Estimation of gonad volume, fecundity, and reproductive stage of shovelnose sturgeon using sonography and endoscopy with application to the endangered pallid sturgeon

Abstract

Most species of sturgeon are declining in the Mississippi River Basin of North America including pallid (Scaphirhynchus albus F. and R.) and shovelnose sturgeons (S. platorynchus R.). Understanding the reproductive cycle of sturgeon in the Mississippi River Basin is important in evaluating the status and viability of sturgeon populations. We used non-invasive, non-lethal methods for examining internal reproductive organs of shovelnose and pallid sturgeon. We used an ultrasound to measure egg diameter, fecundity, and gonad volume; endoscope was used to visually examine the gonad. We found the ultrasound to accurately measure the gonad volume, but it underestimated egg diameter by 52%. After correcting for the measurement error, the ultrasound accurately measured the gonad volume but it was higher than the true gonad volume for stages I and II. The ultrasound underestimated the fecundity of shovelnose sturgeon by 5%. The ultrasound fecundity was lower than the true fecundity for stage III and during August. Using the endoscope, we viewed seven different egg color categories. Using a model selection procedure, the presence of four egg categories correctly predicted the reproductive stage ± one reproductive stage of shovelnose sturgeon 95% of the time. For pallid sturgeon, the ultrasound overestimated the density of eggs by 49% and the endoscope was able to view eggs in 50% of the pallid sturgeon. Individually, the ultrasound and endoscope can be used to assess certain reproductive characteristics in sturgeon. The use of both methods at the same time can be complementary depending on the parameter measured. These methods can be used to track gonad characteristics, including measuring Gonadosomatic Index in individuals and/or populations through time, which can be very useful when associating gonad characteristics with environmental spawning triggers or with repeated examinations of individual fish throughout the reproductive cycle.

TÉCNICA PARA MENSURAÇÃO OVARIANA POR VIDEOLAPAROSCOPIA EM AVES – MODELO EXPERIMENTAL – CODORNA-JAPONESA (Coturnix coturnix japonica)

“…Em peixes, a mensuração de ovos por ultrassonografia subestimou em 52% o tamanho dos mesmos (BRYAN et al, 2007).…”

Assessment of pallid sturgeon relative condition in the upper channelized Missouri River

“…Pallid sturgeons were classified as wild or hatchery-reared according to the presence of a hatchery mark and/or tag or by post hoc genetic determination DeHaan et al 2008). Gender and gonad maturation stage were determined using ultrasound and endoscopic techniques described in Bryan et al (2007) and Divers et al (2009) and fish categorized as reproductive (stage IV, ready to spawn this season) or non-reproductive (stage IIÀIII; Moos 1978; Colombo et al 2007;Tripp et al 2009). The number of eggs released was estimated using volumetric estimation by counting a subset of number of eggs/mL and extrapolating to the total volume extracted.…”

Gonad Ultrasonography Image Preprocessing for Mahseer (Tor Tombroides)

“…To our knowledge, the fish documented for now are sturgeon ( Chiotti et al, 2016;Petochi et al, 2011;Du et al, 2017;Colombo et al, 2011;Bryan et al, 2007), bass (Macri et al, 2013;Will et al, 2002;Jennings et al, 2005), salmon (Frost et al, 2014), catfish (Guitreau et al, 2012;Bryan et al, 2005; Achionye-Nzeh and Jimoh 2010), halibut (Protopapadakis et al, 2015;Loher and Stephens 2011), rainbow trout (Hliwa et al, 2014), hapuku (Kohn et al, 2013), shark (Whittamore et al, 2010;Daly et al, 2007), thornback ray (Whittamore et al, 2010), haddock (MartinRobichaud andBerlinsky, 2004), cod (McEvoy, 2009), however ultrasonography on Mahseer has never been documented.…”