February 15-18, 2009 Washington State Convention Center Seattle ...

4
EVALUATION OF THE USE OF ULTRASOUND TO STAGE MATURE WHITE STURGEON
Acipenser transmontanus FOR CAVIAR PRODUCTION
Brian C. Donahower*, Steve DuMond, Leo Ray, Linda Lemmon, Gary Fornshell, Terry Patterson, Jodi Rockett,
Madison S. Powell and Wendy M. Sealey
Hagerman Fish Culture Experiment Station
University of Idaho
3059F National Fish Hatchery Road
Hagerman, ID 83332 USA
donahower@uidaho.edu
Currently, the only means to assess ripeness of white sturgeon females and properly time harvest is measurement of oocyte
polarization index (PI). This technique requires minor abdominal surgery, is time consuming, and not an effective tool for
handling a large number of fish. Hence, oocyte PI is generally used only once in the fall to predict the timing of harvest of females
later in the winter and spring. This often results in an improper timing of harvest, decreasing caviar yield and quality, and
increasing the rate of follicular atresia (resorption of eggs). New methods to stage sturgeon for caviar production are needed to
replace the use of oocyte PI. These methods should be non-invasive, if possible, and quick.
Ultrasound has been employed in the medical field and terrestrial animal agriculture for several decades to non-invasively assess
soft tissue within live animals. Ultrasound is defined as acoustic energy produced by a transducer at megahertz frequencies.
As the wave energy passes through tissues, energy is scattered, absorbed or reflected back to the transducer depending on the
properties of the tissue and the relative changes of those properties between tissues.
To assess the utilization of ultrasound, 54 adult female white sturgeon and 4 adult male white sturgeon were scanned along the
abdomen in the transverse and sagittal planes. Ultrasonic images were captured at multiple sections along the left and right abdominal
walls between the pelvic and pectoral fins. Using ultrasound for initial evaluation, roughly half of the female sturgeon
were identified as having a distinct, mature egg mass on one or both sides of the abdomen. These findings were confirmed by
biopsy. Additionally, egg size was measured using the ultrasonic measurement tool and following biopsy with mixed results.
Female sturgeon not displaying clear signs of mature eggs using ultrasound were proven to have immature or atritic eggs.
While the number of male sturgeon examined was substantially less than female sturgeon, the presence of testes was unambiguous,
though the occurrence of large fat deposits surrounding the gonads made the detection of testes more difficult compared to
detection of female sex tissue. Preliminary results indicate that use of ultrasound can be an effective and non-invasive method
of sexing mature sturgeon and ascertaining the maturity of ovarian tissue in adult female sturgeon, though further analysis and
examination is warranted.