WTT Blog

'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....

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.

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)

Here at WTT, we're (no pun intended!) all for reconnecting fragmented systems: see recent news items from Tim Jacklin's work on letting the Dove flow, applications of Mike Blackmore's patented #weirbegone, or some of my recent work with Aire Rivers Trust as just a few examples. Europe wide, indeed globally, there is growing recognition of such issues but do we know even the true extent of the problem? Hence, it's great to hear from Siobhán Atkinson regarding her current PhD research.

River connectivity is vital for sustaining healthy freshwater ecosystems. It is important for maintaining resident as well as migratory fish populations, natural sediment movement, and habitat for macroinvertebrate communities and other aquatic organisms. Despite this, few rivers remain uninterrupted across Europe.

At the WTT Annual Get Together earlier this year, I had the pleasure of bumping into a former MSc student of mine, Simon Whitton, who now works at Affinity Water and is collaborating with colleagues at Cranfield University, supervising PhD students of his own; a perfect opportunity for another guest blog or four! Since abstraction and chalk streams have hit the headlines repeatedly and this year especially, we should follow Mickaël's progress with interest (and that of Jess Picken too)....

Chalk streams are highly important ecosystems and are a fundamental component of the landscape in the south and east of England. They are hotspots of ecological diversity and support important fisheries for trout and dace amongst others. However, the water that feeds chalk streams originates from groundwater, which is under increasing pressure from abstraction to supply our expanding urban populations. This conflict puts chalk streams squarely in the sights of environmental regulators and water companies as they try to find the best ways to preserve the ecology and the water supply. Hence, my project is sponsored by Affinity Water, and the Environment Agency, and is a part of Cranfield University’s Industrial Partnership PhD studentship programme.

As WTT Conservation Officers, we are asked to make assessments on what is good and bad habitat for trout populations based upon visual observation and expert judgement; this is the basis of a typical Advisory Visit Report. If we had the time and resource, we'd look to the fish themselves to tell us! In this latest blog from current researchers, Jess Fordyce from the University of Glasgow Scottish Centre for Ecology and the Natural Environment outlines how an understanding of the genetic diversity within a catchment can inform more efficient management strategies for safe-gaurding trout populations.

The brown trout, Salmo trutta, is an extremely diverse species in terms of behaviour, physiology, genetics and morphology. Brown trout can adopt a range of life-history strategies which include freshwater residency in rivers and/or lakes, or anadromy – the movement from fresh to saltwater and back again (ie sea trout). The diversity of brown trout in terms of genetics and morphology was the focus of my PhD which was funded by an EU project called IBIS (Integrated Aquatic Resource Management Between Ireland, Northern Ireland and Scotland) and the Atlantic Salmon Trust. My study site was the Foyle catchment which is a large dendritic (branching) system with an area of around 4500km2 located in both Ireland and Northern Ireland. This catchment is managed by the Loughs Agency. Like other catchments across Britain and Ireland, sea trout numbers have been sharply declining over the last few decades. Therefore, it is important to understand the genetic population structuring of brown trout (the pattern of genetic variation) and which environmental factors shape such structuring. From this information, it is possible to detect exactly which populations contribute significantly to the production of sea trout and hence provide focused management.

Just a couple of weeks ago, I posted the news article entitled ‘Where have the rivers gone?’

A typical British summer has since dropped a deluge of rain across much of the countryside, and with it, will wash away any thoughts of droughts and painfully low flows from most people’s minds. It’s exactly the same with flooding:-