Aquaculture America 2023

February 23 - 26, 2023

New Orleans, Louisiana USA


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

National Cold Water Marine Aquaculture Center,

Franklin, ME, USA 04469


In Maine, North American (NA) Atlantic salmon production has experienced a 20% decrease in the eye-up rate of embryos and the maternal endocrine environment is suggested to be an important factor for fertilized eggs to eye-up. Historically, plasma sample collection and indirect hormonal measurement through immunoassays has made it difficult to complete endocrine pathways in NA Atlantic salmon.  Combining new matrices (skin mucus) and advanced technologies (liquid chromatography tandem mass spectrometry (LC-MS/MS)) reduces these historic complications. Mucus was collected from sexually mature NA Atlantic salmon through absorption onto filter paper. Females were sampled pre ovulation (n= 9) and post ovulation (n= 20). Samples from post-ovulatory fish were subdivided into fish with > 70% eye-up rate, n=4 and fish with ≤ 70% eye up rate, (n=14) after analysis. All samples were subjected to a methanol protein precipitation and analyzed with an LC-MS/MS method. The objectives of this study were to 1) identify mucus as a viable matrix to measure steroid hormones, 2) quantify steroid hormone profiles at pre- and post-ovulation of North American Atlantic salmon and 3) compare hormone profiles of salmon with high and low eye-up rates.

Pre-ovulation there was an inverse correlation between plasma pregnenolone and mucosal cortisol (r2 = -0.747, p ≤ 0.05) and mucosal 17,20 OHP (r2 = -0.8314, p ≤ 0.01). Post-ovulation, there was a significant correlation between circulating plasma pregnenolone and mucosal cortisone (r2 = 0.6037, p ≤ 0.01), mucosal cortisol (r2 = 0.623, p ≤ 0.01) and mucosal 5αDHT (r2 = 0.8862, p ≤ 0.01). Mucosal allopregnanolone, 11-deoxycorticosterone and 11-deoxycortisol were significantly higher post-ovulation (p ≤ 0.05). Fish with an eye-up rate ≤ 70% had elevated mucus concentrations of corticosterone (p ≤ 0.05).

Mucosal concentrations of glucocorticoids significantly elevated post-ovulation combined with significant correlation with hydroxylated pregnanes suggests a synergistic mechanism between glucocorticoids and pregnanes. This combined with the higher corticosterone concentrations in fish with lower eye-up rates suggest a more important role for glucocorticoids then previously suggested.