Status of the imperiled Alabama Sturgeon (Scaphirhynchus suttkusiWilliams and Clemmer, 1991)

Abstract

Summary The Alabama Sturgeon (ALS) Scaphirhynchus suttkusi has the smallest maximum size (78 cm FL), most restricted native range (the Mobile Basin, restricted to large coastal plain rivers), and the lowest abundance of any North American sturgeon. This riverine species is currently restricted to 524 RKM in the lower Cahaba and Alabama rivers in south Alabama. A commercial fishery existed in the 1890s, and it was still ‘not uncommon’ in Alabama in the 1930s. However, by the 1980s there was a sharp decrease in reports and confirmed collections of ALS. The recent collapse is due to loss and fragmentation of free-flowing riverine habitat and blockage of migratory routes due to construction of dams. Since 1997, state and federal agencies have collected only six individuals while expending over 3000 personnel-da in effort. Propagation efforts have proven unsuccessful to date. The last sighting of an ALS (not captured) was by Alabama Department of Conservation and Natural Resources (ADCNR) fisheries biologists in the Alabama River in April 2009. The last confirmed collection of an ALS occurred in April 2007. This specimen was implanted with a sonic tag, providing valuable habitat and movement data. Very little is known about life history or population structure of this species. Controversy surrounded designation of the ALS as federally endangered in the U.S. under the Endangered Species Act, with a business-oriented coalition challenging the listing through the federal circuit court of appeals. Recovery efforts are focused on obtaining individuals for propagation and providing fish passage through navigation locks on the Alabama River, although this option may not be viable for the ALS. The outlook for the ALS is bleak unless adequate number of individuals can be collected for propagation, access can be provided to historical spawning grounds in the lower Cahaba River, and flow and habitat can be restored to meet life history requirements. However, preliminary results from environmental DNA (eDNA) analysis in 2015 detected the presence of ALS in the Alabama River and may guide future collection efforts.