Nineteen million years ago, shark populations declined by 90%, and nobody knows why.
A scientist from Yale discovered the unknown extinction event while studying fossilized teeth and scales. The data revealed that both total population and species diversity plummeted about 19 million years ago. There was a 90% abundance reduction and a 70% diversity reduction.
The problem? There’s no evidence of any particular cause or event.
The decline in shark numbers took place over 100,000 years. A long time for us, but a blink in the geological record—it’s considered a “sudden” disappearance.
Causes of other mass extinction events aren’t so murky—for example, scientists know the asteroid obliterated the dinosaurs.
What if a scientist identified the mass extinction's cause and discovers another one is about to start within our lifetime?
A 100k year period is a long time for a story, so I’ll assume the extinction event will take ten years. And that there is something humans can do about it.
Additionally, too many people don’t care about sharks. But what about all fish? A fish pandemic—humanity’s response could mirror the response to COVID-19. It strikes coastal waters at a higher rate than the deep ocean, purely based on population density.
The main character is a United States-based scientist. She has to deal with half the scientific establishment denying the existence and severity of the pandemic in the first place.
She works closely with scientists from other countries, particularly Central and South American researchers. They come up with a cure that infringes on United States patents. If they can get a certain number of fish the vaccine, the virus won’t spread.
The majority of the story could take place on a ship. The battle could be the legal action that grants the right to produce the “vaccine,” only to find themselves stopped by a United States naval blockade.
Since the well-intentioned scientists can’t move, the fish start coming to them. They vaccinate all the fish they can and wait. Cut to years later, and it turns out the fish in Central and South America have all survived—the fish population closest to the United States is declining rapidly, and the establishment still denies the virus.