From: PeerJ
Published December 12, 2017 12:53 PM

Native Fish Species at Risk Following Water Removal from the Colorado River

Agriculture and domestic activities consume much of the Colorado River water that once flowed to the Colorado Delta and Northern Gulf of California. The nature and extent of impact of this fresh-water loss on the ecology and fisheries of the Colorado Delta and Gulf of California is controversial. A recent publication in the journal PeerJ reveals a previously unseen risk to the unique local biodiversity of the tidal portion of the Delta. 

Unique ecological species evolved in the historically fresher Colorado Delta and adapted to this environment. These fish are distinct from closely related species in the historically saltier estuaries found in other regions of the Gulf. However, the Colorado Delta is now more similar in salinity to many of the other estuary systems in the Gulf of California, suggesting that the ecological factors that separated species may have broken down.

Workers from UCLA examined species of silverside fish in a genus that only occurs in the Gulf of California. One species, Colpichthys hubbsi, lives exclusively in the Delta and is listed as endangered due to its restricted range. Morphologic and genetic anayses demonstrate that this species hybridizes along the western edge of the Delta with Colpichthys regis, a widespread relative distributed in estuaries throughout the Gulf. Although hybrids could be recognized morphologically, there was no evidence of hybridization in earlier museum collections. 

Read more at PeerJ

Image: Jars of preserved fish specimens from the Scripps Institution of Oceanography used in this study. (Credit: Clive Lau)

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