Efficacy of a high- and low-frequency ultrasonic probe for measuring ovary volume and estimating fecundity of striped bass Morone saxatilis in the Savannah River Estuary

Over the past few decades, ultrasonography has been used intermittently as a non-invasive, diagnostic tool for evaluating a variety of conditions in aquatic organisms. There has been a recent upsurge in scientific articles in which ultrasound images were used as a diagnostic tool, and the predominant use was to evaluate gender and other reproductive issues. Ultrasonography equipment is available in a variety of configurations, but we are unaware of any published literature that evaluates the efficacy of the various probe types for diverse uses (e.g., anatomical and physiological examinations). In this paper, we compare striped bass ovary volume and fecundity data based on ultrasonic images produced by probes with different frequencies and array types and offer considerations for determining which frequency or array type best facilitates various potential applications. Both the 3.5/5.0 MHz and the 6.0/8.0 MHz probes were equally effective in determining striped bass sex, but not for determining ovary volume. The 3.5/5.0 MHz curved array probe offered the best resolution of female striped bass ovaries. However, ovary area measurements had to be performed in the field because the curved images were incompatible with the image analysis software used in the lab. The 6.0/8.0 MHz linear array probe provided only partial images of ovaries in striped bass > 850 mm, and estimates of ovary area were based on several scanned and recorded images. However, the 6.0/8.0 MHz linear array probe has the advantage of a field scan, which can be recorded and later calibrated to computer image analysis software in the lab. Careful consideration of the type of animal and parts of its anatomy to be imaged as well as the image acquisition and processing circumstances should be undertaken to ensure that the ultrasonic imaging technology used is appropriate to the task.