Determining Age of Atlantic Shad from their Scales

Type: Chesapeake
Region:
Location: Kent Island

During the spring sampling scales are taken from adult Shad to analyze age and spawn marks. These pieces of data can help in understanding the age-class compositions of Hickory and American Shad populations in different Chesapeake Tributaries.

Once scales are cleaned, they are mounted on glass slides and viewed using a Microfiche reader. The scale is enlarged on the reader, and examined for age and spawning marks. Age is determined by looking at growth annuli on the scales, similar to rings on a tree. Spawning marks are scarlike rings on the outer portion of the scale. The marks are created during the spring spawning runs as a result of consuming little or no food. When shad return to their feeding grounds in salt water, normal scale growth resumes.

The scale pictured below was from a female Hickory Shad captured in the Susquehanna River. From the scale I was able to conclude that this fish is 9 years old and has made five spawning runs to its natal Susquehanna River.

Source-
Cating, J.P. 1953. Determining Age of Atlantic Shad from their Scales. Fishery Bulletin 85, Fishery Bulletin of the Fish and Wildlife Service, Volume 54.