Effect of elevated summer temperatures on gonadal steroid production, vitellogenesis and egg quality in female Atlantic salmon

Abstract

Groups of Tasmanian female Atlantic salmon Salmo salar L. were maintained at 14, 18 and 22° C for 3 months from mid‐summer (January). Blood plasma levels of 17β‐oestradiol (E2), testosterone (T), cortisol and vitellogenin (Vtg) were measured at regular intervals, and in autumn (April) temperatures were reduced to 8° C to facilitate spawning and egg incubation. Maintenance at 22° C during vitellogenesis was associated with a general reduction in plasma E2 levels and an early reduction in plasma Vtg levels relative to those observed in fish held at 14 and 18° C. Significantly reduced oocyte diameters in ova from fish held at 22° C (5·4 mm cf. 5·7 mm) confirmed reduced maternal investment, and an increase in the incidence of previously undescribed chorion damage suggested that zonagenesis may also have been impaired. As a result, the fertility and survival of ova from fish exposed to 22° C (69 and 42%, respectively) were significantly reduced relative to those of ova from fish maintained at 14° C (93 and 86%) and 18° C (86 and 84%).

Effects of Water Temperature on Gonad Development in the Cold-Water Fish, Kumgang Fat Minnow <i>Rhynchocypris kumgangensis</i>

“…HSI has been shown to be affected by the levels of various hormones, including E2 and insulin-like growth factor-1 (IGF-1). Since E2 treatment has been found to increase HSI and vitellogenin synthesis in numerous fish species (Osachoff et al 2013, Pandelides et al 2014, Park et al 2010) and elevated water temperatures impair E2 secretion (King et al 2003), we speculate that the elevated water temperature might have attenuated E2 secretion in our system, leading to the observed reductions in HSI. Long-term exposure to warm temperatures was previously shown to decrease IGF-1 levels, HSI values, and growth among juveniles of the southern flounder, Paralichthys lethostigma (Luckenbach et al 2007).…”

“…For example, exposure to high or low water temperatures was shown to attenuate gonadal maturation in both sexes of the pike-perch, Sander lucioperca (Hermelink et al 2011). High water temperatures reportedly damaged oocyte surfaces and reduced oocyte size via decreased levels of plasma gonadal hormone in the salmon, Salmo salar (King et al 2003). In the pejerrey, Odontesthes bonariensis, elevated temperatures reduced hormone levels in the brainpituitary-gonad axis, leading to gonadal regression and impaired spawning (Miranda et al 2013).…”

“…Almost all temperate fish undergo annual growth in the summer, when the food availability is good and the water temperature is optimal for growth (Ficke et al 2007). However, elevated water temperatures may interrupt the completion of vitellogenesis and gonadal development, affect egg quality and survival, cause defects in final maturation, inhibit ovulation (King et al 2003, Pankhurst et al 1996, and disrupt the release of reproductive hormones (Miranda et al 2013, Pankhurst andKing 2010).…”

Effects of elevated water temperature and food availability on the reproductive performance of a coral reef fish

“…However, the observed reduction in egg size suggests that exposure to elevated temperatures did have an effect on vitellogenesis in the present study. Reductions in final egg size in thermally stressed fish have been reported in rainbow trout (Pankhurst & Thomas 1998) and Atlantic salmon Salmo salar (King et al 2003). This was associated with reductions in plasma E 2 levels, and levels of the yolk precursor vitellogenin (in turn synthesized by the liver in response to stimulation by E 2 ) in Atlantic salmon, but no change in plasma E 2 in rainbow trout (Pankhurst et al 1996, Pankhurst & Thomas 1998.…”

Identification of follicular vitellogenesis stage by monitoring of plasma calcium and estradiol-17β concentrations in the cultured Caspian brown trout, Salmo trutta caspius Kessler, 1877

“…Results showed that cortisol (as most physiological response to stress) reduces the Vtg protein levels without affecting the Vtg mRNA levels. King et al (2003) showed that temperature stress has adverse impact on follicular vitellogenesis of Atlantic salmon, Salmo salar L., 1758. In this regard, Maintenance at 22…”