WTT Blog Posts

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)

Should I stay or should I go?

'Can I migrate?' is a question that we at WTT often raise on behalf of fish. In most instances, this question is associated with two physical factors. One is whether there is sufficient water in the river for fish to move through; a problem exacerbated in the southern parts of the UK by abstraction pressures. The other is whether there are any barriers or obstacles to free fish passage - and there are usually plenty! But 'Should I migrate or not?'  is an interesting one that does not get asked very often. Luckily I know someone who does ask such questions! With great pleasure, I hand over to Kim Birnie-Gauvin from the National Institute for Aquatic Resources at the Technical University of Denmark who is conducting her PhD research within the AMBER project.

Physiology & partial migration: from the free radical theory of ageing to residancy and migration in brown trout....

As many of you probably already know, brown trout (Salmo trutta) is a partially migrant species. This means that within a single population, some individuals will migrate to sea and become ‘sea trout’ while others will stay put and become ‘residents’. Many hypotheses have been formulated in an attempt to explain the evolution of such patterns, but today we still have a poor understanding of the mechanisms at play in choosing residency or migration.

Figure 1. Adult resident (A) and migrant (B) brown trout, Salmo trutta capture in a Danish stream (Images by Kim Birnie-Gauvin).

As an animal physiologist by training who has joined the field of fish ecology in recent years, my interests lay in understanding the physiological mechanisms that lead to ecological patterns as well as how fish cope in a human-dominated world. Currently, I am investigating the physiology that underlies residency and migration choices in brown trout. What makes an individual decide to stay in a river its whole life? What makes a seemingly identical individual decide to migrate to marine environments?

With growing evidence suggesting that oxidative stress processes were linked to life-history strategies, I investigated the role of these processes in brown trout partial migration. If you are not familiar with the term, oxidative stress is essentially what makes you wrinkle (also termed the free radical theory of aging) – it is a slow process which takes place when pro-oxidants (‘bad stuff’) are present in greater amounts than antioxidants (‘good stuff’), and damages your proteins, lipids and DNA. You might be wondering how wrinkling might have anything to do with migration… It’s a little more complicated than that, but it essentially has to do with how well a fish can cope with the demands of migration. Hence, you would expect that fish with higher antioxidants have a greater capacity to cope with migration, and may therefore migrate. Similarly, a fish with a lesser ability to cope with the demands of migration (i.e. lower antioxidant) may stay and assume residency.

This is exactly what my study showed.  Here’s what I did: I captured over 500 juvenile brown trout, obtained a blood sample from each of them and tagged them using PIT tags (passive integrated transponder tags). These are small tags that allow us to identify each individual with a unique identification. I then used the red blood cells to evaluate antioxidant capacity (which essentially requires a lot of time in a lab). 

Figure 2. Study design: electrofishing (A), 23mm PIT tag (B) and blood sampling (C) (Images by Kim Birnie-Gauvin).

The analysis showed the migrants had a higher antioxidant capacity, and perhaps enhance these antioxidants as part of the smoltification process in preparation for migration. We also found that within migrant individuals, fish that migrated earlier had higher antioxidants than those that migrated later – this may reflect a fish’s readiness to migrate. Do brown trout plan ahead?

Figure 3. Antioxidant capacity in resident and migrant brown trout (Salmo trutta).

So far, this has been the first evidence suggesting a link between oxidative stress processes and partial migration, not only in fish but in all animals. Though this is only the first step, my team and I are excited for what will come of this.

If you have any questions, please don’t hesitate to contact me by email at kbir@aqua.dtu.dk

Kim (@kbg_conserv)

Woodplumpton Brook Restoration: Baffle-ing Results!

With my ‘Research’ & Conservation Officer cap on, I can straddle the often hefty divide between academia and NGO/grass roots conservation groups and do a little bit to pull them together. Queen Mary University of London buy out some of my time and expertise from WTT to give their aquatic ecology MSc students practical training and experience in the field. As a part of a week-long fieldcourse based in the Lake District, I have forged a link between them and Wyre Rivers Trust but I’ll let some of the excellent members of this year’s cohort tell you about it, below. Thanks to Dr Christophe Eizaguirre and the rest of the students who worked efficiently on the day to provide the data, and of course, to Tom Myerscough from Wyre RT for sorting out the relevant permissions.

