Oceans in the Old Days Had Way Bigger and More Fish Than We Thought

giant ocean fish photo

Photo via Mike Johnston via Flickr CC

It's a no brainer that as game fish species are overfished, the species sizes would shrink. But a new census project highlights just how dramatically the ocean's fish species have diminished in both size and diversity over a relatively very short period of time. Researchers are using all the material they can get their hands on, from ship logs to literary text to business documents to help them recreate what fish populations were like back in the day. And the image they're finding shows just how much populations and species sizes have diminished.

From the release:

Before oil hunters in the early 1800s harpooned whales by the score, the ocean around New Zealand teemed with about 27,000 southern right whales - roughly 30 times as many as today - according to one of several astonishing reconstructions of ocean life in olden days to be presented at a Census of Marine Life conference May 26-28.

At about the same time, UK researchers say large pods of blue whales and orcas, blue sharks and thresher sharks darkened the waters off Cornwall, England, herds of harbour porpoise pursued fish upriver, and dolphins regularly played in waters inshore.

The old documents are shifting what scientists currently think of as average species size, showing that fish used to be much larger, and in larger populations than we thought. And while researchers are trying to go back to centuries and even thousands of years in the past, we don't have to go that far to see proof that their recreations are probably pretty accurate. Here is an image showing catches of gamefish in the Florida Keys - they're smaller, and less diverse over just the last 60 years.

The scientists are hoping that by showing what kind of life the oceans used to hold, and the impact overfishing has had, that a marine recovery will be that much more possible.

"Forecasting and backcasting are two sides of the same coin," says Jesse Ausubel, Program Director of the Census at the Alfred P. Sloan Foundation. "Analytic tools developed by ecologists to predict future abundance have been adapted to reconstruct histories of marine life...

...We now know that the distribution and abundance of marine animal populations change dramatically over time. Climate and humanity forces changes and while few marine species have gone extinct, entire marine ecosystems may have been depleted beyond recovery.

Understanding historical patterns of resource exploitation and identifying what has actually been lost in the habitat is essential to develop and implement recovery plans for depleted marine ecosystems."

More on Overfishing
Global Fisheries Hit by Climate Change and Overfishing
Overfishing Means Marine Animals Are Starving: Report
Monterey Bay Aquarium's Endangered Seafood Guide

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