DEVELOPMENT OF A SYSTEMATIC APPROACH TO DIAGNOSTIC ULTRASOUND IN NILE TILAPIA Oreochromis niloticus

Ultrasound imaging uses high-frequency sound waves  (2 to  >  55 MHz) to visualize internal anatomy for diagnostic procedure s. Ultrasonography has been used in aquaculture and fisheries sinc e the early 1980s; however, its widespread use  and potential contribution is limited by high variability in equipment,  diverse fish morphology, and inadequate reporting of control settings used. The goal of this  study  was  to develop systematic  fish handling and ultrasound scanning procedures for viewing internal anatomy  and reproductive organs  in  Nile Tilapia. The objectives were to (1) assess fish handling and probe positioning procedures; (2) manipulate and evaluate pr imary ultrasound control settings (frequency, focus, depth, gain) at  three external anatomy landmarks; and, (3)  develop systematic, reliable, reproducible fish handling and ultrasound procedures .

Adult Nile Tilapia (24 females: 24 males) were scanned using  the  EVO II Ultrasound  Scanner (E.I Medical Imaging, CO) equipped with a  (6-14 MHz)  multiple-frequency range  waterproof probe in  lateral, ventral, and dorsal recumbence . Probe positioning  and settings were  developed on external anatomy landmarks (Figure 1). C ross-sectional  ultrasound  images  on the transverse plan (Figure 1-B), and  the  gross morphology of frozen fish  were recorded (Figure 1-C) . Fish positioning, probe placement at external landmarks,  control settings,  and  data obt ained from the frozen cross-section were used to  inform image interpretation and development of a systematic  ultrasonography  approach  to  generate new data for reproduction research on Nile Tilapia  and to create a diagnostic ultrasound user- guide for tilapia hatcheries.