The Wyre is one of the key rivers of Lancashire, with its catchment covering much of the North of the county. It has historically been known as one of the best sea-trout fisheries in England. However, in the post-war 20th Century, like most rivers it suffered from intensified agriculture, urbanisation and new engineering methods, and these changes have cumulatively affected fish communities.

Brown trout, a fish which requires a diverse range of habitats to complete its lifecycle (loose gravel in which to lay its eggs, instream and overhanging vegetation to hide its fry, deeper pockets to hold larger adults) has been notably impacted. The Wild Trout Trust labels the brown trout as a sentinel species; its requirements mean that healthy trout populations are indicative of a healthy ecosystem (from the freshwater invertebrates to riverbank birds) so if it isn’t there, then something is likely to be wrong!

A river is only as good as its catchment, and starting small can make the task of river restoration less daunting. Hence, Woodplumpton Brook has been chosen as one of the Wyre River Trust’s target sites for improvement. Aerial photographs reveal how this stream has been straightened and channelised since the 1940s, processes which greatly reduce the diversity of habitats needed for fish to survive. No trout have been seen here for 20 years.

One issue, in particular, is that of artificial barriers to fish movement. On Woodplumpton Brook, a road-bridge culvert speeds up the water as it glides over a concrete slab. Under normal flow conditions, this creates a very shallow and uniform area of fast water for 15m which hinders the free movement of fish upstream, especially larger individuals. Structures like this impair other restoration efforts upstream, such as fencing off livestock, addition of woody debris and planting of willow, by preventing recolonisation by larger fish. Even seemingly small obstructions like this can have a large effect (e.g. Jeroen Tummers WTT blog).

A restoration intervention was put in place last year to reduce these connectivity issues. Baffles, large pieces of wood anchored to the concrete, were fitted in the culvert. They slow the flow by increasing sinuosity and creating slack water refuges, and increase the water depth, allowing fish to make their way from baffle to baffle and hence upstream.  

Several cohorts of Freshwater and Marine Ecology Masters students from Queen Mary University of London have conducted sampling to assess the impact on the fish communities both before and after baffle installation. Our data will contribute to the long term monitoring of changes at this site as a result of this installation and other restoration techniques that have been put in place over recent years. We got to learn and practice new techniques and at the same time contribute useful data for Wyre Rivers Trust; a win-win situation!

To determine whether the baffles are actually helping, electrofishing was carried out both upstream and downstream of the culvert. To gain a representative population estimate, 50m stretches containing similar habitat features were cordoned off using stop nets, and 3-run depletion sampling was conducted in each section.  Each fish was identified and its length carefully recorded. After each run, the caught fish were released outside of the survey area to prevent recounts of the same individuals.

Last year, i.e. prior to the baffle installation, the group surveying the fish community in the Brook found that the communities downstream and upstream were significantly different (Fig. 1), and that the average fish size upstream was significantly smaller than downstream (Fig. 2). This implies that bigger fish were discriminated against, i.e. that they struggled to swim upstream through the culvert.

Fig 1: Stacked bar chart showing the proportions of each species to the fish community at sites either side of the baffles per year. The 2017 sites (after restoration) are much more like each other than the 2016 sites (before restoration), suggesting that the baffles are doing their job, improving fish passage through the culvert.

This year, however, we discovered that the fish communities were more similar upstream and downstream (Fig. 1). In addition, the fish were of similar size downstream and upstream (Fig. 2). Together, this indicates that the fish can move more freely up and down the Brook.

Fig 2: Average fish length (± Standard Error), up (blue) and downstream (red) per year. In 2016 (before restoration), larger fish were typically downstream of the culvert, but in 2017 (after restoration) we found the opposite: the baffles have allowed big fish to migrate upstream of the culvert.

Additionally, the overall community was quite different from last year. One of the most exciting discoveries was that we recorded a brown trout – the first in Woodplumpton for twenty years, and perhaps a sign of the overall recovery of the Brook. However, chub and dace were found in abundance last year, whereas this year there were very few. Furthermore, this year stickleback and stone loach were most abundant, whereas last year they were not present or found in very low numbers. These differences, in conjunction with us collecting several recently dead chub specimens (including larger individuals in the upstream section), suggest that although the restoration works are improving connectivity and habitats within the Brook, pollution events undermining the work and altering the community structure.

The first brown trout for 20 years!

