In 2012, most Atlantic sturgeon populations, including the Carolina distinct population segment, became federally listed as endangered under the Endangered Species Act. The Alligator River Bridge on US64 is slated to be replaced by 2029. Being listed as an endangered species, federal and state resource agencies were concerned over potential impacts of bridge construction on feeding juvenile or adult migrating sturgeon within the Alligator River, NC. Atlantic sturgeon presence within the Alligator River Bridge area was sparce and more information was needed to make informed decisions.
The main goal of this research was to determine Atlantic sturgeon presence within the Alligator River with a focus on the bridge area prior to the onset of construction. In order to elucidate presence, Atlantic sturgeon needed to be collected, telemetry tagged, and tracked throughout the Albemarle Sound/Alligator River area.
From April 2021 to April 2026, sixty juvenile and 22 adult Atlantic sturgeon were tracked throughout the Albemarle Sound Complex, including the Alligator River. During that time period, the tagged juveniles spent a combined 15,816 days within the Albemarle Sound with 54 days (0.3%) within the Alligator River Array. The tagged adults were within the Albemarle Sound 6970 days and were detected a combined 16 days (0.2%) within the Alligator River Array. The telemetry data show that the Alligator River is a rarely utilized area for feeding juveniles and staging adults. The Alligator River appears to not be a staging area because both adults staging for spawning and feeding juveniles tend to inhabit areas closer to the saltwedge which is often located in the western part of the Albemarle Sound.
Due to an accelerated work schedule, pile-driving for the new Alligator River Bridge supports started while the project was on-going. From February 18th, 2025, to February 12th, 2026, pile driving operations for bridge support bents occurred at the Alligator River Bridge area.
Unfortunately, by this time a majority of the telemetry tag batteries in the juveniles tagged were no longer active or fish left the system entirely. It was also a dry year; therefore, juveniles and adults were squeezed even further in the very western part of the Albemarle Sound.
However, one juvenile tagged on December 14th, 2023, was detected at the two receivers adjacent to the Alligator Bridge on May 13th, May 15th, and November 13th, 2025. Pile driving did not occur during May 13th but did occur during May 15th and November 13th.
Fine scale fish positioning is not available based on receiver deployment. Pile driving occurred at two different locations on May 15th and three different locations on November 13th. Based on tag detection range and pile driving location, the juvenile was likely within 2km of pile driving operations, did not immediately leave the area during pile driving, and was later detected in the western Albemarle Sound.
Another goal of this work was to collect genetic samples to help improve on previous genetic classifications on Atlantic sturgeon inhabiting the Albemarle Sound. Genetic samples from adults and juveniles collected during this project enabled refinement of the Roanoke River fall population designation plus showed over 83% of the subadults within the Albemarle Sound are of the Roanoke fall population.
