Overfishing Leads to Domino Effect that Can Harm Ecosystems for Generations, New Meta-Analysis Suggests

A new study in the Proceedings of the National Academy of Sciences highlights the interconnectedness of marine ecosystems and the snowball effect that can be caused by overfishing.

Study co-author Felicia Coleman, director of the Florida State University Coastal and Marine Laboratory, examined data from fisheries with her colleagues and determined that there is indeed a domino-effect that is triggered when numbers of key fish species get too low.

The researchers looked at several overfishing case studies to assess the ecological effects brought on to marine environments.

The Northern Benguela ecosystem off the coast of Namibia, for example, saw great changes in the 1970s when stocks of anchovy and sardines collapsed from overfishing.

As populations of those fish dropped, the ecosystem became saturated with bearded goby and jellyfish. These creatures, while numerous, were not calorically dense enough to support other animals in the ecosystem that thrived off sardines and anchovy, such as penguins, gannets and hake.

Since the 1970s, populations of African penguins and Cape gannets have declined by 77 percent and 94 percent, respectively. Production of Cape hake and deep-water hake fell from 725,000 metric tons in 1972, to 110,000 metric tons in 1990. And the population of Cape fur seals has fluctuated dramatically, the researchers said.

"When you put all these examples together, you realize there really is something important going on in the world's ecosystems," said FSU biological science professor Joseph Travis, a study co-author. "It's easy to write off one case study. But, when you string them all together as this paper does, I think you come away with a compelling case that tipping points are real, we've crossed them in many ecosystems, and we'll cross more of them unless we can get this problem under control."

The researchers said they hope their work will will accelerate changes in how the fishing industry conducts itself.

"It's a lot easier to back up to avoid a tipping point before you get to it than it is to find a way to return once you've crossed it," Travis said.

Coleman added the fishery managers generally understand how overfishing affects species and the overall ecosystem, but that those topics, as a whole, need "to be a bigger part of the conversation and turned into action," Coleman said.