of these lots have enjoyed the hospitality and good company of Laurent Sainsot, an Anglophile trout fisherman and tremendous WTT supporter (below left).

Near the Cote D’Azur, Tony Mair will take you on a walk (more of scramble, but perfectly safe …) to the bottom of the Verdon Gorge to fish the clear blue river between towering cliffs. Tony lives locally and will collect you from Nice.  A stunning location and a good break from the beach (below right).










If cooler climes and mountains are more your idea of fun, you could include a day with Chris Hendriks fishing for trout and grayling in rivers large and small in the Tyrsil area of Norway.

Chris is a leading light in the European tenkara community but you may fish conventionally if you wish – all you need bring are your waders as he can supply the rest. There are some lovely comfortable cabins nearby. (below left).










For sun and mountains, you can’t beat the Spanish Pyrenees.  There is some fantastic trout fishing here, but you need to know where to go, and how to get access through the complexity of permits, licences and private roads. Ivan Tarin and his guiding team will look after you not just in terms of fishing, but share with you the local Spanish food, wine and culture. A week in the High Pyrenees in midsummer might also appeal to a non fishing partner who is well catered for if they enjoy walking, wildlife, history and the culture of this beautiful area.  

High Pyrenees     Pyrenees lodge









Within the UK, we have some new lots this year that would combine beautifully with a holiday.

Pembrokeshire has a stunning coastline and is rich in birdlife and wild flowers. It also has some very good fishing both in the sea for bass and pollock, and, course, sea trout. Generous supporter Tony Richards has a cottage in Newport and a family member on the committee of the Nevern Angling Association. Thanks to him, we can offer a week in his cottage and a week's fishing ticket for two anglers on this excellent (but little known) sea trout river.

Dinas head

The Hebrides has quiet, sandy beaches and turquoise seas that are the envy of many Caribbean tourist boards. The fishing is for salmon, sea trout and wee brownies in the hill lochs. This year, we can offer a week in a cottage on Loch Fincastle on the Borve Estate of South Harris, including fishing in the tidal loch for salmon and sea trout. The cottage is short drive from the famous Scarista and Luskentyre beaches. 

fincastle    south harris









Full details of all these lots will be on the website and in the catalogue in early February. If you are not yet a WTT member please contact Christina and she will send you a printed copy of the catalogue office@wildtrout.org or call on 02392 570985. 

If you would like more detail now, contact me on dashton@wildtrout.org


Mike Blackmore: moving house, getting sick and still getting projects delivered

As a follow on from Mike Blackmore’s ‘Mad March’ blog, this is what he has been up to recently, or rather this blog post is about the challenges of moving house, getting sick and still getting projects delivered!  
You can read more about some of the projects Mike has been delivering in our Autumn Newsletter

Mike is the WTT Conservation Officer for the South and West. 

Mike says:

Between the end of August and November I have 

  • ·         Spent 42 days in-river delivering habitat enhancement/restoration projects plus 17 days out doing some other kind of away from the office activity (site visits, meetings etc.)
  • ·         I’ve worked on 16 different projects in 10 rivers across 4 counties with 3 EA offices, 2 Wildlife Trusts and 2 Rivers Trusts.

My waders are all trashed, my chainsaw needs serious TLC, the van needs a good power wash and a service and I needSt James Leat a holiday. Unfortunately, all of these have had to wait because midway through the Dever project we moved out of our house and into temporary accommodation, putting everything into storage whilst we awaited exchange of contracts for our new property.

In an attempt to make things easier for ourselves, Lotte and I rented a self-catered cottage for the second week of the Dever project (to reduce stress levels and commute distance). Cue Noro virus, violent sickness, 48 hours without food or sleep and literally using a stick to hold myself up whilst directing the diggers on site. Didn’t reduce stress levels but I did shed a few pounds!


After the Dever project I attempted setting up a temporary office in my parents garden room only to discover that mobile reception and internet in their corner of Somerset is powered by druidic chanting, steam and wishful thinking.

Otter PVThe next attempt at an office was my parents in-law’s campervan which despite being parked on a steep driveway and containing a purely ornamental electric heater, did have power and 21st century telecommunications. However, late on a Thursday evening I was informed that the campervan was going away to make space for builders that were coming next week. Attempt 3 at an office space was at my sister’s house which during the day contains her sleeping nightshift-working husband and a small dog that, despite being very cute, enjoys tearing lumps out of my spaniel.


