Field Application of Rigid Endoscopy for Determining Gender, Reproductive Status, and Disease in Free-Ranging Endangered Sturgeon (Scaphirhynchus spp.) From the Mississippi River
The shovelnose (Scaphirhynchus platorynchus) and pallid sturgeon (Scaphirhynchus albus) are both threatened species due to habitat loss and commercial pressures for an alternative source of caviar. Intensive research and management efforts by federal and state organizations have been underway since 1990 in an attempt to determine and stabilize free-ranging populations. One important aspect of evaluating population dynamics includes detailed life history, and in particular survivorship, recruitment, reproduction, and disease. Identification of gender and determination of reproductive status has been an area of intense interest for ichthyologists studying this monomorphic species.1-4
Forty-three sturgeon were caught from the Mississippi River in Tunica, MS using baited hooks, and transferred to temporary holding nets. All fish were consecutively anesthetized using 90 mg/L buffered tricaine methanesulfonate (Tricaine-S, Western Chemical Inc., Ferndale, WA, USA) for coelioscopy using a Tele Pak and 2.7-mm telescope system (Karl Storz Veterinary Endoscopy, Goleta, CA, USA). Following a 3-mm stab incision in the ventral midline approximately midway between the pelvic and pectoral fins, a 2.7-mm telescope housed within a 14.5-Fr operating sheath was inserted into the coelom. Coelomic insufflation was achieved using sterile saline delivered by infusion line to one of the sheath ports. Gender and reproductive status were determined, and confirmed by gonadal biopsy. Saline was manually evacuated using external pressure, and in select females sonic transmitters were inserted before closure. All fish recovered uneventfully and were successfully released.
Coelioscopy offered unparalleled visibility of the gonads compared to previously described endoscopic and ultrasonographic procedures, and was able to consistently identify gender and accurately stage reproductive status.2,4 Coelioscopy is recommended as a minimally invasive technique for the field determination of fish gender and reproductive staging.
1. Hurvitz, A., K. Jackson, G. Degani, and B. Levavi-Sivan. 2007. Use of endoscopy for gender and ovarian stage determinations in Russian sturgeon (Acipenser gueldenstaedtii) grown in aquaculture. Aquaculture. 270:158–166.
2. Bryan, J.L., M.L. Wildhaber, D.M. Papoulias, A.J. DeLonay, D.E. Tillitt, and M.L. Annis. 2007. Estimation of gonad volume, fecundity, and reproductive stage of shovelnose sturgeon using sonography and endoscopy with application to the endangered pallid sturgeon. J. Appl. Ichthyol. 23:411–419.
3. Wildhaber, M.L., D.M. Papoulias, A.J. DeLonay, D.E. Tillitt, J.L. Bryan, and M.L. Annis. 2007. Physical and hormonal examination of Missouri River shovelnose sturgeon reproductive stage: a reference guide. J. Appl. Ichthyol. 23:382–401.
4. Wildhaber, M.L., D.M. Papoulias, A.J. DeLonay, D.E. Tillitt, J.L. Bryan, M.L. Annis, and J.A. Allert. 2005. Gender identification of shovelnose sturgeon using ultrasonic and endoscopic imagery and the application of the method to the pallid sturgeon. J. Fish Biol. 67:114–132.