Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Using skin mucus for the identification of ovulation biomarkers in North American Atlantic salmon (Salmo salar)



Tracey Schock, Ashley Boggs-Russell, Erin Legacki, Brian Peterson, Heather Hamlin, Melissa Milligan


In Maine, North American Atlantic salmon production has experienced a 20% decrease in the eye-up rate of embryos. The maternal endocrine environment is suggested to be an important factor for ovulation and viable embryos but needs to be further investigated. Combining new matrices (skin mucus) and advanced technologies (liquid chromatography tandem mass spectrometry (LC-MS/MS)) will advance the knowledge of the endocrine status in reproductively mature North American Atlantic salmon. The objectives of this study were to 1) identify mucus as a viable matrix to measure steroid hormones, 2) quantify steroid hormone profile of North American Atlantic salmon during ovulation and 3) compare hormone profiles of salmon with high and low eye-up rates. Mucus and plasma were collected from sexually mature female North American Atlantic salmon (n= 29). Females were sampled before ovulation (n= 9) and after ovulation (n= 20) then analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Fish collected after ovulation were slotted into groups based on eye-up rate, fish with ≥ 70% eye-up rate (High eye-up, n=4) and fish with ≤ 70% eye up rate (Low eye-up, n=14). In mucus allopregnanolone, 11-deoxycorticosterone and 11-deoxycortisol were significantly higher after ovulation (p ≤ 0.05). Comparatively, in plasma allopregnanolone was significantly lower after ovulation and 17α, 20β-hydroxyprogesterone was significantly elevated after ovulation (p ≤ 0.05). Fish with a low eye-up rate had elevated mucus concentrations of corticosterone (p ≤ 0.05). While fish with a high eye-up rate had elevated plasma testosterone concentrations (p ≤ 0.05). Circulating androstenedione (R2= 0.46, p ≤ 0.05) and testosterone (R2= 0.47, p ≤ 0.05) were significantly correlated with eye-up rate. Mucosal concentrations of steroid hormone correlated with circulating concentrations of related steroids, and they reflected changes in reproductive physiology. The significant changes in mucosal and circulating steroid concentrations of the 5α reduced pregnane, allopregnanolone suggests a role of 5α-reduced pregnanes during ovulation in North American Atlantic salmon. To our knowledge this is the first time any 5α-reduced pregnane has been reported in teleosts. Mucosal concentrations of precursor glucocorticoids significantly elevated after ovulation combined with significant correlation with hydroxylated pregnanes suggests a synergistic mechanism between glucocorticoids and pregnanes is needed for ovulation. Additionally, glucocorticoids and androgens appear to influence the viability of fertilized eggs highlighting the need for further research into the synergistic role's hormones play in both oocyte maturation and embryo viability.


Atlantic salmon, LC-MS/MS, endocrine, ovulation, eye-up


Schock, T. , Boggs-Russell, A. , Legacki, E. , Peterson, B. , Hamlin, H. and Milligan, M. (2023), Using skin mucus for the identification of ovulation biomarkers in North American Atlantic salmon (Salmo salar), Aquaculture, [online],, (Accessed May 21, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created June 4, 2023, Updated August 18, 2023