We’ve now finally arrived in our new house and I’ve got a chance to catch up on report writing and such. It’s just dawned on me that I have three months to get four projects up and running for March I’d better crack on. Maybe I’ll take that holiday in May!

An enthusiastic response from Yorkshire

You may have seen via the WTT news pages or via Twitter that we were awarded a grant from Yorkshire Water’s Biodiversity Enhancement Fund which is part of their Blueprint for Yorkshire.

According to Yorkshire Water: The Wild Trout Trust secured funding to deliver projects across multiple locations within the Yorkshire Water operating area. Projects focused on work to restore, improve and maintain becks, rivers and wetlands. This work is in line with the government’s Catchment Based Approach plans for river management and is in in partnership with the EA, the Rivers and Wildlife Trusts, and local community groups. The proposal also focused on enhancing volunteer’s practical skills in order to enable them to apply learnt techniques on other nearby sites and create a network of environmental stewardship groups for the future.  

This proposal was successful because the project benefits BAP species and habitats as well as focusing on mitigating the impact of YWS neighbouring assets. The emphasis of the project on upskilling local groups was also valued.

Obviously improving habitat is key to the aims of the WTT but our impact is all the greater because of engagement and collaboration with grass roots organisations, and these Yorkshire Water funded ‘habitat demo days’ were my first opportunity to lead workshops on my local patch.

After discussions with Don Vine at Yorkshire Wildlife Trust, Pete Turner at Environment Agency (of course), Craig Best at the National Trust, and Nick Chuck of Bingley Angling Club, I settled on two small tributaries of the Aire (Howgill & Granby becks) within the grounds of East Riddlesden Hall, opposite Marley Sewage Treatment Works. As a part of the agreement with Yorkshire Water, some of the funding will be used to create a semi-permanent wetland (planned by Yorkshire Wildlife trust) which will contribute to natural flood management via water storage. As an example of some of the leveraged funding achieved, the Environment Agency have funded the livestock exclusion fencing along Granby Beck which ensured that all our instream habitat works were protected and the benefits realised more quickly.

My reasons for choosing this site were numerous, but spawning habitat is relatively rare on the mainstem Aire and hence looking after the numerous but all too commonly abused small tributaries, the capillaries of the river network, is very important if we want self-sustaining, resilient wild trout populations. There is the added advantage that it is relatively easy to demonstrate various restorative intervention techniques on small tribs that are scalable, and then let volunteers get stuck in both literally and practically.

Sixteen people attended each of two consecutive Saturday workshops at East Riddlesden Hall. Participants came from a variety of sources but I was blown away by the fact that representatives from nine different angling clubs attended, including Appletreewick, Barden & Burnsall Angling Club, Skipton Angling Association, Bradford City Angling Association, and even as far afield as Knaresborough Anglers Club. There was also a volunteer team from ComputerShare but from the degree of energy and enthusiasm, you’d never have guessed that they were office/desk-bound for the majority of the week! They appeared genuinely proud of their achievements and new found skills. One of the most gratifying moments for me was overhearing two committee members from an angling club on another catchment, stood next to one of the pinch-point interventions, discussing exact locations where they could apply such a measure on one of their own waters. Bingo!

I created a social media summary via Storify, here. Some of the take home facts and figures from the two days at East Riddlesden, and a similar demo day run by colleague Gareth Pedley with Caitlin Pearson of Yorkshire Dales Rivers Trust on Skeeby Beck, are summarised in the infographic below.

Please contact me if you have ideas for similar workshops or practical visits that could be considered for support under our partnership with Yorkshire Water.

Diving in on the Dever

It is incredibly difficult to drag our Conservation Officer for the South & West, Mike Blackmore, out of the river (where we know he prefers to be). Therefore, in order not to distract him from his valuable work before the end of the ‘in-river’ season, we asked Kris Kent to update us on work to restore the River Dever. Kris has been fly fishing and trotting for brown trout and grayling for over 20 years in the UK, Europe and Scandinavia. He is PR Officer for the Grayling Society and helps WTT with our online communications and events. (WTT Director: he’s also a bloody good egg – thank you, Kris, for all your help).

