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River Colne Water Vole Translocation Project

River Colne Water Vole Translocation Project | Essex Rivers Hub
Date: 2007
Project Lead: Essex Wildlife Trust

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Project Partners: DP World, Colchester Borough Council, The Woodland Trust, private landowners
Funding: DP World

This is a partnership project between Essex Wildlife Trust and DP World, with the assistance of Colchester Borough Council, The Woodland Trust and numerous private landowners along the River Colne from Halstead to Colchester.

Surveys of the River Colne in 1998 revealed a decline in water voles which coincided with an increase in mink sightings. By 2004, no surviving water vole colonies could be located on the main channel with a small number of voles on a tributary near Earls Colne finally gone by 2006. In 2007 an Essex Water Vole Recovery Project was initiated by Essex Wildlife Trust but the River Colne was not included in this initial phase.

In 2009, a major port development on the Thames at Corringham threatened to displace several hundred water voles. In order to ensure these animals would not only be moved to safety, but could further the strategic aims of the Essex Water Vole Recovery Project, it was agreed to translocate them to the River Colne. The project, funded by DP World, involved 5 years of mink control and three years of water vole reintroductions. This is now the largest water vole translocation ever attempted in the Eastern Region with over 600 voles released between 2010-2012 along 6 miles of river from Halstead to Fordham.

Monitoring of the new water vole population has included radio tracking of 20 newly released voles, a dissertation thesis on water vole habitat suitability and recolonisation success and an undergraduate study on the effects of the 2012 flooding on water vole dispersal.

Secondary benefits of this successful catchment scale reintroduction have been the inclusion of water voles on three Higher Level Stewardship applications from local farmers who gave permission for releases on their land; the use of the river to train undergraduate and postgraduate university students in water vole ecology and radio tracking techniques; and improved breeding opportunities for kingfishers and nesting waterfowl from the removal of invasive mink.

Annual Riversearch surveys and nightwatch camera trapping of the river will continue to be organised by Essex Wildlife Trust throughout the catchment.

While funding for mink control ends in 2014 it is hoped that landowners, residents and parish councils along the Colne catchment will be willing to adopt monitoring rafts to maintain a safe environment not only for the water voles, but kingfishers, waterfowl and other wildlife along the river.

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The topics below represent the pressures that many waterbodies in the Combined Essex catchment face. They have been divided into six main categories, but it is quite often that these categories can overlap as pressures relate to each other.

Diffuse pollution occurs as water moves across the land or through the ground and picks pollutants. These pollutants can come from a variety of places, including urban and field run off. The pollutants that enter the river can range from sediment to toxins to excess nutrients, meaning that diffuse pollution can cause a whole range of different issues. The variety in these pressure groups means that it is something that can be quite difficult to tackle. It requires groups of people, business and stakeholders to work together in order to solve this problem.

Fish should be able to travel up and down a river freely, allowing them to move and breed in the most suitable habitats for them. It is important that fish populations do not become isolated, as this makes them more susceptible to disease and puts pressure on their survival. Unfortunately, there are often many barriers along rivers that prevent fish from being able to migrate up and down stream. Where barriers have been identified, they will be seen as a ‘pressure’ on a waterbody. Thankfully, there are many solutions now that can be put in place to aid fish passage, even over large barriers.

The flow in a river can vary greatly throughout the year as rainfall and run off can have an effect. This is a natural process. It is when flow is impacted by non-natural processes that it can cause problems. Sometimes, water can be intercepted or removed from a system; this will reduce the flow, therefore changing the habitat conditions. Some species are happy in high energy rivers. This means that when flow is reduced, these species will no longer survive. The opposite of this can occur when excess water is entering a river, for example through increased runoff. Low energy systems then become high energy and displace the species that live there.

A species that is not meant to be found in a particular area is known as an invasive species. Invasive species can be from a different habitat or a different country altogether. Most of the invasive species that we find on our rivers have come from other countries – plants that people have imported for their gardens or animals that have been released for food or by animal rights activists. Control of invasive species requires a lot of time and effort. We are fortunate that we do have a range of methods to manage most of the invasive species that cause havoc on our rivers, but there are still some which we are still struggling to control.

Many of our rivers have been heavily modified over the years as rivers have been used for a wide range of purposes. Physical modification is one of the biggest factors that causes our rivers to be unhealthy. The issues that it can cause range from reducing habitat, preventing migration of mobile species, and even have an effect on the water quality. Where structures and modifications are no longer in use or necessary, they should be removed to allow the river to regain its natural state. Unfortunately, this action is not always taken which means that many of our rivers are over straightened and contain redundant structures. It is possible to return a lot of our rivers to their natural state, through one off projects, but in other cases it is not possible as the river has been changed to protect assets or manage flooding. It is recognised that some modifications cannot be removed without having severe negative impacts both socially and economically.

This is pollution that comes from a single identifiable source. The pollution entering the river could include a whole range of pollutants. Some point source pollution is known about and licences, for example sewage treatment works. Other sources are not licensed, and therefore work needs to be done with landowners to fix the problems that are allowing the pollution to enter the river. Point source pollution is more easily controlled than diffuse pollution as it often only takes one management approach to solve the issue.