Japanese eels Anguilla japonica, after cultured in fresh-water ponds forthree years, were stocked in fresh-water or salt-water ponds for one more year.During the last year, eels were sampled monthly from each pond to check and
analyze their maturity value. The sex percentages of eels were 75.00% of females and 22.22% of males(3.38:1), 2.78% couldn't be differentiated. Eels with body length of 70 to 79 cmor body weight of more than 800 g were mostly female. Those with body length of50 to 59 cm or body weight of 300 to 399 g were mostly male.
The condition factor of female eels stocked in salt-water pond was withpositive correlation to water temperature (p<0.05), while those stocked infresh-water ponds showed no correlation (p>0.05). The GSI of female eels,whether stocked in fresh-water or salt-water pond, was with negative correlationto water temperature (p<0.05).
In December, female eels stocked in salt-water pond with low watertemperature had the highest average value of GSI (1.65±0.60). The average GSIwas lowest (0.70±0.10) in August with high temperature.
Female eels stocked in salt-water pond were sampled (40 for each group) andinjected with the same quantity of hormones from October or November,respectively, to induce maturity. The results showed that body weight of bothgroups could increase to 120% initial weight. Yet injection times needed forfemale eels induced from November was less than that from October, demonstratedthat gonads of female eels in November developed further than in October.