I was between jobs so I emailed Shaun Leonard, Wild Trout Trust Director, to see if there was anything I could help out the Wild Trout Trust with.  I was thinking of a little light administration, spreadsheets, reports or the like.  Within a few minutes Shaun called me on the mobile.  “Did I fancy helping out Mike Blackmore with a project he was working on?”  I said “Why not.”  Shaun suggested I call Mike to make the necessary arrangements.  Mike seemed a little bewildered by the fact that I was going to be helping out but he suggested that I start the following Tuesday and filled me in on the logistics.

In Guildford on business and on my way back to home in Lambourn, I realised I would be passing close by the project site, so I popped by to make sure I knew where I would be going the following week.  I pulled off the narrow lane that skirted the river by the pretty little church of Saint Michael and All Angels. Mike’s white VW Transporter was parked up by the stables so I knew I must have been in the right place.

Mike Blackmore Wild Trout Trust river restoration conservation

Saint Michael and All Angels, and the team working hard

I decided to take a quick stroll along the river and see if I could find Mike and the team and see what was going on.  It didn’t take me long to find them.  Mike and Jonny, the Keeper, were being ably supported by volunteers from Sparsholt College.  They looked a little confused as I strode down the path in suit and brogues!

Mike walked me down the river explaining the background to the project, the problems being addressed and the plan for the project.  The Environment Agency had identified this reach of the Dever as being an ideal opportunity to undertake a major habitat restoration project with the Wild Trout Trust as part of the Test and Itchen Restoration Strategy. Following engagement and planning with the riparian owners and the team that run and maintain the fishery (Fishing Breaks), a project was pulled together.  The project was funded by the owners, the Environment Agency and a donation from a WTT partner, Springwise, through an initiative called 1% for the Planet by which environmentally-minded businesses can donate 1% of their turnover for work to improve our natural environment. Fishing Breaks also provided skilled labour in the form of River Keeper, Jonny Walker.

This section of the Dever was suffering from a number or problems.  Impoundments meant that long sections lacked significant flow and had led to siltation of the spawning gravels, uniformity of habitat, and tall, vertical banks.  It was overwide in many places and had been artificially straightened. The uniform habitat was limiting biodiversity and, whilst there was a reasonable head of wild trout and grayling, the lack of suitable spawning habitat was hindering recruitment and a lack of refuges meant that fish (particularly juveniles) were vulnerable to predation.

The project had two phases. Week one focused on opening up the canopy in strategic places to let more light in and aid weed and marginal plant growth.  The wood generated would then be used to create flow deflecting woody habitat features.  Woody mattresses and hinged bankside trees would create fish refuges and trap silt, providing additional marginal habitat. Together these would help narrow the channel, increase flow, scour gravels and create a more sinuous, meandering channel.

river restoration wild trout trust chalkstreamriver restoration chalkstream wild trout trust

Creating a woody mattress, and the plant required for 'dig and dump'

In week two, the heavy plant would arrive. This would enable the team to do some ‘dig and dump’.  Pools would be dug out with the waste materials from that process used to create marginal berms that pinch the channel and accelerate flow. Then, new gravels would be introduced to make the new pools more hospitable for fish and provide spawning opportunities at the tail of each pool. Additional riffles would also be created to further diversify habitat. Sections of tall, steep bank would be re-profiled to improve floodplain connectivity, improve marginal habitat and provide easier access for anglers.

So I arrived at the beginning of week two and found the river already transformed. My job was to run around and help out with anything that needed doing, freeing up the professionals to focus on the important stuff.  After the digger had introduced the gravels into the new pools, I would follow on and rake them over, blending them in and tidying them up.

