Validation of Endoscopy for Determination of Maturity in Small Salmonids and Sex of Mature Individuals

Abstract Fish maturity status, sex ratio, and age and size at first maturity are important parameters in population assessments and life history studies. In most empirical studies of these variables, fish are sacrificed and dissected to obtain data. However, maturity status and the sex of mature individuals can be determined by inserting an endoscope through a small incision in the body cavity wall and viewing the gonads. The objective of this study was to evaluate endoscopy in a field setting for gonadal assessment of stream-resident forms of salmonids that mature at small sizes. Ninety-one brook trout Salvelinus fontinalis (60–210 mm fork length [FL]) were obtained via electrofishing and anesthetized. Maturity status and sex of mature individuals were determined with an endoscope. After recovery, individuals were euthanized with anesthetic and were dissected to validate the endoscopic classification. Endoscopy correctly determined the maturity status and sex of mature individuals for 96% of the brook tr...