Cormorants and goosander have decimated the silver fish population of the Severn around Shrewsbury, there has been a massive decline in numbers over the last 10 years. It's not unusual to see groups of up to 40 goosander systematically working a stretch, they probably do more long-term damage than cormorants as they tend to take the juvenile fish. Fishing maggot on the river in summer used to be almost impossible due to the numbers of minnows and small silvers, these days you're lucky to get a bite!
Which is odd, because every time we have an 'Otter' thread, where people claim that otters have, or will, empty their waters of fish...we are told it is not possible. We are told that nature makes predator/prey relationships self limiting, that the numbers of predators rises and falls with the numbers of prey animals available. While this argument
sounds very convincing, it doesn't really explain the ever increasing number of cases recently where predators HAVE effectively emptied a water of fish, does it?
The number of rivers where the scenario Steve describes has come about due to the increased predation by cormorants, goosanders etc, and recently by mink and otters also, is absolutely staggering. The 'self limiting' theorists usually claim that it is not really the predators that are responsible, that pollution, over abstraction etc., etc., are to blame. While this may very well be true sometimes, at least to a certain extent, on some of of our rivers....it certainly doesn't explain the total 'wipe-outs' that have occurred on perfectly healthy, enclosed lakes or commercial waters. On these waters it can be proved that NO pollution of any sort was present, either before or after the event (and the abstraction point obviously does not apply) The fact is that predators moved in, were seen attacking/killing/eating the healthy fish stocks, untill eventually...the time scale being dependent on the size of the water and/or the numbers of predators present, it was eventually declared virtually devoid of fish....and THEN the predators moved on
It really doesn't require a Sherlock Holmes to work out that for some reason, the 'Nature is self limiting' thing no longer applies on our waters (or at least to individual waters)...if indeed it ever did. The old 'fox in a chicken run' story always did throw a certain amount of doubt onto the infallibility of that theory anyway
It goes without saying that pollution, and all the other man made ills that assault our waters, are the MAJOR cause of most of our problems. However, in my opinion, the predator factor has now become a critical additional factor. Whether or not mans actions has once again bought about this situation...and whether or not pollution etc., has made our fish stocks more vulnerable to the effects of predation....is a mute point. The point I am trying to make is that while the fight against the old enemies of pollution etc., must obviously carry on, the issue of what to do about the huge problem of increased predation should NOT be swept under the carpet, by denying it's very existence.
Cheers, Dave.
