| Subject: Re: Silurus glanis - Would I be crazy to kill it? |
Author:
Zanderman
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Date Posted: 20:17:19 10/22/03 Wed
In reply to:
Carol
's message, "Re: Silurus glanis - Would I be crazy to kill it?" on 19:14:27 10/14/03 Tue
Hi, having read with some interest your discussion on non-native fish a few points i would like to add. I fish for zander on the Fens, another non native species that have been accused of eating everything.
1) As far as I am aware, homo sapiens are the only higher species that exhaust their food resources. It doesnt make sense for a species to eat everything in site.
2) Your expert appears to be a fish farmer and therfore I guess his views are slightly bias. Farmers and commercial fisherman are always making statements regarding rabbits eating everything, seals eating all the fish, etc. And yes in a fish farming situation I guess wels would be a problem as fish farms aim to get maximum yield from a piece of water.
3) In my limited experience of catfish in this country, they do appear to scavange rather than predate. Admittedly most catfish in this country exist in carp waters where there is a proliferation of boilies to eat.
4) The wels catfish although cold blooded does have a true stomach and therefore digests its food more slowly than native predators. In the cool waters ok the uk, the wels is living at the bottom end of its temperature range and therefore eats a lot less food than if in Spain.
5) Catfish have been being accidently caught in british rivers for years. I know of three genuine captures in three different Norfolk rivers over the last 20 years. So catfish have been present in the broads for many years, but they are hardly thriving. Well acutally they could be because no one fishes for them. If they are thriving and eating everything, then why are populations of Roach, Bream, Rudd on the Broads increasing?
6) I spent this summer fishing a water that has a healthy population of catfish up to 50lbs (23kg), it is a shallow gravel pit of around 6 acres and is absolutely boiling with rudd, bream and perch. The biggest cat was first caught 15 years ago and has slowly grown. No evidence of catfish eating everything.
7) When zander were first stocked into the fens nearly 40 years ago, they were blamed for the wipeout of stocks of silver fish. The so called fishery Scientists at the then river authority failed to recognise that the same winter fishermen in the wash were catching tons of roach and bream bodies in their nets. The silver fish were washed out through the sluices because of prolonged run off. Zander were the perfect scape goat. That story is responsible the the death of hundreds of zander every year by ill informed fishermen.
8) Whilst I agree that controls should be in place to monitor the spread of non native fish, I believe that our fisheries are under far more threat from abstraction, pollution and access issues than the catfish could ever could.
I would suggest that you contact the Catfish Conservation Group, and Norfolk Anglers Conservation Association, for some more details and possibly access to scientific papers. However scientific papers rarely provide an accurate picture of what is going on. I have found that taken collectively the information supplied by anglers to be far more of an accurate representation of what is happening with our fisheries. In case you were wondering, I have studied Aquaculture at University Level and am a qualified laboratory chemist.
Good luck with your research, but take a look at abstraction issue's they are far more dangerous than catfish.
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