Avon roach and the wisdom of restocking

Last July I wrote about my misgivings over the Avon Roach Project (ARP) on the grounds that there appeared little evidence to suggest roach stocks were shrinking, apart from anglers’ anecdotes, and no reference to monitoring during the restocking years. I can find no reference to the Project on the Environment Agency website.

Recently I discovered a set of fish survey data on the gov.uk website containing observations that date back to the 1970s. So I’ve sifted through to see what it tells us about roach stocks on the Hampshire Avon. Surveys on the river only began in 2001.  Counts can usually be taken as proportional to the population in the survey area. The sampling profile is highly variable, perhaps dependent on resources available at the time. In 2001 four sites on the main river were surveyed, but apparently only one in 2002 and 2003. This jumped to 26 in 2004 with a similar number in 2005, dropping back to four in 2006. Presumably the increased activity coincided with reports of poor roach catches from anglers that subsequently led to the ARP’s inception.

The graph below shows counts of roach averaged over the survey sites for that year.

avon roach

There is a zero or missing reading for roach in 2002 and 2003, though very few fish of any species show in the EA figures for those two years. Roach counts pick up significantly in subsequent years but vary quite considerably over the 19-year span of the EA surveys, as would be expected for fish populations. If these counts are representative of the wider population, it is very unlikely that the ARP restocking project made any substantial difference over its lifetime. Its fish-rearing activity did not begin until 2007. At least two years would be required before any success could be measured. Yet the graph suggests stocks declined from 2008, with an upswing in 2011, then another fall. If 2011 was from the ARP stocking, the improvement was short-lived.

Care has to be taken when interpreting survey data. Possibly the counts during the low-sampling years before 2004 under-represent the stocks. Fish are not evenly spread throughout a river and survey results may be unrepresentative for this reason. But this is less likely with the more thorough sampling from 2004. Unless the survey data are completely unreliable, we should place little faith or money in restocking to restore fish populations that will recover in their own time.

5 thoughts on “Avon roach and the wisdom of restocking”

  1. Back in about 2000 I managed to get hold of the published fish survey results for the Dorset Frome, Dorset Stour and Hants. Avon. I only have the 1997 Avon survey and I was mainly interested in the Stour survey as I was researching what became my first book on roach, Big Roach. Breeding roach on the Avon wasn’t new; Mike Trowbridge of Longford Estate was doing this back in the 80s and 90s and possibly his predecessor Tom Williams had started the idea.
    It’s clear from all the surveys that only a small portion of river is ever sampled, less than 5% at best and the sites are chosen for their access and suitability for sampling. The Avon is mentioned as being too big in its lower reaches to survey accurately so that a stretch is stopped off then surveyed along each bank not the whole river. Different species vary in their sampling suitability; dace tend to be in open water so they’re OK but roach tend to be in the weeds and many may be missed. This means, and it’s admitted as such, that the sample doesn’t give an accurate idea of roach populations. Furthermore, roach aren’t evenly distributed through a river like the Avon; some stretches have very few roach, never have had many roach and never will have many roach, whereas other places, known hotspots, have always been noted for roach and regardless of stocking continue to hold roach – in and around Fordingbridge is a good example of such a place. These major surveys of all species took place on a rolling 5 year basis so that in any one year only one major river is surveyed i.e. the Avon was survey in 97, the Stour in 98, the Frome in 99. On the in-between years it looks like maybe a couple of venues are surveyed if there is the time and resources to do so.
    Interestingly, the 1997 survey shows that the venue that much fuss has been made of recently, Upper Winkton, isn’t on the survey venue list so what the roach populations were like there historically is hard to decipher.
    From the research I did back in 2000 it was clear a whole raft of factors affected Avon roach populations, including but not confined to weedcurtting, cormorants, strong/weak year classes, balance of species, over-fishing, trout farms, illegal releases of rainbow trout, decline of carriers, sewages, pollution etc. Of these factors the biggest change by far has been the cessation of mechanised weed cutting in 2010 which has increased the volume of water in the river, especially in summer, increased water temperature. made the river more ‘roach friendly’ with more food and cover, possibly to the detriment of young salmon(?).
    As an additional note Salisbury DAC have stocked substantial number of young roach into their waters in and around the city.

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    1. Thank you for your interesting comment. Looking through other parts of the EA data, it is clear that the limited sampling cannot possibly represent whole rivers. What I think is useful are the countrywide trends revealed when the counts are averaged over many waters. For example, I have looked at the counts of trout throughout the country and found numbers are broadly stable, showing some cyclic changes as you would expect.

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