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This study determined the effect of human chorionic gonadotropin (hCG) and handling stress on the spermiation and milt response of silver perch Leiopotherapon plumbeus based on the measurement of spermatocrit, sperm density, and milt production. Compared to saline-injected fish, the mean spermatocrit (or packed sperm) of hCG-treated fish was significantly lower at 18 h (47.9%) and 30 h (40.2%) post-injection while mean sperm density was significantly lower at 30 h post-injection (3.6 9 10 6 cells ll À1 ) but not at 18 h. At 18 h (1.8 ll g-BW À1 ) and 30 h (2.5 ll g-BW À1 ) post-injection, mean milt production of hCG-treated fish was significantly higher than in the saline group. Milt consistency was also thinner in the hCG-treated group. Mean sperm density of handled fish (18.0 9 10 6 cells ll À1 ) was significantly lower than control fish (23.4 9 10 6 cells ll À1 ). However, mean sperm density of handled plus saline-injected (16.2 9 10 6 cells ll À1 ) and handled plus hCG-treated fish (8.4 9 10 6 cells ll À1 ) was significantly lower than in the control goup. Having thicker milt consistency, mean spermatocrit and milt production of handled (77.5%; 1.1 ll g-BW À1 , respectively) and handled plus saline-injected fish (75.4%; 1.1 ll g-BW À1 , respectively) were not significantly different from the control fish (76.2%; 1.3 ll g-BW À1 , respectively). Handled plus hCG-treated fish had the lowest mean sperm density (8.4 9 10 6 cells ll À1 ) and spermatocrit (54.7%), but had the highest mean milt production (5.5 ll g-BW À1 ) among the treatment groups. These results demonstrate that the hCG injection effectively induces spermiation and milt expression and that handling-related stress negatively affects such responses. The spermatocrit method may be used to assess the spermiation and milt response of silver perch. U.S.

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