Measuring progress on the Horsbere Brook

Our fishery folk have been out on the Horsebere Brook in Gloucester undertaking an electro-fishing survey as part of our Fisheries and Biodiversity investigation programme. This was following work at Brockworth, between Mill Lane and the A46, to help address some of the issues that affect habitat quality and wildlife in the brook.

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The project manager, Cathy Beeching also invited members of the community and three Brook Wardens were able to attend.

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The brook is classified as poor overall for fish, under the Water Framework Directive, due to a lack of some fish species you’d expect to find such as bullhead and brown trout. This is partly because the shape of the river, and its banks, has been changed from their natural state over the years. Channel straightening, man-made banks, tipped rubbish and rubble have all reduced space for water and wildlife. Although the Horsebere Brook is a naturally active and changing watercourse, erosion and siltation has been exacerbated by water running quickly off neighbouring hard urban areas.

At the three survey locations, some eels, perch and roach fry were caught.

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Even two brown trout were found upstream of the habitat restoration site, showing a welcome improvement in fish species.

What were the Improvement Works?

As part of the Environment Agency led improvement works last summer we restored two cut off meanders. This lengthened the brook and created more habitat. One meander bypassed a section of concrete channel, which had scoured out a deep drop in the river bed and blocked fish movement.

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We also worked with Severn Trent Water to replace two failed and unsightly Storm Water Outfalls. The headwalls, which form the pipe outlet, were set a little further back from the bank, and constructed with more natural materials, to help them blend into the environment and reduce the speed of water entering the brook. At the same time the opportunity was taken to scoop out the river bank to restore a natural profile and wetland edge, and improve views and access to the brook, including more space for water in high flows.

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These interventions complemented an ongoing programme of improvements by the local community, with the Parish Council and Severn Vale Housing and Tewkesbury Borough Council, to stop fly tipping, and enhance the brook.

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We hope that all the volunteers who have planted trees, picked litter, maintained paths and made brushwood bundles for the restoration works will welcome the improving diversity of wildlife in this important urban brook.

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Chasing fish in the middle Severn

Last week, as part of a major survey of coarse fish in the mid Severn (from Shrewsbury to Worcester), we used a special piece of monitoring kit we borrowed from our friends in the South East region of the Environment Agency.

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It’s called an electrofishing boom boat and has been specifically designed to sample larger rivers. Catching fish in a big river presents lots of problems. It’s too deep and wide to net effectively, too big and deep for normal hand held electrofishing gear, and debris, obstructions and depth changes make sonar equipment unreliable. The boom boat is effective as it greatly increases the effective size of the electric capture field. The two large multiple rings arrangements on the front of the boat with metal prongs dipping into the water are the anodes and electricity passes between them and the cathodes (metal plates situated under the boat). This electric field then attracts fish towards the anodes and then immobilises them. The fish are caught by two people with nets on either side of the boat, and placed into an aerated storage tank on board the boat.

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Last week we fished between the County Showground and English Bridge in Shrewsbury. At various locations along this section fish caught were unloaded to colleagues on the bank.

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The team on the bank identify and count the fish, measure their tail fork length and take samples of scales which are sent for analysis. This tells us how old the fish are and how quickly they are growing. They are then released back into the water.

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We caught good numbers and a wide selection of fish including some large pike and perch, a shoal of roach, dace, chub, ruffe, gudgeon, European eel and juvenile Atlantic salmon as well as plenty of bullheads and minnows. A large adult Atlantic salmon was also seen but not caught.

The results from this investigation will be combined with match catch data from anglers and fry surveys to get a better appreciation of the fish population of this important fishery. We hope to produce a report on our findings later this year.

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Dead fish in the Droitwich Canal

Over the last week we’ve had a number of reports of dead fish in the Droitwich canal around Vines Park.

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We have visited on a number of occasions and have found a total of about 30 fish in varying states of decomposition. Every time we’ve been out oxygen levels in the water have been good and there’s no apparent pollutant present.

