Yellow River Sturgeon Research

     The Gulf sturgeon is a large anadromous fish species, listed as threatened under the Endangered Species Act in 1991. Gulf sturgeon inhabit coastal rivers from the Suwannee River, Florida to the Pearl River, Louisiana. Accurate assessment of Gulf sturgeon populations, and factors affecting populations, is a necessity for the recovery of the species.

     The United States Fish and Wildlife Service is currently funding a three-year project to assess the population of Gulf sturgeon inhabiting the Yellow River.  The Yellow River is a coastal river draining into Blackwater Bay near Milton, Florida, with headwaters beginning in Conecuh National Forest near Andalusia, Alabama. The goals of the study are to estimate population size of the Yellow River population through the use of tag-recapture data. Life history parameters, including mortality, survivability and recruitment will also be examined.  We use a wide range of sampling gears to capture sturgeon.  Each sturgeon that is captured is weighed, measured, and tagged to allow for individual identification.  We use both PIT tags and Floy tags. PIT tags are electronic tags, approximately the same size as a grain of rice, and are injected in the dorsal musculature of the fish, just below the dorsal fin. Floy tags are numbered tags that are inserted through the pectoral fins. Multiple tags in the same fish help to insure accurate identification of any recaptured fish, alleviating any problems with tag loss. Population size and survival are being assessed using Cormack-Jolly–Seber (CJS) type models based on individual fish recapture histories.

     A section of the leading edge of the first pectoral fin-ray is removed to be aged back at the laboratory. In the lab, sections are cut using a low-speed isomet saw with a diamond-wafering blade.  After sectioning, the age of the fish is determined using a dissecting microscope. Sturgeon, like many species of fish, lay down annular rings in their bony parts (i.e., fin-rays and otoliths).  The main advantage of using fin-rays over otoliths is that fin-ray aging is non-lethal and the fish do not have to be sacrificed. Sections of fin-ray and otolith can be used to age sturgeon by counting rings, as you would a section from a tree.

     We are also currently investigating underestimation of fish aging using pectoral fin-rays. We are using fin-rays that were removed from deceased fish in the late 1980's and early 1990's. The entire leading pectoral fin-ray was removed from dead fish, which allows us to section the fin-ray at numerous locations in an attempt to calculate the number of years (rings) that are lost as you move away from the point where the fin meets the body of the fish.

Gulf Sturgeon Facts
Additional Images from Field Sampling on the Suwannee River.

For more information, contact:
Jim Berg - jim_berg@usgs.gov