Biodiversity on the Cahaba

Biodiversity on the Cahaba
and what we’re doing to PRESERVE it.

The Cahaba River is world-renowned for the amazing biodiversity it supports.  Historically, the Cahaba supported at least 134 species of fish, rivaling any river of its size in North America.  

Unfortunately, a variety of threats have already reduced that number, with more fish added to the list of threatened or endangered species frequently.  Those threats include the dams on the lower Alabama River, siltation, pathogens, and habitat loss.   What is clear with each new listing is the reality that state and federal agencies do not have the necessary data to understand the current status of many fish, or the mussels that depend on them, creating a significant barrier for efforts to preserve them.

The Alabama Sturgeon (Scaphirhynchus suttkusi)

By Patrick O’Neil, , Geological Survey of Alabama – http://gallery.usgs.gov/photos/360, Public Domain, https://commons.wikimedia.org/w/index.php?curid=19859076

Perhaps no species illustrates this problem more clearly than the Alabama Sturgeon, a critically endangered fish that once used the Cahaba River as a nursery for young fish that would one day return to the larger coastal plain rivers of the Mobile Basin.  The Alabama Sturgeon is native to Alabama and was first described in the 1950’s, but not formally recognized as a distinct species until 1991.  The sturgeon inhabited about 1,000 miles of rivers in the Mobile Basin, but is now believed to inhabit less than 130 miles of the lower Alabama river, if it remains at all.  

By the 1990’s, the Alabama sturgeon was rarely seen, and industry groups opposed the United States Fish and Wildlife Service’s (USFWS) efforts to list the species as threatened or endangered and the effort was abandoned. Fortunately, environmental lawyer Ray Vaughan successfully sued the USFWS to list the Alabama sturgeon and in 2000 it was formally listed.  The last collection of a live fish was on April 3rd, 2007. 

In 1898, the Alabama commercial fishing report documented the harvesting of approximately 20,000 individuals, providing some record of how common sturgeon once were in the rivers of Alabama.  Between 1997 and 1999, more than 4,000 man hours were expended during efforts to find the species, resulting in the collection of only five fish, three of which died in captivity.  Since that time, thousands of hours have been dedicated to locating live specimens, which have proven futile.  As a result, state agencies have been unable to breed this fish in captivity, limiting any chance of species recovery.

There is no conclusive data on the feeding, spawning, or migratory habits of the species, making efforts to find and preserve it challenging.  

To learn more about the Alabama Sturgeon, visit:  https://www.fws.gov/species/alabama-sturgeon-scaphirhynchus-suttkusi

What are we doing to help?

Cahaba Riverkeeper is committed to preserving the biodiversity of the Cahaba river, and was inspired by the story of the Alabama sturgeon to evaluate and employ new techniques and technology to help fill the data gaps that exist for many Alabama species.  

While exploring potential methods that could help locate rare fish, we were exposed to the relatively new science around environmental DNA.  Environmental DNA is organismal DNA that is shed by organisms (skin, feces, etc..) and can persist in the environment for between 7 and 21 days, making it possible to detect where a particular species may be present.  This allows more targeted sampling, reducing the burden on state and federal agencies to survey large areas.

In 2019, Cahaba Riverkeeper began collecting eDNA samples along the Cahaba river, preserving two samples at each location to provide a sample for current analysis, as well as one that could be analyzed in the future as analysis becomes more accurate and inexpensive.  The creation of this time capsule of samples allows us to contribute useful information to state and federal agencies to help inform regulatory policy decisions both today and in the future.  To date, despite collecting hundreds of samples, we have not confirmed the presence of the Alabama sturgeon in the Cahaba river.  However, we have provided the data collected for a variety of studies, including the USFWS study of the Coal Darter (Percina brevicauda), which was proposed to be listed as threatened in 2023.

Your investment in our work helps ensure that we can continue to collect high quality data to influence state and federal policy decisions that are critical to the protection of the amazing biodiversity found in the Cahaba river.  Currently, there are dozens of species proposed to be listed, which has created enormous challenges for the agencies tasked with providing data to inform each potential listing.  With your support, we’ll continue our efforts to ensure as many of these species survive for future generations. 

Please consider a donation today to support this critical work:  www.cahabariverkeeper.org/donate

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