I helped peg in some woody debris as juvenile refuge habitat and I stacked up the leftover wood and piled up the brash ready to burn.  During week one, the team had created a new river bank along an over-widened section. During week two, I helped to back fill this area and translocate marginal plants to the new bank edge.

river restoration chalkstream wild trout trustriver restoration wild trout trust

Creating new bank

By the end of the week, I was exhausted, not being used to such manual work.  But the sense of achievement was almost overwhelming. Seeing the transformation from degraded to vibrant habitat gave me a huge sense of satisfaction and pride. And the fish loved it too.  Minutes after digging a new pool, the fish had already moved in and in one small pool we counted over twenty trout and grayling. I can’t wait to go back in six months or a year and see how the river has settled into its new setting.  The other thing I enjoyed was the sense of camaraderie, working together on such an important restoration project. I highly recommend it.

river restoration partnership

A few of the team!



Easements on Eastburn

A number of my blog posts have featured Eastburn Beck. It’s my pet project because it is the first that I cut my teeth on after moving to Yorkshire, because I live overlooking its headwaters and hence it is a very easy and accessible site for me to monitor. It is also exciting because it has ably demonstrated the value of partnership working, and how with critical mass, relatively small habitat improvements are snowballing both up and downstream from the original work plans as word spreads; this is quite typical for projects that the WTT is involved with!

Eastbunr Beck weir mill river restorationEastbunr Beck mill weir river restoration notch

Pre & post some weir notching we undertook on Eastburn Beck at Lyndhurst Wood. The channel width is narrower with more natural pool, riffle, and depositional features

To date, the project has involved me (WTT), the Environment Agency (via the powerhouse that is Pete Turner), Yorkshire Wildlife Trust, Bradford Environmental Action Trust, the Woodland Trust, Aire Rivers Trust, and Green Port Hull, as well as some very cooperative local land / structure owners. It has attracted a reasonable amount of media coverage too: Craven Herald, Keighley News, a colour spread in the Yorkshire Post magazine, and in Fieldsports magazine (the latter two instigated by top WTT chum, Andrew Griffiths). It was even the feature of Pete Turner’s first ever blog!

So, I can’t say that I’ve seen it through to completion – when can we truly say that a river or stream has been completely rehabilitated to a pristine condition with the number and diversity of stressors acting upon them nowadays? It’s a job for life! However, I can say that the Beck is slowly returning to some version of the right track and hopefully you can follow its continuing evolution through these blogs. Check out the green tabs at the bottom of this post which will link you via key words (connectivity, weirs etc).

I’m currently working on a fish easement for the shallow concrete sill of a road bridge next to a former mill. More connectivity issues – see the recent news item for how often these crop up in WTT Conservation Officer workloads. This particular phase of work has been supported by funding from Green Port Hull, via a grant awarded to Aire Rivers Trust & WTT. There are several kilometres of becks and trickles with reasonable to good quality spawning habitat availability above this obstruction, so it is a likely bottleneck on the system limiting trout population potential. It is not classified as main river but one still has to apply for consent to install any structures which might affect flow and perceived flood risk; in this case, North Yorkshire County Council were very cooperative.

Prior to any installation however, the scientist in me was keen to assess just how much of an obstruction this particular weir and culvert combo was. Cue a call to those good folk at Ribble Rivers Trust and in particular Mike Forty (another name you might recognise from a past blog on making connections). Mike carefully set up a pair of telemetry loops at the lower and upper end of the culvert, and then together we spent a day electrofishing to capture trout from upstream. A total of 25 fish were tagged with Passive Integrated Transponders (PIT-tags) and released into the pool immediately downstream of the weir. The premise is that these fish that have been displaced will attempt to return to their ‘preferred’ location upstream; there is a scientific basis for this – see Mike’s report.

The headlines are that 40% (10/25) of the trout were recorded as attempting to jump the weir, and of those there was a passage efficiency of 40%; in other words 40% (4/10) of the trout that attempted to get up and over the weir and into the shallow water in the culvert did eventually make it upstream. I say eventually, it took those 4 fish an average of >10 minutes to negotiate the culvert. Interestingly, it wasn’t the larger fish that made it either, so perhaps the depth of water was insufficient for those larger fish. Despite some difficulties with the study, including a flash flood of epic proportions (2nd highest level ever recorded – typical), Mike and I are in agreement that the structure is a considerable obstruction to fish passage, let along geomorphology!

Now that passage (or lack thereof) has been assessed prior to any interventions, I can proceed with installing some oak baffles and a baulk to focus flows and increase the depth across the sill, whilst providing slack water refugia en route for fish to recover if required. Watch this space for future updates. 

