I just finished reading Ringworld (published October, 1970), in which at one point a main character wonders whether any whales were taken from Earth before they went extinct. According to the Known Space Correspondence,
Blue whales and sperm whales were extinct on Earth by 2850.
Reference: Ringworld ch. 24
What was the first science fiction work in which whales are predicted to go extinct?
Further qualifications: the extinction doesn't necessarily need to be tied to an environmental message, but it does need to specifically mention whales in order to qualify. I'm asking this question because I'm interested in when whales became a symbol of environmental fragility, or at the very least the natural transience of species. So a future in which "whales, dolphins, and jaguars" are extinct would qualify, but one in which "all life in the ocean" or "all life on Earth" is wiped out would not.
Addendum: let's hope they're all wrong :(