I wish I had specifics, but I believe they have moved animals from time to time. (both to AK and from AK.)
A key reason to move animals between accredited zoos is to increase genetic diversity. In some cases, artificial insemination is an option, but I'm not sure that is an option for every endangered species. Inbreeding is very a common zoo problem.
The Nat Geo channel has multiple shows about zoos, and animal care. There are a number of reasons why animals move between zoos. Sometimes a zoo or exhibit closes, sometimes they breed more animals than they can have room to keep.
If you wish to watch a show that is both interesting and not depressing, there was a series on PBS about rewilding Europe, called Europe's New Wild. Rewilding means reintroducing species back into the wild, or back into areas where they had previously been extinct, or nearly extinct. One episode, for example, details how lynx were bred for the purpose of reintroducing them to the wild. I have no idea if AK participates in any rewilding efforts, but that's the very best reason to move animals from any zoo. IMO.
Sadly, rewilding is very rare. Generation after generation of zoo animals live their entire lives in zoos.