Restoring longitudinal connectivity: a more holistic approach

Anyone who knows anything about fish in the UK will surely know Dr Martyn Lucas, the head of the Aquatic Animal Ecology Research Group within the School of Biological and Biomedical Sciences at Durham University. He’s an absolute legend and all round good bloke with whom I have done some research in the past. From amongst the many projects he is involved with, his group has published two papers this year revolving around fish passage issues. The first was led by Mike Forty (supported by the Catchment Restoration Fund, CRF) who wrote a layman’s version for us in Salmo and whom I have written about before on the WTT blog pages. Below is a quick summary by Martyn, reproduced with his permission, regarding the second output which included brown trout and bullhead as the study species.  

Jeroen Tummer’s paper concerns longitudinal connectivity restoration for stream fish communities, particularly in terms of the use of ‘nature-like’ passage solutions and obstacle removal, and the utility of a more holistic approach for evaluating outcomes. One of the key findings of our study is that quantitative fish surveys don't do a very good job in telling us whether connectivity restoration work for stream fishes has worked or not in the short term! There are much better ways of doing this as illustrated in the paper. However, they do provide valuable, contextual evidence about changes in the fish community towards or away from the restoration objectives, including those in the longer term (so long as standardised monitoring at a regular frequency is continued).

The study was part-funded by the Environment Agency's CRF scheme for the Deerness Connectivity Restoration Project run by Wear Rivers Trust in collaboration with several partners, including Durham University.

It is important that CRF has generated deeper "evidence" value, like the Tummers et al paper as well as widespread on-the-ground ecological improvements in support of Water Framework Directive improvements. During CRF programme planning, several key stakeholders argued for the importance of peer-review level evidence development as an integral part of CRF - I'm glad that advice was listened to by DEFRA-EA and I'm glad WRT and Durham Uni. have been part of that output.

Let's keep moving towards river connectivity solutions that support ecosystem processes, including dispersal of organisms, rather than those that concentrate on just a few species and life stages!

The paper abstract is available, here.

Food web responses to habitat rehabilitation

Connectivity is a recurrent theme of my blog posts. Last year I wrote about plans for notching some of the redundant low mill weirs on a tributary of the River Aire, local to me. Those plans will come to fruition in the next few weeks as Pete Turner (Environment Agency) and I have had our bespoke environmental permit consented to progress the works, so I’ll report back to show you how the channel is evolving. I also wrote about making connections and how Mike Forty’s PhD research with Ribble Rivers Trust had thrown up some really interesting results, especially regarding the importance of free movement for precocious parr; the published work is available here.

To communicate the worth of habitat restoration work (in supporting the Ecosystem Service approach & Natural Capital principles) to the wider public and to potential future funders, and thus maintain, increase and maximise the potential impact, there is an urgent need for some simple and accessible assessments that a broad audience can appreciate. I have proposed to use the concept of the food web in this context because: a) the knock-on effects of habitat degradation translate into food web alterations very quickly; and b) the food web is recognised by a broad swathe of society (and from a very early age). Hence, measures of food webs can be used as an engagement & educational tool that will increase the understanding and value of restoration projects, as well as a tangible and effective measure for funding applications.

Ribble Calder elctrofishing science weir barrier fish passage

Bluebell Wood Weir on the Calder, Towneley Hall, Burnely

Yesterday, I spent a day putting this idea into action on the Calder at Towneley Hall, Burnley, with Gareth Jones of the Ribble Rivers Trust and keen volunteer, Tim Eldridge. As part of the Heritage Lottery-funded Ribble Life Project (part of a catchment-based approach to river basin management to help deliver the Water Framework Directive), we will use stable isotope analyses to characterise the food webs of short river sections to see how they respond to a weir removal. These will be compared to food webs on reference sections to determine the change associated with the actual weir removal. The weir will be removed in early 2017, so we were taking basal resource, invertebrate (riverfly), and fish samples yesterday to assess the situation prior to any intervention.

volunteer electrofishing research brown trout parr

Weighing and measuring catch; and releasing a fine brown trout parr

It was encouraging to see some fine trout and eel specimens, as well as a reasonable diversity of invertebrates from a river which has been historically shunted to the side of the flood plain, shortened and steepened, fragmented by weirs, bordered with invasive plants, and formalised into a park in areas. Just imagine how good it could be with the barriers removed! 