Thus, despite apparent success of the baffles in mixing fish populations, it appears that overarching factors are impairing the true restoration impact and that Wyre Rivers Trust still have some work to do with local landowners. It should be noted that this is only the first year of data collection after installation of the baffles, and it will be interesting to see what future cohorts of our MSc will find in subsequent years.

Liam Nash, Abbie Nye, Thomas Del Santo O'Neill, Pascaline Francelle & Alice Goodwin

If you have any questions re our report or the work of the Wyre RT on Woodplumpton Brook, please contact Dr Christophe Eizaguirre or Tom Myerscough, respectively.

Where in the sea are sea trout?

As anglers, we often struggle to find fish in a stream, river or lake / loch, and we're generally seeking the bigger fish! Keeping track of the vulnerable juvenile life-stages is even more tricky, and then imagine translocating that problem to the sea.... OK, so with advances in acoustic telemetry, the boffins have a few tricks up their sleeves and are making some headway but the logistics of tracking in such a potentially vast environment are nonetheless challenging. Isabel Moore from the Scottish Centre for Ecology & The Natural Enviornment has risen to that challenge during her PhD and outlines one aspect below.

The brown trout is a remarkably diverse species; it can utilise multiple life-history strategies, ranging from freshwater residency through to migration into marine environments for a period of time before returning to freshwater to reproduce (i.e. anadromous sea trout). Unfortunately, this iconic species has been faced with significant population declines in recent decades across the UK and other parts of the world. A significant portion of the anadromous population decline is thought to occur in marine environments. However, the sheer areal extent of habitats utilised by sea trout makes the monitoring of their movements very difficult, leaving many unanswered questions about the types of challenges that sea trout face and how those challenges might affect the their survival rates. Both environmental (i.e. predation, climate change, etc.) and anthropogenic influences (i.e. overfishing, aquaculture, etc.) have been identified as potential sources of increased mortality, but further research is required to determine the effect of each on wild sea trout.

Resident brown trout (left) and anadromous sea trout with acoustic tag on the rule below (right)

High mortality is thought to occur during the initial marine phase of the smolt life stage. However, we actually know relatively little of their whereabouts during this period. Recent advances in acoustic telemetry equipment have created opportunities to observe the movement of sea trout in marine environments. Such studies have been conducted in Norway and have found several interesting trends, such as preference of young smolts to stay in coastal areas near to their natal streams, and the impacts of high salmon lice loads on the behaviour of sea trout (i.e. early returns of sea trout to freshwater in order to “de-louse” themselves).

One aspect of my PhD at the University of Glasgow is focused on the spatial movements and habitat use of young sea trout smolts as they first leave their natal rivers, and what level of interaction they might have with anthropogenic structures such as fish farm facilities. An acoustic telemetry project at this level of fine-scale movement of sea trout smolts has not been carried out in Scotland before and it is hoped that it will shed some light on the current problems facing our local wild fish.

For this project, we chose two adjacent sea lochs on the Isle of Skye in Scotland: Loch Snizort and Loch Greshornish. An active fish farm facility is located within Loch Greshornish. In April 2017, in time with the natural smolt run, 30 sea trout smolts were captured from rivers in both sea loch systems using a combination of fyke netting and electrofishing.

Fyke netting for smolts in the R Snizort (left) and some of the hardware to anchor my telemtry receivers into the lochs (right)

All 60 smolts were anesthetised then tagged with a small acoustic tag that was surgically implanted, before being released back into the site they were captured from. Each tag emits a unique acoustic “ping” that can be “heard” by an acoustic receiver up to ~200m away. These data can then be used to identify when and where a specific smolt was located during the course of the study. The information is stored in the receiver until it is downloaded onto a computer.

Locations of the acoustic telemetry receivers in Loch Greshornish (left) and Loch Snizort (right)

A total of 40 acoustic telemetry receivers were split between the two sea lochs and placed in strategic lines across the lochs. Several “double curtain” receiver arrays were also used to gather information about swimming speed and directionality.

The limiting factor to my study is the battery life of the tags put into the smolts. Unfortunately they only last for ~80 days, so the length of the study was constrained from the end of April until the end of July.

Although the data have not been fully analysed yet, an initial glimpse has identified at least one fish that was successfully recorded moving between the two monitored sea lochs, and several fish that were identified near the fish farm facility in Loch Greshornish. Once the data analysis has been completed, a paper will be published with the final results.

If you have any questions, please feel free to contact me directly.

Isabel Moore (i.moore.2@research.gla.ac.uk or @izzy_moore89)

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