Effects of temperature on the final stages of sexual maturation in Atlantic salmon (Salmo salar L.)
- 429 Downloads
Maturing male and female Atlantic salmon (Salmo salar L.) were held under three temperature regimes for 10 weeks between September and December: warm (constant 14–16 °C), ambient (decreasing from 11 to 5 °C), and cold (decreasing from 7 to 3 °C). Blood samples were analyzed for plasma steroid levels, and the fish were inspected for the presence of expressible milt (total volume and spermatocrit) and ovulation weekly. Samples of eggs were dry-fertilized with milt stripped from three males held at the same temperatures and incubated until the eyed stage. In females, levels of plasma testosterone (T) and 17β-oestradiol (E2) dropped as ovulation approached, concurrent with a rapid increase in levels of plasma 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P). In males, levels of T and 11-ketotestosterone (11-KT) peaked 2–3 weeks after the first appearance of expressible milt, while levels of 17,20β-P increased steadily and did not exhibit a definite peak. Exposure of females to cold water amplified and advanced the profiles of all three steroids compared with the ambient group, and increased the survival rates to the eyed egg stage. Cold water had no immediate effect on the male steroid profiles, but later, higher levels of 17,20β-P were evident compared with both the ambient controls and the warm water group, while the effects on 11-KT and T were more variable. Exposure to warm water completely inhibited both milt production and ovulation. Moreover, warm water modulated the steroid profiles of the males with lower 11-KT levels compared with ambient controls and lower 17,20β-P level compared with cold-water-treated males. In females, warm water resulted in total inhibition of the peri-ovulatory peak in 17,20β-P and prevented the normal decline of T and E2 levels associated with ovulation. The findings of the present study are highly relevant for broodstock management in aquaculture, as well in understanding the impact of climate change/temperature variability on wild salmon spawning.
KeywordsAtlantic salmon Temperature Spawning Milt production Spermiation Ovulation Phase advance Plasma steroids
The authors would like to thank the staff at the Institute of Marine Research, Matre, for their valuable assistance in the preparation and execution of the experimental work and subsequent analyses. Ms. Sissel Waage Kalvenes and Ms. Svanhild Lohne Gokstad at the Institute of Marine Research, Austevoll, are acknowledged for skillful assistance with steroid ELISAs. This study was financed by the Norwegian Research Council Grant No. 133937/122.
- Chan STH, Yeung WSB (1986) A new method for the simultaneous determination of androstenedione, testosterone, 11-oxotestosterone and 11-β-OH-testosterone in fish plasma using combined techniques of celite chromatography and radioimmunoassay. J Steroid Biochem Mol Biol 25:1013–1021CrossRefGoogle Scholar
- Fostier A, LeGac F, Loir M (1987) Steroids in male reproduction. In: Idler DR, Crim LW, Walsh JM (eds) Proceedings of the third international symposium on the reproductive physiology of fish, St. John’s, Newfoundland, pp 239–241Google Scholar
- King HR, Pankhurst NW (2000) Ovulation of Tasmanian Atlantic salmon maintained at elevated temperatures: implications of climate change for sustainable industry development. In: Norberg B, Kjesbu OS, Taranger GL, Andersson E, Stefansson SO (eds) Proceedings of the 6th international symposium on the reproductive physiology of fish, Bergen, pp 396–398Google Scholar
- Mayer I, Berglund I, Rydevik M, Borg B, Schulz R (1990a) Plasma levels of five androgens and 17α-hydroxy-20β-dihydroprogesterone in immature and mature male Baltic salmon (Salmo salar) parr, and the effects of castration and androgen-replacement in mature parr. Can J Zool Rev Can Zool 68:263–267CrossRefGoogle Scholar
- Mayer I, Lundqvist H, Berglund I, Schmitz M, Schulz R, Borg B (1990b) Seasonal endocrine changes in Baltic salmon, Salmo salar, immature parr and mature male parr 1. Plasma-levels of 5 androgens, 17α-hydroxy-20β-dihydroprogesterone, and 17β-estradiol. Can J Zool Rev Can Zool 68:1360–1365CrossRefGoogle Scholar
- Pavlidis M, Dimitriou D, Dessypris A (1994) Testosterone and 17β-estradiol plasma fluctuations throughout spawning period in male and female rainbow trout Oncorhynchus mykiss (Walbaum), kept under several photoperiod regimes. Ann Zool Fenn 31:319–327Google Scholar
- Rodriguez L, Begtashi I, Zanuy S, Carillo M (2000) Development and validation of an enzyme immunoassay for testosterone: effects of photoperiod on plasma testosterone levels and gonadal development in male sea bass (Dicentrachus labrax L.) at puberty. Fish Physiol Biochem 23:141–150CrossRefGoogle Scholar
- Scott AP, Liley NR (1994) Dynamics of excretion of 17,20β-dihydroxypregn-4-en-3-one 20-sulphate, and of the glucuronides of testosterone and 17β-oestradiol, by urine of reproductively mature male and female rainbow trout (Oncorhynchus mykiss). J Fish Biol 44:117–129Google Scholar
- Taranger GL, Hansen T (1993) Ovulation and egg survival following exposure of Atlantic salmon, Salmo salar L., broodstock to different water temperatures. Aquac Fish Manag 24:151–156Google Scholar
- Taranger GL, Stefansson SO, Oppedal F, Andersson E, Hansen T, Norberg B (2000) Photoperiod and temperature affect spawning time in Atlantic salmon (Salmo salar L.). In: Norberg B, Kjesbu OS, Taranger GL, Andersson E, Stefansson SO (eds) Proceedings of the 6th international symposium on the reproductive physiology of fish, Bergen, p 345Google Scholar