WTT Blog - Tagged with science

'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 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)

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.

April was a quiet month for me as my academic commitments stole the lion’s share. But I can’t believe we are already at the end of May! May is probably my favourite month…. here in North Yorkshire, the ramsons and bluebells are in full swing and the beech buds burst to dapple them in shade and provide such a vibrant, fresh green for a week or so. And then there are mayflies of course but that’s another story.

There has been much ‘Twittering’ of late as various organisations across the UK are venturing into classrooms to engage with children via aquatic beasties, and particularly our totemic species - the brown trout.

WTT chums at the Clyde River Foundation (CRF) coordinate #Clydeintheclassroom. It’s a huge venture, working with some 90 classes to engage with >2000 kids this year alone. It’s also very much a hands-on project, using aspects of the trout life history to promote awareness of river ecology, to engage with nature, and to help young people across the River Clyde catchment develop a sense of pride in their local environment. Furthermore, it provides a great basis for outdoor learning and STEM education.

The UK landscape is a mosaic primarily of agriculture interspersed with woodland, grassland, urban enclaves and veined with river networks and wetlands. We should all realise by now that this pattern in the landscape has a marked effect on 'ecosystem goods and services', the natural benefits that the environment provides to us, and particularly those associated with freshwater. How we use (or abuse) the land, i.e. influence the landscape pattern, and the downstream consequences to water quality are a focus of the current consultation on diffuse pollution to which WTT has already responded (and I encourage you to do so too).    

A new study of an urbanising but predominantly agricultural landscape in the US draws upon data from 100 Wisconsin sub-watersheds and has important implications for managing and restoring landscapes to enhance surface water quality, groundwater quality, and groundwater supply. The study considered the landscape pattern in terms of composition (the type and amount of particular patches) and its configuration (the layout of those patches); and while both appear to have some bearing upon freshwater services, the composition had a stronger influence on water quality and supply.