The Canaries of our rivers in Greater Manchester

Many of us have wonderful childhood memories of dipping nets into rivers and streams and marvelling at the different forms of life that we caught.  Who would guess that we have a group of volunteers doing the same thing in Greater Manchester, thereby creating a scientifically robust water quality data set?

Much like plants preferring different types of soil, the various species of aquatic invertebrates need certain environmental conditions in which to thrive.  They range from requiring very clean water, to others that are untypically tolerant to poor water quality and become very numerous due to the lack of competition for food.

We are very fortunate in our region to have a ‘hub’ of volunteers taking part in the Anglers’ Riverfly Monitoring Initiative.  They are trained and co-ordinated by Mike Duddy and Dr Adam Moolna of the Salford Friendly Anglers.  More information is available here. 

The survey involves taking a timed kick sample – essentially disturbing the streambed and vegetation to dislodge the invertebrates into a pond net.  The timed element helps make the results more comparable.  The catch is rapidly assessed before being returned to the waterbody.  A water quality score is calculated based upon the abundance of a carefully chosen and weighted set of families of invertebrate.

Identifying to species level is difficult, but as a family, they are quite easily recognised, and the member species all have the same general habitat requirements.  The families are predominantly larvae from a group known as riverflies such as caddisfly, mayfly, and stonefly; hence the name of the monitoring initiative.  An unusually low score, e.g. lots of specimens of a pollution tolerant family and/or few clean water invertebrates, could indicate a new problem that the appropriate authorities may be able to investigate.

Professional water chemistry testing by utilising sophisticated equipment and/or taking water samples to labs can produce more detailed results.  However, this high degree of accuracy is only necessary once a potential problem has been spotted.  Also, limited resources mean that this type of analysis can only happen very occasionally at few locations, whereas riverfly monitoring typically occurs monthly and has become widespread across the country.  What’s more, the invertebrate population is influenced by the water quality over a number of years; on the other hand, water testing is typically measuring a point in time and may well miss intermittent changes in the water.

The Anglers’ Riverfly Monitoring Initiative is a nationwide survey that was launched in 2007 by the Riverfly Partnership is a dynamic network of organisations, representing anglers, conservationists, entomologists, scientists, water course managers and relevant authorities, working together to: protect the water quality of our rivers; further the understanding of riverfly populations; and actively conserve riverfly habitats.

Natural Course is working with the Salford Friendly Anglers to make the results of their survey more widely available so that more organisations can use these pollution indicators in their river management plans.  We are also supporting and expanding their team of surveyors – such as funding training courses for new surveyors, and arranging an advanced identification workshop for their existing volunteers.

 Article and photos supplied by Mike Beard, Natural Course Project Officer at GM Local Record Centre.