Wednesday, April 01, 2009

Terminal Cretaceous Fish Extinction Explained

Ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinctionz. 2009. M. Friedman. PNAS, Published online before print March 10, 2009.

Painting by Dan Erickson
Large size and a fast bite spelled doom for bony fishes during the last mass extinction 65 million years ago.
Today, those same features characterize large predatory bony fishes, such as tuna and billfishes, that are currently in decline and at risk of extinction themselves, said Matt Friedman.

"The same thing is happening today to ecologically similar fishes," he said. "The hardest hit species are consistently big predators."

Studies of modern fishes demonstrate that large body size is linked to large prey size and low rates of population growth, while fast-closing jaws appear to be adaptations for capturing agile, evasive prey—in other words, other fishes. The fossil record provides some remarkable evidence supporting these estimates of function: fossil fishes with preserved stomach contents that record their last meals.

Scientists had speculated that during that Cretaceous extinction predatory fishes might have been more likely than other fishes to go extinct because they tended to have slowly increasing populations, lived more spread out, took longer to mature, and occupied precarious positions at the tops of food chains. Today, ecologically similar fishes appear to be the least able to rebound from declining numbers due to overfishing.

Ironically, today's large fishes with fast bites evolved relatively shortly after the end-Cretaceous extinction, apparently filling the functional and ecological roles vacated by the victims of that mass extinction. Although the two groups of fishes are not related to each other, their fates may end up being similar. link