Fish populations in the world’s oceans are getting younger as a result of humanity’s growing appetite for seafood.
Lewis Barnett at the University of Washington in Seattle and his colleagues looked at stock assessments for 63 fish populations spanning 5 ocean regions. Compared with historical records, the percentage of fish in the oldest age class has declined in about 80% of populations, with around one-third seeing declines of more than 90%. The effect was even more pronounced when the team predicted likely population numbers if species had not been fished at all, and compared these with the existing percentage of old fish.
A shift towards youth affects productivity and can harm the stability of populations. And the decrease in the number of mature fish makes populations less diverse and more vulnerable to environmental challenges, the authors say.