| Bighead carp(Aristichthys nobilis) is one of the “four major Chinese carps†with rich nutritional value. This study comparatively analyzed the water quality, natural food organism population characteristic, morphological characteristics and flesh quality of bighead carp among groups from four treatments as fertilization(group A), fertilization+1/2 feeding(group B), fertilization+feeding(group C) and feeding(group D). The crude protein, crude fat, crude ash, moisture, p H, water holding capacity, contents of mineral elements, flavor amino acid were investigated to assess the flesh quality. Meanwhile, the cultured aquatic environmental factors were also compared to co-analyze the difference in morphological charactristics and flesh quality. The positive results provided theoretical basis for the sustainable and healthy bighead carp pond farming for Central China. The results are as follows:1.During the experiment, the ranges of the change in aquatic environmental factors fluctuated as follow, p H 7.03~8.93, SD 15~65 cm, WT 22.9~32.3℃,DO 0.36~17.38 mg/L, PO43--P 0.34~3.68 mg/L, TP 1.23~9.34 mg/L, TN 0.5~12.1 mg/L,NH+-N 0.01~3.56 mg/L, NO3--N 0.1~1.2mg/L,NO2--N 0.001~0.444mg/L. The main water quality parameters had no significant differences during the middle and later cultured period.2.During the experiment, 75 species of zooplankton in 52 genera were confirmed as, 34 species of Protozoa in 28 genera, 33 species of Rotifera in 17 genera, 6 species of Cladocera in 5 genera, 2 speices of Copepoda in 2 genera. The dominant species of zooplankton biomass of feeding groups is much higher than that of fertilization group. The biomass, density, biodiversity index of the zooplankton in fertilization groups were so low, leading to the insufficient of the nature food organism for bighead carp.3.The morphological variation of bighead carp(A. nobilis) feeding by feedstuff were investigated. The four groups of bighead carp differed significantly(P<0.05) in 26 morphological proportional characters(e.g., TL/BL, BH/BL, SL/BL), while there were no difference in other characters of HH/BL, HL/BL, 4-6/BL, 5-6/BL among different groups. The cluster analysis indicated that the group B, group C and group D were more similar compared to group A. The principal component analysis yielded seven principal components with a cumulative contribution ratio of 94.63%. The scatter diagram of major principle components also showed group A completely separated from the other three groups, while the latter overlapped together. The discriminant functions of the four populations of bighead carp were established based on 6 morphological characters that differed significantly among the populations. The accuracy of discrimination from four populations was 92.7%, 87.5%, 64.3% and 87.5%, respectively, indicating the reliability of discriminant functions. In summary, the morphological characteristics of bighead carp feeding feedstuff changed significantly. However, the morphological characters of fish head have not changed, while the trunk from head to the dorsal fin is significantly increased, in hence giving an illusion of smaller head. It is the first study to prove the bighead carp feeding feedstuff still meet the big head features people liking, laying the theoretical foundation for rearing bighead carp with feedstuff.4.In the aspects of growth and flesh quality. Bighead carp belonged to high-protein and low-fat fish. Feeding significantly increased the growth rate of bighead carp, compared to fertilization group, implying that feeding can improve the yield of bighead carp in pond farming. Interms of nutrient composition, crude protein and crude fat content in feeding group was significantly higher than that in fertilization group, while the water content was significantly in opposite. Fertilization group had high average p H, water holding capacity and rich mineral elements as the same characteristics in wild. The feeding group of bighead carp has better taste and higher nutritional value. In flesh quality of feeding group, glutamate had the highest content and cysteine revealed the lowest. The amino acid content tested in fertilization group was all lower than that in the other 3 groups(P<0.05), while there was no significant difference between the fertilization+1/2feeding group and fertilization+feeding group(P>0.05) except leucine content. The amount of four kinds delicious amino acids and EAAI in the fertilization+feeding group were the highest, while these of the fertilization group were the lowest(DW). 17 kinds of detected fatty acids content significantly different(P<0.05), except for C17:1, C18:3, C30:3 and saturated fatty acid.In summary, the results showed that the flesh quality and morphological messurable characteristics were mainly affected by feed. The fertilization+ feeding group can produce more high quality aquatic products, which may be a good farming mode. |
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