That's a strange use of "adapted", there. The logic here seems to be:

"Sure, salmon and trout numbers have gone down -- but not all runs have been completely wiped out. Therefore, they have "adapted" and there's really nothing to worry about. All so-called scientists talking about a 98 percent reduction in return counts since 1880, and warning that some runs are on the verge of extinction due to the combined effects of habitat reduction and climate change -- they have no idea what they're talking about, really."