A study published in Theoretical Ecology earlier this Spring suggests that invasive species find a foothold in new ecosystems by hanging out at familiar landmarks. Species such as the Asian carp, when finding themselves in a new environment, will seek out spots that look different, in the hope that a potential mate will have the same idea.
On this basis, if ten fish were dropped at different points into a water the size of Loch Ness, then they would find one another and thereafter breed. Of course, this is utter bunkum – any fish dropped into Loch Ness would be scoffed by Nessie long before they managed to copulate…