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Fast-Growing Fish Are Hit Hardest by Overfishing

On land, the fastest-growing animals can adapt quickly to changing environments, but the same advantage doesn't carry over into marine ecosystems.
Edge of a horse-eye jack baitball. (Photo: Epipelagic/Wikimedia Commons)

Edge of a horse-eye jack baitball. (Photo: Epipelagic/Wikimedia Commons)

Not since the dinosaurs began to die-off 65 million years ago have we seen such a rapid disappearance of species on Earth. But not all species will face such a bleak future, it seems. On land, the fastest-growing animals have an edge; up to a point, they are able to reproduce at rates that can offset their species' demise. Slow-growing species, meanwhile, are more vulnerable. But in the ocean, the opposite is true: Fast-growing populations are just as likely, or more so, to collapse. In a new study, a team of researchers from Rutgers and Princeton universities set out to discover why.

The researchers looked at more than 150 populations of fishing stocks across 25 coastal and open ocean marine ecosystems. They found that a quarter of the populations experienced a collapse over the last half-century—meaning the number of fish dropped to below 20 percent of the necessary amount for a sustainable population. To find out what caused the declines, the researchers used statistical tests to tease out the contributions of short- and long-term climate variability and overfishing in each ecosystem.

The team reported yesterday in Proceedings of the Royal Society B: Biological Sciences, that, in overfished populations, fast-growing species, such as flounder and sardines, had triple the risk of their populations crashing. Further, overfished populations in ecosystems in unstable climates were twice as likely to collapse than those in stable climates. Fast-growing fish can usually respond rapidly to environmental change, but overfishing can make these species more sensitive to climate change by shortening the age distribution of a population, reducing diversity, and destroying habitats. The study suggests that despite the sensitivity of marine species to climate change, overfishing was the main driver of declines in fishing stocks over the last 50 years.

The bad news is that humans are mostly to blame here. But there's good news, too; that means better management practices could go a long way to stabilize these fish populations. And an added bonus: Previous research shows that even minor fishing restrictions could help the world's endangered reefs bounce back.