Why should "Perch should be killed outright of course". They are just another predator fish like bass and trout and have just as much right to be another fish species in our BC waters.
Terry, both bass and yellow perch are invasive species and do considerable amount of damage to native fish (not just salmonids, in fact most damages are not conspicuous) in British Columbia. In sportfisheries, fish that are being illegally introduced take a big chunk of our license money. Yellow perch are particularly worse than other non-native species due to their ability to breed rapidly. Lakes that have been introduced with yellow perch have seen a complete wipeout of trout in Interior BC. Once that stage is completed, their population continue to explode due to a lack of predation and fishing pressure (although good table fare, the amount of harvest is dwarfed by recruitment). The population eventually reaches carrying capacity and all perch become stunted (similar to what Sam has said about the smallmouth bass in St Mary Lake). Once this stage is reached, the lake can pretty much be considered useless for anglers as the fish are too small for anglers to be interested in eating them.
Biologically speaking, non-native species are not just bad for existing sportfisheries, but lethal for non-sport native fish species. Beside perch and bass, uneducated individuals constantly dump unwanted aquarium fish species into our watershed. These species may not affect our sportfish, but they do tremendous amount of damage to other native species that we are not aware of by predation, competiton of space and food and habitat degradation.
Quite often when the issue of invasive species is brought up, there is a misconsumption that BC anglers are simply against bass and other freshwater spiny ray species. This is entirely false. As an angler, I enjoy fishing for all fish species. I enjoy my annual trip to St Mary Lake where an existing smallmouth bass fishery is available. Other than that, I believe that people should be travelling to where the fish are, not bringing fish to where they are. We live in a province where the ecosystems are only tampered slightly compared to the rest of the world and it should be our obligation to protect.
The Ministry of Environment and the Freshwater Fisheries Society of BC have expanded their effort on tackling invasive species. Unfortunately, they are currently at the losing end and will probably continue to be unless more support is generated from the public. Some of the projects that have taken place this year include closures of several lakes and poisoning of these lakes to start all over again. There are rewards (up to $10,000 I believe) being offered by the Ministry of Environment and BC Wildlife Federation for catching individuals who are illegally introducing fish into a new watershed.
More information on this issue:
http://www.gofishbc.com/alienspecies/default.htmhttp://www.env.gov.bc.ca/fw/fish/sport_fish/exotic/#Perchhttp://www.env.gov.bc.ca/wld/aliensp/alien_consequence.html