A Review of the Use of Ultrasonography in Fish Reproduction

Abstract

Ultrasound imaging analysis involves development of an effective combination of physical properties, equipment, instrument settings, and protocols. This review focuses on the application of ultrasonography to fish reproduction. The goal was to assemble a comprehensive reference data set to serve as a decision‐enabling tool for potential users. The specific objectives were to (1) identify the ultrasound equipment, settings, and procedures used during examination, (2) review the fish handling procedures used during examination, and (3) review current data on sex identification and reproduction indices developed using ultrasonography. The 27 studies selected for inclusion in this review represent 21 fish species. Most (96%) of the studies reported the model name for the ultrasound unit, but only 19% reported the probe model. The most reported probe features were the frequency capability (96% of the studies) and array format (linear, sector, or annular; 81%). The majority of the studies (89%) did not report any of the control settings used. The combinations of handling and ultrasound procedures were variable even within the same species, and the majority (78%) of the studies included a form of restraint. None of the studies simultaneously integrated the use of unrestrained, unanesthetized, submersed fish with a submersed waterproof probe, which would enable the use of water as a transmission medium for ultrasound. Size, life stage, gonadal growth of reproductively active adults, and fish morphology influenced the ability to use ultrasonography for sex identification and the development and application of qualitative and quantitative reproductive indices. The utility of ultrasonography in fish reproduction has been repeatedly validated, and innovative indices for noninvasive use have been developed. However, this review identifies a clear lack of consistency in reporting of instrument settings and handling procedures and provides suggestions for standardizing the use of ultrasonography with aquatic species.

Use of Ultrasonography in Wildlife Species

“…For large fish, transducers of 2 to 5 megahertz (MHz) are usually chosen, and for small fish, 7.5 to 16 MHz would be more appropriate for better visualization of the small body structures. 55 This has been done in a wide range of fish species such as Coho salmon (Oncorhynchus kisutch), cod (Gadus morhua), Atlantic salmon (Salmo salar), and Pacific herring (Clupea harengus pallasi). In many of these species, conducting the examination from the ventral surface may produce better results.…”

A quality assurance initiative for commercial-scale production in high-throughput cryopreservation of blue catfish sperm

“…Specification design regulates the acceptance of materials with certain quality characteristics, so that waste and high variation in the process due to less-functional or non-functional components can be avoided [8]. For example, if the quality characteristics were defined by observable body features during selection and hormone injection of females for artificial spawning [12], the specification would be a flat belly (indicating poor potential for spawning); if the quality characteristic is the ultrasonic image features of gonads [24], the specification would be the absence of visible mature eggs. These specifications could help ensure that the final products would meet the basic expectation of farmers (customers).…”

Sperm Cryopreservation in Live-Bearing Xiphophorus Fishes: Offspring Production from Xiphophorus variatus and Strategies for Establishment of Sperm Repositories

“…Ultrasound is a noninvasive technique used for years in monitoring of fetal development in human medicine, and in recent years it has been used with large-bodied aquaculture fishes to identify ovarian developmental stages. 40 Thus far, the smallest fish for which conventional ultrasound has been used was the Neosho madtom Noturus placidus with 10 to 12 cm body length. 41 It is unknown if ultrasound techniques can be used with smaller fishes.…”