Effects of GnRHa treatment during vitellogenesis on the reproductive physiology of thermally challenged female Atlantic salmon ( Salmo salar )

• Published in: PeerJ
• Main Authors: Anderson, K, Pankhurst, N, King, H, Elizur, A
• Format: Article in Journal/Newspaper
• Language: English
• Published: PeerJ, Ltd. 2017
• Subjects: Agricultural and Veterinary Sciences; Fisheries Sciences; Aquaculture; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.7717/peerj.3898; http://ecite.utas.edu.au/127614

Tasmanian Atlantic salmon ( S. salar ) broodstock can experience temperatures above 20C, which impairs reproductive development and inhibits ovulation. The present study investigated the prolonged use of gonadotropin releasing hormone analogue (GnRHa) during vitellogenesis as a means of maintaining endocrine function and promoting egg quality at elevated temperature in maiden and repeat spawning S. salar . GnRHa-treatment during vitellogenesis did not compensate for the negative effects of thermal challenge on the timing of ovulation, egg size, egg fertility or embryo survival in any fish maintained at 22C relative to 14C. The lack of effectiveness was reflected by the endocrine data, as plasma follicle stimulating hormone and luteinising hormone levels were not different between treated and untreated groups at 22C. Furthermore, plasma testosterone and E2 levels were unchanged in GnRHa-treated fish at 22C, and plasma levels were generally lower in both groups maintained at 22C relative to 14C. Transcription of vitellogenin, and zona pellucida B and C was not enhanced in GnRHa-treated fish relative to untreated fish at 22C, presumably due to observed suppression of plasma E2. These results indicate that thermal impairment of reproduction is likely to occur on multiple levels, and is difficult to overcome via hormonal manipulation.