How long did a person have to be missing before they could be declared dead? Different countries had different regulations on the issue. Generally speaking, it was around three or five years, though there were some that had a shorter, or longer, time frame.
So, how long until a missing whale could be declared dead? It was hard to say.
The whale, known as "52 Hertz" because of its unique sound frequency band, had been discovered in 1989. That meant it was at least 30 years old.
Generally, the lifespan of whales was very long, much longer than 30 years, but too many things could happen in that timeframe.
People had not heard its sound since 2004, which was 15 years after it was first discovered.
