This study was conducted to investigate the effects of two carotenoids (astaxanthin and
b-carotene) on the sperm quality of goldfish Carassius auratus (Linnaeus, 1758). For this
purpose, six diets containing concentrations of 50, 100, and 150 mg/kg of synthetic astaxanthin
and b-carotene were added to a basic carp diet. One group of fish was also fed with a
control diet (no added carotenoids). Osmolality, spermatocrit value, and sperm concentration
significantly increased in the treatment supplemented with 150 mg/kg of astaxanthin
(296.6 1.1 mOsm/kg; 29.2 0.6%; 17.2 0.4 109 cells/mL, respectively) and
b-carotene (295.2 2.1 mOsm/kg; 32.5 1.6%; 17.9 0.5 109 cells/mL, respectively). The
highest concentration of astaxanthin (10.4 1.4 mg/kg) was recorded in the treatment of
A150 (P < 0.05) and did not differ between b-carotene treatments. The highest motility was
observed in the A150 and B150 treatments, and the lowest was observed in the control group
(P < 0.05). The artificial fertilization of the treated males with the similar females (fed with
the control diet) showed that the fertilization rate in the A150 treatments was higher than in
the other treatments (P < 0.05). In conclusion, dietary supplementation with 150 mg/kg of
astaxanthin improves osmolality, motility, fertilization rate, and sperm concentration.