There are many unknowns.
Please add posts that not many would know.
Recently have become fascinated about salmon.
There is a remote archipelago known as The Kerguelen Islands,south west of Africa.
Salmon were introduced to these islands early 1900s.
The Salmon have thrived and have colonised new rivers on there own.
They also introduced reindeer,which have also thrived.
https://en.wikipedia.org/wiki/Kerguelen_Islands