juggalo wrote: 
 why does the department of fish and wildlife feel it necessary to kill off a lake just because certain fish are thriving.why do we care so much about trout which have to be raised in a hatchery in order to survive. EVOLUTION.I've seen studies where wild runs of salmon and steelhead have been decimated by the poor genetics of hatchery mates.fish like bass,catfish,bluegill,walleye,and perch taste better and pound for pound are more fun to catch.I'm not saying we should be irresponsible about manageing our fisheries,but what about the long term efects of poisoning our lakes.
can anyone explain to me who,why,when,and how they kill off these lakes/do they have discusions or hearings before they decide to kill thousands of fish?do the communities involved have any say?
 
A lot of what you say is your own personal preference such as to the taste of the fish and sport quality.  Hatcheries are used because of the sheer overfishing that is done.  If there was no hatchery plants the lakes would be wiped out.  A lake is killed off because there was introduction of invasive species that is over competing for the nutrient load of the lake.  Spiny rays take a lot longer to grow to decent sizes up here in our colder waters than they do down south.  If my memory serves me correctly only cutthroat trout was native to NE washington lakes, rainbows were introduced....I couldnt find the source again so I may be incorrect.  With that being said, all spiny rays (perch, bass, crappie, walleye, etc) were introduced, more likely illegally.  To me there is no sport in catching perch or bluegill considering I've had many times when I've seen them bite a bare hook or sinkers.  Spiny rays are also voracious eaters of small fry.....which is the size a lot of trout lakes are stocked with.
Artificial propogation w/hatchery raising has a higher success rate than natural propogation.  I forget how much of a return my grandfather told me he used to get but it was by far greater than what you would see in nature.  I believe it was in the 70% or better range.  My grandfather (Gordon 'Ting' Baker) used to run the colville fish hatchery until the mid to late 80's.  Unfortunately he passed away last october so Im unable to verify information with him.  I do know he told me that fished killed with 
Rotenone could be eaten safely even right after it was applied.  South American tribes would take the plant roots used to mat rotenon, smash em up, and put them in the water and then go pick up fish as they floated to the surface, which was how we came to discover rotenone. We an eat fish killed with it because the toxin is poory absorbed by the GI tract but it is greatly absorbed through the fish's gills.  To put it simply, Rotenone disrupts 
cellular respiration (by interupting the electron transport chain).  And as cavdad45 says, the chemical becomes inert after a few days.  The long term damage comes from killing off a a portion of the nutrient load (other fish) that also produce waste which is a nutrient to plants, algae, etc.  After the lakes are killed off, the following year they are usually stocked with broodstock, catchables, etc.  The WDFW calls the practice of killing off a lake as rehabilitating it.
What I would like to see the WDFW do, prior to killing off the lake, is to remove all all restrictions on the lake ie no catch limits, and then kill the lake off a the end of the season...which they may already practice this.  I do believe they usually announce which lakes will be killed off in advance.
Another thing I would like to see done is when the fish come to the top, collect them, and use them to feed the homeless...but Im sure some civil groups would have a hayday with that saying we are poisoning the homeless lol.
BTW, Im just going off what I know and have read online, I may be off on some things as Im not a biologist (but I did get an A in Biology 101 hehe).  I would have went to be a 
Ichthyologist but I didnt want to go through that many years of school, move that far to go to school, and also it had a poor career outlook as far as I was concerned.......