Calder Towneley Hall Burnley Ribble

Reference section of the R Calder - not perfect, but better than above!

Coping with climate change

After the winter spates and ‘unprecedented’ flows rearranged much of the substrate of my local river, the Aire in N Yorkshire, there has been virtually no rain since. Consequently, it is already at late summer level, and the lack of energy has allowed thick scums of bacteria and other microbes to develop on the bed. The lethargy of some of the trout seems to reflect that of the river. And the forecast is for a hot summer, allegedly.

This leads me to my monthly scan of the literature for research involving brown trout, which has thrown up two recent papers assessing impacts of climate change via modelling. The first was a study of trout populations from two streams on the Iberian Peninsula, where trout are at the edge of their natural distribution. Ben Tyser reported for WTT on earlier work in this region – see the WTT Library (Articles by topic) page on Climate Change: Iberian trout threatened by climate change.

The purpose of the new study was to determine the realised thermal niche, the actual environmental temperature window at which the population was comfortable if you like, and then predict how climate change may affect their range distribution in those streams. The authors comprehensively assessed current trout abundance via electrofishing at 37 sites, and developed a robust relationship between air temperature and water temperature along the altitudinal gradient of the streams to relate to the trout distribution. Being able to convert from air to water temperature allows the authors to use the air temperature predictions available from the Intergovernmental Panel on Climate Change (IPCC) reports to predict the water temperatures that trout may experience in the future.

It appeared from the extensive dataset that water above 18 °C was not favoured by trout and this temperature limit is actually lower than the accepted physiological thermal range, ie trout should be able to function and grow ‘normally’ up to 20-23 °C. Hence, while physiology may dictate the limits of fish tolerance, these limits can be more constrained by additional restrictions, such as competition or hydromorphology, and hence the realised (actual) thermal niche was smaller than the fundamental (theoretical) niche.

Using the most unfavourable climate change scenario predicted by the IPCC, the trout habitat loss based purely upon water temperature change increased to 38% and 11% for the two streams in an upstream direction at the end of the century, 2100. Important then, as WTT so often advises, to maintain and protect riparian vegetation, especially trees to provide shade and keep the water cool alongside many other benefits.

The second paper uses a combined ecological and evolutionary approach to determine whether trout can adapt in time to keep up with climate change. The authors argue that to implement effective management and conservation measures, it is crucial to quantify the maximum rate of change that cold water, freshwater fish populations can withstand. They developed a model that incorporated aspects of river dynamics, the bioenergetics of trout, and adaptive habitat selection, and built in a novel component that allowed for genetic and life-history adaptations. Two key traits, trout size at emergence and the maturity size threshold, the authors proposed would be highly influential.

trout life cycle

A modeller's view of the trout life-cycle

To illustrate potential applications of the model, the authors analysed trout population shifts and evolutionary dynamics under scenarios of climate change-induced warming (ie similar to the first study reported above), and warming plus flow reduction resulting from climate and land use change. They compared the outcomes of their model to a baseline of no environmental change.

The model predicted severe declines in trout density and biomass under climate warming. The rates of decline were substantially greater under the combined warming and flow reduction scenario. Not good news; there was a distinct probability of population extinction over contemporary time frames. Therefore, the adaptive capability of trout (as modelled) could not prevent extinction under high rates of environmental change. We must hope that under real world scenarios, a few of our remarkable trout will have the variation in their genetic tool-box to cope when it comes to the crunch!

If you are interested in reading more (and in layman’s terms) on how trout adapt to warmer waters, it is worth returning to your latest edition of Salmo (May 2016) for the excellent article by Dr Eoin O’Gorman – Icelandic trout: adapting to life in warm water. As he pointed out, trout do show remarkable tolerance to warmer waters, but it is the lethal limit for development of trout embryos that may be critical and if fish cannot migrate to cooler waters to spawn then the population will suffer. Connectivity is key! Let’s hope the new research project he is involved with, Ring of Fire, sheds further light: follow @Arctic_Biology on Twitter for updates of that work.

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