The effects of broodstock density and season on the fecundity of the

Hirudinaria

manillensis

under experimental conditions was evaluated using single factor analysis of variance and other methods. The results showed that

during autumnwinter

the broodstock density could not influence the fertilization ratio

the mean number of cocoons produced and mortalities of broodstock leeches significantly (P

>

0.05). Hatching rates

mean hatching numbers of cocoons and the cocoon size and wet weight under different densities were significantly different (P

<

0.05)

and among the four density groups

the density of 50 ind·tank

-1

 were lower than other groups. In springsummer

the fertilization ratios

mean hatching numbers of cocoons and the standard diameters of the cocoons produced by the broodstock leeches were not significantly different among the four density groups (P

>

0.05). The number of cocoon laid by the broodstock leeches

hatching rates of cocoons

mortalities of broodstock leeches

the standard lengths and cocoon wet weights were significantly different among the different densities (P

<

0.05)

and the average number of cocoons laid and hatching rates of cocoons were the highest under the density of 5 ind·tank

-1

. Mortality under the density of 50 ind·tank

-1

 was the highest at 29.60±5.55 ％

which was higher than those of other groups markedly. Furthermore

the group with 50 ind·tank

-1

had the smallest cocoon length and wet weight. These results demonstrated that the reproductive indices of parent leeches were the best optimal at 5 ind·tank

-1

 density treatment in different seasons

and seasonal change significantly affects the reproductive efficiency of the leech

H.manillensis

at the same broodstock density. The reproductive efficiency of parent leeches in spring-summer was higher than that in autumnwinter significantly

especially the hatching period in springsummer (44 d) was fewer than that in autumnwinter (100 d). In conclusion

this investigation has obtained the optimal breeding density

and demonstrated that the possibility of multiple reproduction of parent leeches during a year in southern China. This new information on the effect of season and density is beneficial for the commercial rearing and breeding industry of this species.