I'm afraid you see the field of biology through rose-colored glasses.
Fisheries biologists in the past have often felt it was a good idea to introduce exotic species; in fact, this mindset is still pretty widespread among many agencies. Wildlife biologists were involved in the introduction of grass carp to the midwest, peacock bass to Florida, Nile perch to the Rift Lakes, mosquitofish to the American southwest and the tropics worldwide, etc. etc., not to mention the continued stocking of non-native gamefish worldwide.
California's native fishes have and continue to be devestated by deliberate, state-sponsored, biologist-approved introductions of fish from eastern North America and Eurasia, as well as accidental and illegal introductions by the state's residents and visitors. This particular case is one of an unofficial introduction, the Northern Pike, interfering with the state's planned introduction, Rainbow Trout, in an ecologically dead lake. It was largely an economic problem rather than an ecological one, though there was concern that the pike could escape to the Sacramento River and cause serious damage to the native fish still dwelling there, particularly salmon.
You all might be interested to learn that this effort has already been carried out, apparently successfully: see
this article for more details.
I found this information interesting:
linked article said:
Prior to the September treatment, the pike had ravaged the trout population. After the lake was treated with rotenone, DFG workers collected over 50,000 pounds of fish. About 10 percent were northern pike, 83 percent were brown bullheads and less than 1 percent (.6 percent) were rainbow trout. The remaining 6 percent included largemouth bass, golden shiners and pumpkinseed sunfish, according to Randy Kelly, DFG Project Manager.
For those of you who don't know, brown bullheads, northern pike, largemouth bass, golden shiners, and pumpkinseed sunfish are all eastern species that do not naturally occur west of the Rockies, i.e. they are all introductions. The trout in Lake Davis, though a species native to the west coast, were all introduced as well. That's right, there were NO native fish affected by this operation.