| By analyzing the data of body weight, body length and carapace length in the whole culture process of M.japonicus, fitting the growth curve of morphological traits, assessing the growth characteristics and rules of M.japonicus, aim to provide theoretical basis and technical parameters for the actual breeding process. In the same time, use multivariate analysis to analyze the law of relative growth in body length, total length, carapace length, carapace height, carapace width, first Abdominal segment height, third Abdominal segment height , first Abdominal segment width, third Abdominal segment width, sixth abdominal segment length and weight with the growth of months. Aim to provide theoretical basis for the problems that may arise in M.japonicus breeding. Then through monitoring the type and quantity of plankton in M.japonicus ponds during the whole breeding, monitoring the diurnal vertical migration of plankton in the late breeding, aim to understand the composition and diversity of plankton community and the diurnal vertical migration of plankton.The results indicate that:The relationship of body length and weight could be described by the power function: W = 1.182×10-5L3.0235. Value b was close to 3. This means an isometric growth. There were three stages in its growth: Fast growth stage 30-60 days ,Steady growth stage 60-90 days and Aging growth stage 90 days later. The condition factor was gradually increased in a significant trend at early and middle growth stage(1.14-1.23),and later in a gradually decreased trend (1.19- 1.14).The von Bertallanffy equations were as follows: Lt=111.796[1-e-0.0123 (t+0.07654)] ,Wt=15.611[1-e-0.0123 (t+0.07654)] 3.0235. The inflection of body weight growth was about 89.9 days.Result shows that the correlation between any two traits of M.japonicus is significant at all tested ages. The correlation coefficient of body length and total length are the maximum among 1-3 months, the correlation coefficient of total length and carapace width are the maximum among 4 months, the correlation coefficient of body length and weight are the maximum among 5 months. The principal components of M.japonicus at diffenrent ages are different. The first principal component of M.japonicus at first month is length factor , from two month of age to three months is height factor, and from four month of age to five months is weight factor. The month age closely related to the size of M.japonicus which has missed the best growing period can be deduced by employing the discriminant equations mentioned in this paper and the results of the discriminant analysis demonstrate that the overall accuracy is 92.33 %.A total of 26 species of phytoplankton were identified in the 4 M.japonicus culture ponds belonging to 7 phyla. They included 5 Cyanophyta species, 7 Chlorophyta species, 7 Bacillariophyta species, 1 Euglenophyta species, 2 Cryptophyta species, 2 Pyrrophyta species. In the early and mid farming, Chlorophyta and Bacillariophyta were the dominant species, in the later farming, Cyanophyta, Chlorophyta and Bacillariophyta were the dominant species. Succession of the phytoplankton community was rapid in the pre-rearing period. There were 4 species of zoonplankton identified, which included 8 Protozoa, 3 Copepoda, 2 Rotatoria and 3 Others larvas. In the early farming, Protozoa, Copepoda and Rotatoria were the dominant species, in the mid farming, Protozoa and Rotatoria were the dominant species, in the later farming, Protozoa was the dominant species. Succession of the zoonplankton community was rapid in the pre-rearing period, and reached a peak in the mid-period, then fell in the last period. The biodiversity index of phytoplankton and zoonplankton were lower throughout the whole period, just only 1.19-1.30 and 0.25-0.72. But the habitat density trend of phytoplankton and zoonplankton were consistent, and showed linear relationship in quantity, the average of linear coefficient was R2=0.8553.In the late period, the diurnal variation of temperature and DO were significant (R<0.05), and pH was not significant(R>0.05), but the vertical variation of temperature, pH and DO in various time points were not significant. The vertical variation of nitrogen, phosphorus and COD in various time points were not significant(R>0.05), the diurnal variation of nitrogen and phosphorus were not significant(R>0.05), and COD was significant(R<0.05). The total number of phytoplankton in C were greater than B and A , and the distribution of diurnal vertical were similar in every regional, which were floating in the morning, sinking in the noon, then floating again at dusk, sinking in the midnight. Cryptophyta, Pyrrophyta and Cyanophyta were floating in the morning and sinking in the night. Chlorophyta were floating in the morning, sinking in the noon, then floating again at dusk, sinking in the midnight. The distribution of Bacillariophyta was uniform, and the distribution of diurnal vertical was not obvious. The diurnal vertical migration of tatal zoonplankton were not significant, but the diurnal vertical migration of Balanus larva and Copepoda were signifcant. Copepoda larva mainly stayed in the 30-120 cm water layer, Calanus, M.norvegica and Balanus larva were floating in the morning and sinking in the night, and Balanus larva migrated to the periphery from night. These may be related to the light intensity, the adaptability of M.japonicus′living habits and avoid predation. |
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