WTT Blog - Tagged with connectivity

A WTT advisory visit in 2016 on behalf of Birdsgrove Fly Fishing Club (BFFC) to the River Dove, Derbyshire, identified seven weirs along the 5km length of river fished by the club. The impoundment of water by these structures is detrimental to river habitat, fly and fish populations,especially from a fish passage persepctive, and natural sediment transport. The advisory visit report stimulated a debate within the club about what could be done to improve the fishery and it was decided to work towards the removal of the two weirs that had been built by the club in the past.

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

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

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

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

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

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:

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.

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!

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

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).

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.

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.

Man-made barriers, obstacles, call them what you will, are commonplace along our waterways as we have (typically) in the past tried to harness or control the flow of water for our own use. Some of these installations were incredibly insensitive to the local and more widely spread ecology and physical processes in rivers and streams, not just the fish that might want free passage both up and downstream at all life stages, and in all seasons.

I recently spent an afternoon with Mike Forty, a PhD student registered at Durham University, and based with the Ribble Rivers Trust. His work, using telemetry to assess the efficiency with which fish can pass obstacles, has been enlightening, and some of the statistics he can rattle off are mind-boggling. His work was featured in the presentation that Jack Spees (Director of RRT) gave at our recent WTT Gathering and captured on video here. For example, the low cost baffle system that was installed on a previously almost impassable weir on Swanside Beck (picture to right) can now be ascended in 23 seconds (according to one sea trout), and several resident brown trout have been up and down it numerous times!

Eastburn Beck is a tributary of the River Aire in Yorkshire. It is typical of a northern freestone stream / river that has had a chequered history with industrialisation, and as a consequence, it has lost some of its vitality to the constraints of walled banks and a host of weirs. The walls keep long sections straightened and have allowed housing to develop on what would have been a far more sinuous, meandering floodplain. The weirs interrupt the natural progression of pool-riffle sequences and have choked the supply of gravels downstream.

The result is a series of impounded shallow sections with uniform depth, flow, and substrate on the bed, and little in the way of cover within stream. While some of the overly wide, shallow sections with plenty of jutting stones creating small pockets of turbulence provide excellent habitat for juvenile trout (and is also favoured by the local pair of dippers), there is a distinct lack of spawning, fry and adult holding habitat.