ECOLOGICAL STUDY ON REPRODUCTION AND GROWTH OF PLANKTONIC COPEPOD Calanus Sinicus

The effect of the environmental factors such as temperature and food on reproduction and growth of planktonic copepod Ca/anus sinicus, the key species in the Yellow Sea and Eeast China Sea, was studied in the laboratory. Results of these experiments show that 1) The pattern of egg-laying of Ca/anus sinicus is in a discrete way, and the duration of spawning and non-spawning period is different between individuals. The duration of spawning is ranged from 1 to 9 days, and the longest one is 9 days; the non-spawning period varied from I to 6 days, generally 1? days. 2) Females have 3 days response to food changes in egg production. No eggs were produced after the females starved 6 days, and they resumed egg production after they were fed again. Starvation decreased the fecundity of the female, and the quality of the food has a strong influence on the egg production. 3) The speed of hatching slowed with the decreasing temperature. There is no more eggs hatched after 25h at 18.7C, 43.5h at 16.04, and 93.4h at 7C, respectively; and few eggs hatched at 3.7 .C. 4) According to the obtained experimental results, the duration of NI~ NI! extended with the decrease of temperature, the durations from eggs to NIh are about 8-9 days, 6-7 days, 4.5 days at 7.FC, 9.1, 15.4C respectively. 5) The durations of the Nauplii and Copepodite fed on Skeletonema costatu are pronouncedly shorter than those fed on Phaeodaciylum tricornutum, especially the durations of NI!! and NIV. The generation time of the Ca/anus sinicus fed on Skeletonema costatu is about 27 days. In the experiment we found that the duration of NI or Nil is very short, that of NIII or NIV is much longer, only those of NV-Cl! seems to be isochronal, and the later stages returned to relatively longer durations again, so we conclude the whole larval stage of C.sinicus doesn follow the sochronal?rule. When using S. Costatu as food, the duration of CIII is the longest. 6) The mean growth rate of each stage increased with the stage development, but the growth rate of each stage is not always the same owing to food quality. From June 2000 to May 2001, egg production rate and hatching rate were determined in the field. The results show that the mean egg production rate of C.sinicus integrated for all stations is high in spring, intermediate in summer, and low in winter, and get its minimum value in autumn. The hatching rate ranged from 75% to 100%, which indicated that the mating conduct of this species is very successful, and that food condition is good.