Ever since the first time I saw Star Trek IV in the theatres I've always wondered if the extinction of humpback whales wasn't caused by Star Fleet itself.

There is a need for humpback whales in the future to protect earth from a probe that somehow transmits sound through the vacuum of space (let's not get started on that) but after Kirk and co. are successful in bringing extinct whales from Earth's past into their present surely their biologists realized there would be no way to repopulate an extinct species with only three specimens. So it would be necessary for Star Fleet to send more missions to the past to load up on humpbacks. Since in the future humpbacks are extinct every humpback you bring to the future is a humpback you save from inevitable extinction. This would create a sense of moral urgency to "save" every humpback you could. The more humpbacks you retrieve the better it is for their species.

But what if the extinction of humpbacks in the past is caused because Star Fleet's harvesting of whales plus past human harvesting meant there was not a biologically viable breeding population of whales in the past.

This for me was always a bigger temporal paradox than the one about Kirk's glasses.