Ultrasound as a noninvasive tool for monitoring reproductive physiology in female Atlantic salmon (Salmo salar).

Ingun Naeve,Maren Mommens,Elin Kjørsvik,Augustine Arukwe

doi:10.14814/phy2.13640

Abstract

Aiming to explore ultrasound technology as a noninvasive method for maturation monitoring, we compared ultrasound observations and measurements in female Atlantic salmon (Salmo salar) during the last year before ovulation with standard, invasive methods such as gonadosomatic index (GSI), gonad histology and sex hormone analysis. Ultrasound measurements of ovaries correlated strongly (R > 0.9, P < 0.01) with ovary weight and GSI, and could be used as a noninvasive tool for GSI estimation. Using ultrasound, we were able to identify females with advanced oocyte development and elevated sex hormone and GSI levels earlier than previously observed. Histological studies confirmed these observations showing oocyte yolk accumulation 10 months before ovulation and 8 months before significant increase in sex hormones. Levels of the sex hormone 11‐keto testosterone (11‐KT) indicated a new role of this hormone at final maturation in salmon females. We propose the use of ultrasound as an alternative method to traditionally used invasive methods during sexual maturation monitoring in wild and farmed Atlantic salmon broodstock populations. Eliminating sacrifice of valuable broodfish, and reducing handling stress, would improve animal welfare in present‐day broodstock management.

Highlights

Salmonid species are of great economic and nutritional value, and as a consequence their reproduction has been thoroughly studied over decades (Ducharme 1969; Bun Ng and Idler 1978)
In studies covering different aspects of salmonid reproduction, gonadosomatic index (GSI) is typically reported in combination with one or more other methods of maturation index, such as sex hormone analysis (Nagahama and Adachi 1985; Prat et al 1996; Taranger et al 1998; King and Pankhurst 2003), histology of gonad tissues (Sumpter et al 1984; Taranger et al 1999; Estay et al 2003; Grier et al 2007), endoscopy (Ortenburger et al 1996; Swenson et al 2007) and expression of genes related to sexual maturation in relevant tissues (Campbell et al 2006; Luckenbach et al 2008)
There was a strong correlation between left ovary length and total ovary weight (R = 0.94, P < 0.01, Fig. 1A), and left ovary length measured by ultrasound correlated well with real left ovary length (R = 0.99, P < 0.01, Fig. 1B)

Summary

Introduction

Salmonid species are of great economic and nutritional value, and as a consequence their reproduction has been thoroughly studied over decades (Ducharme 1969; Bun Ng and Idler 1978). In studies covering different aspects of salmonid reproduction, GSI is typically reported in combination with one or more other methods of maturation index, such as sex hormone analysis (Nagahama and Adachi 1985; Prat et al 1996; Taranger et al 1998; King and Pankhurst 2003), histology of gonad tissues (Sumpter et al 1984; Taranger et al 1999; Estay et al 2003; Grier et al 2007), endoscopy (Ortenburger et al 1996; Swenson et al 2007) and expression of genes related to sexual maturation in relevant tissues (Campbell et al 2006; Luckenbach et al 2008)

Objectives

Methods

Results

Conclusion