by Peter Lapsley via FlyFishing & FlyTying
one of the more interesting articles i’ve read on this oft heated argue/debate: preserving the genetic and ecological integrity of wild indigenous trout species while introducing farmed diploid (fertile) or triploid (infertile) trout to their environment.
in the article we’ll notice that a few taken-as-facts notions aren’t what we might have thought.
even if these studies where performed in the UK let’s not forget that most ‘wild’ brown trout around the world where stocked, brought in from elsewhere, not exclusively, but often from the UK so these findings are probably valid for any trout waters around the globe, and since they’re salmonids we can also suppose that these findings could very well be applicable to all the other salmonids whether they be purely freshwater or seagoing .
ok, i’m no ichthyologist and that last part is just a guess but i’d bet its mostly true. anyhow,
here’s a few random tidbits from this great article i highly recommend reading in its entirety.
“It seems reasonable to suppose that farmed brown trout stocked into rivers will necessarily discomfort those rivers’ wild trout – that they will harass the wild fish, dislodging them from their lies; that they may prey on small wild fish, particularly if they themselves are large; that they may disturb wild trouts’ spawning redds; or worse, that they may mate with wild fish, diluting the genetic integrity of wild trout populations.”
“Intriguingly, the outcomes show the suppositions set out at the beginning of this article to be completely wrong on both upland and lowland rivers, chiefly because wild trout – far more stream-wise than farmed fish – have no difficulty in holding their own.
There was no statistically significant drop in abundance or growth of wild fish when stocking took place. Stocking did not cause the displacement of wild fish. Fish formed a very small part of the diets of both stocked and wild fish, and bullheads, stone loach and minnows were the predominant species found in the stomachs of the few trout that did occasionally take fish. The growth of stocked fish was negligible.”
“The question that must niggle away in the back of one’s mind, of course, is how so distinct a sub-species could have come to be present in waters as far apart as Lough Melvin in Ireland and Lochs Awe and Laggan in Scotland. The answer may lie in the fact the as recently as 15,000 years ago there were no fish at all in British or Irish lakes or rivers, because those waters were buried beneath 13,000ft of ice. All our freshwater fish came in from the sea after the ice cap had receded.”
and that’s just to wet your appetite. click the trout image for the complete article, enjoy !
Sonahgan trout image courtesy of Paul Vecsei on flickr