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All the fish we’ve found so far have been mature bream and our fishery officers are confident that they’re victims of spawning stress. Spawning requires a lot of energy, both through egg production and through chasing potential mates. Fish can get scrapes and lose scales when thrashing against sunken tree roots, rocks and each other. These wounds give bacteria a point of entry. Secondary infections can overtake and eventually kill weakened fish. While signs of bacterial infections can vary, many fish will develop open sores, ulcers with white coloured fungus.

While it’s a shame to see dead fish this is an entirely natural phenomenon and hopefully the results of the spawning frenzy will more than compensate for the losses!

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We have taken additional water samples from the canal to make sure that there really is no pollution and we will continue to monitor the area.

If you see any dead fish or fish in distress please call our incident reporting line on 0800 80 70 60. All reports we received are passed on to our local officers.

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Giving fish a helping hand on the River Isbourne

The River Isbourne is a tributary of the River Avon. Only thirteen miles long, it rises on the Cotswold escarpment, joining the Avon at Evesham. It’s reputed to be one of only two rivers in the world that flows entirely south to north (the other being the Nile)!

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Our monitoring of the Isbourne has revealed that the river fails to meet the requirements for good ecological status under the Water Framework Directive. A major reason is the absence of some fish species we’d expect to find in a river of this type. Roach, Chub, Stone Loach and Minnows are missing from the upstream sections, while Roach, Stone Loach and Gudgeon are missing from the downstream part.

The problem

Like many English lowland rivers, the Isbourne has a number of redundant mills along its length, many of which have weirs and water management structures associated with them. These often represent significant obstacles to fish trying to swim upstream to breed or colonise upper parts of the catchment.

Because of its proximity to the Avon, the Isbourne should provide important extra habitat for fish normally resident in the Avon, as well as supporting its own resident populations. This means that barriers at the downstream end of the river have a disproportionately large impact.

Hampton Mill Weir

The first upstream obstruction on the Isbourne is at Hampton Mill, approximately 750m above the confluence with the river Avon. The legacy of a redundant mill, the two metre high weir was causing a moderate barrier to fish as the water flow was too fast and shallow to allow them to swim over it. During high flows and flood conditions the weir is drowned out allowing fish passage, but not during normal flow conditions. The picture below shows the weir before we got to work.

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Ideally we would like to remove barriers like these completely and return the river profile to its original state. This, however, is very expensive and can also sometimes lead to knock-on impacts to local flood risk and erosion.

A baffling solution

In the case of Hampton Mill weir we’ve attached a series of baffles to the existing structure, as seen in the picture below. The baffles, which are made out of recycled plastic, can be fitted quite quickly and don’t require any major structural work to the weir.

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The design is intended to increase water depth over the weir, and reduce the flow velocity. This will make it easier for fish to swim over the weir to reach additional upstream habitat, including spawning gravels.

We have also installed eel tiles along the right wall of the weir. Again, fabricated from recycled plastic they are covered with lumps and bumps of various sizes and encourage eels and elvers up the weir. They like to stick to the sides of things as they move along!

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The photo below shows water going over the weir after the baffles were installed last week. You can see that the flow is being significantly disrupted and the water velocity is reduced. This will make is much easier for fish of all species to pass. We hope that they will form an orderly queue to explore this lovely catchment.

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Our river monitoring programme will show how successful we’ve been over coming years.

Part of a bigger plan

Hampton Mill on the River Isbourne is just one of over five thousand structures across the Midlands that we believe is having and adverse affect on fish movements. Over the last couple of years we have been working to identify and rank them according to the impact that they’re having. This is part of our ongoing work to secure compliance with the Water Framework Directive.

We have a programme of projects across the region which address some of these barriers. We currrently have about a hundred different schemes being designed or built. Clearly there is a long way to go but by identifying and prioritising we can ensure what resources are available are used to best effect.