Large-River Fish May Benefit From New Conservation Approach

Fishes that find their home in large-rivers — such as paddlefish, blue catfish, crystal darters, silver chub, etc — are largely headed towards extinction in the US as a result of habitat loss. But now, new research is suggesting that by utilizing a different approach to conservation that there is “hope” for them.

Image Credit: Brenda Pracheil
Image Credit: Brenda Pracheil

The new research from the University of Wisconsin-Madison estimates that 60 out of 68 US species, or 88% of the fish species that are found only in large-river ecosystems like “the Mississippi, Missouri and Ohio rivers, are of state, federal or international conservation concern. Traditionally, the conservation emphasis has been on restoring original habitat. This task proves impossible for ecosystems like the main trunk of the Mississippi River — the nation’s shipping, power production, and flood control backbone. While the locks, dams and levees that make the Mississippi a mighty economic force have destroyed fish habitat by blocking off migration pathways and changing annual flood cycles species need to spawn, removing them is not a realistic conservation option.”

But, according to researcher and lead author of the new study, Brenda Pracheil, “We’re underestimating the importance of tributaries.” As the new research has found, for the species’ specially adapted to large-river ecosystems it isn’t an all or nothing situation. Some smaller rivers “are just big enough to be a haven. For any river in the Mississippi Basin with a flow rate of less than 166 cubic meters of water per second, virtually no large-river specialist fishes are present. But in any river that even slightly exceeds that rate, 80% or more of the large-river species call it home.”

What that means is that Mississippi tributaries roughly around the size of the Wisconsin River are ale to provide “crucial habitat for large-river fishes. When coupled with current efforts in the large rivers themselves, these rivers may present important opportunities for saving species.”

“Talk to any large-river fish biologist, and they will tell you how important tributaries are to big river fish,” says Pracheil. “But, until now, we’ve not really understood which rivers are most important. Our study tackles that and shows which tributaries in the Mississippi River Basin show the most promise for conservation of large-river fishes.”

“Current policies governing large river restoration projects are funded largely through the US Army Corps of Engineers, which requires that funds be spent on mainstems — or the big rivers themselves. Pracheil’s study suggests spending some of that money on tributary restoration projects might do more conservation good for fish, while also letting agencies get more bang for their habitat restoration buck.”

“Tributaries may be one of our last chances to preserve large-river fish habitat,” Pracheil says. “Even though the dam building era is all but over in this country, it’s just starting on rivers like the Mekong and Amazon — places that are hotspots for freshwater fish diversity. While tributaries cannot offer a one-to-one replacement of main river habitats, our work suggests that [they] provide important refuges for large-river fishes and that both main rivers and their tributaries should be considered in conservation plans.”

The new research was recently published in the April issue of the journal Frontiers in Ecology and the Environment.

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