Effect of maintenance at elevated temperatures on ovulation and luteinizing hormone releasing hormone analogue responsiveness of female Atlantic salmon ( Salmo salar) in Tasmania

• Published in: Aquaculture Vol. 233; no. 1; pp. 583 - 597
• Main Authors: King, H.R, Pankhurst, N.W
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 26-04-2004; Elsevier Science; Elsevier Sequoia S.A
• Subjects: Animal aquaculture; Animal productions; Atlantic salmon; Biological and medical sciences; Effects; Females; Fish; Fundamental and applied biological sciences. Psychology; Hormones; LHRHa; Ovulation; Pisciculture; Salmo salar; Steroids; Temperature; Vertebrate aquaculture; Australia; Tasmania; Oceania; Tasmania Australia; PSE, Australia, Tasmania; Temperature; Atlantic salmon; Ovulation; Steroids; LHRHa; Hormone; Vertebrata; Adenohypophyseal hormone; Pisces; Salmo salar; Luteinizing hormone; Female; Gonadotropin; Aquaculture
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2003.09.049

To examine the effect of maintenance at elevated water temperatures on the responsiveness of female Atlantic salmon (
Salmo salar) to luteinizing hormone releasing hormone analogues (LHRHa), sexually maturing 2-year-old female Atlantic salmon were maintained at water temperatures of 6, 11 or 16 °C from late in vitellogenesis (early April in Tasmania) throughout the periovulatory period (late April to early June). In early May, fish were treated with LHRHa (25 μg kg
−1 body weight) by injection or in a cholesterol pellet. Controls received saline injections and blank pellets. Fish were anaesthetised and blood sampled at treatment, and at 48-h intervals for up to 8 days post injection. Thereafter, regular ovulation checks were conducted until the end of the experiment. Plasma levels of the gonadal steroids testosterone (T), 17β-estradiol (E
2) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured and egg fertility and survival to the eyed stage were assessed. In controls, maintenance at 11 °C delayed ovulation relative to fish held at 6 °C whereas, in fish held at 16 °C, ovulation was inhibited until holding temperature was reduced to 8 °C on day 35 post injection. Treatment with LHRHa advanced ovulation in fish held at both 6 and 11 °C but had no effect on ovulation in fish held at 16 °C. Elevated plasma 17,20βP in controls was only evident in those fish held at 6 °C (>100 ng ml
−1), whereas LHRHa treatment was associated with high 17,20βP levels in fish held at both 6 and 11 °C (>60 ng ml
−1). In contrast, there was little production of 17,20βP in fish held at 16 °C irrespective of treatment (<25 ng ml
−1). In controls, prior maintenance at 16 °C was associated with significant reductions in the fertility and survival of ova (84.0% and 17.3%, respectively) relative to 6 °C (97.9% and 75.6%, respectively) and 11 °C (95.3% and 44.4%, respectively). The fertility and survival of ova from LHRHa-treated fish held at 6 and 11 °C did not differ significantly from that of controls but LHRHa-treated fish held at 16 °C either produced nonviable ova or died prior to ovulation. These observations indicate endocrine dysfunction and confirm a lack of maturational competence in Atlantic salmon maintained at elevated temperatures, and suggest that both impaired pituitary responsiveness and limited 20β-HSD activity may contribute to the observed lack of 17,20βP production in fish held at 16 °C.