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Drought, Loss of Habitat behind Declining Native Fish Populations in US

Jun 08, 2013 06:43 AM EDT

There has been a dramatic decline in the populations of native fish in the U.S., mostly due to drought and loss of habitat, according to a Kansas State University researcher.

"A couple of key species that we have been studying have virtually disappeared where they historically were abundant," said Keith Gido, professor of biology who researches fish ecology and conservation of aquatic systems.

In the summer of 2011, Gido and his team found about 300 silver chub in the Ninnescah River in southern Kansas, which declined to three by the summer of 2012 and zero in 2013.

"We are in a conservation crisis," Gido said in a news release. "Our fish communities have changed dramatically and we are losing a lot of native species."

Warm climate has been linked with native fish disappearance in other parts of the country. A recent study had found that about 82 fish species in California will be extinct by the end of this century.

According to Gido, river fragmentation and groundwater withdrawals are the main factors behind the declining population of fish species in the Great Plains. The recent drought has increased the effects of these two factors and has reduced the fish diversity in this region.

River fragmentation is when dams and other man-made barriers break the river into several shorter parts. This breaking up of a river makes it impossible for some species of fish to survive.

Also, non-native fish thrive in reservoirs and ponds, and these fish not only compete with native fish for resources, but also actively prey on them.

"As the water levels decline, if you have a nonnative predator in the system, then the predators' effects are much stronger and have a more drastic effect on fish. We have seen a gradual decline in native diversity over time. The drought exacerbates any of the effects because with fragmentation, if the stream is dry and the water is lower, the fish are unable to move around a barrier," Gido said.

Gido said that removing the non-native fish during drought could give the native fish a chance to survive.

The research is published in the journal Fisheries.                                             

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