Abstract
To investigate the growth and feeding conditions of the Chinese mitten crab Eriocheir sinensis under different feeding modes: traditional (mainly consisting of wheat, bran, and soybean meal), formulated, and mixed feeds (1:1 mixture of traditional and formulated feeds) were fed in different crab breeding ponds in this study. During the experiment, the stomach contents of juvenile crabs under the different feeding modes were collected. The main potential eukaryotic food components were studied using 18S ribosomal DNA sequencing, and the contribution of different feeding modes to the feeding source of juvenile crabs were analyzed using C and N stable isotopes. The terminal weight and weight gain rate of crabs under the formulated feeding mode were significantly higher than those in the traditional and mixed feeding modes (P < 0.05). No differences were observed in the diversity and abundance of the main potential eukaryotic feed components of male and female crabs under different feeding modes (P > 0.05). Thirty-four phyla, composed mainly of benthic organisms, were identified, with Arthropoda (mainly including Malacostraca, 30.25–51.48%), Phragmoplastophyta (mainly including Embryophyta and Trebouxiophyceae, 5.08–24.74%), and Diatomea (3.13–8.43%) being the most abundant. The δ13C and δ15N values of the feeding sources and muscle of crabs ranged from −34.45 to −22.21‰, and from 0.27 to 5.66‰, respectively, varying greatly among the three feeding modes and δ15N value of muscle under formulated feeding mode was significantly higher than that in traditional feeding mode (P < 0.05). The proportion of particulate organic matter (11.92–17.50%) is similar to Alternanthera philoxeroides (11.24–16.03%) in three feeding modes. There was no significant difference in feeding habits between male and female crabs under the same and different feeding modes. Juvenile crabs feed on both plant- and animal-based feeds in an aquaculture pond, but they are not complete predators and selectively feed on animal or plant feeds as supplements of that which is deficient, in addition to their main feed.
Highlights
The Chinese mitten crab, Eriocheir sinensis, which belongs to the phylum Arthropoda, subphylum Crustacea, order Decapoda, and family Graspidae, is one of the major economically important farmed crab species in China (Huang et al, 2019)
At the end of the breeding stage (November), there was no significant difference in the average weight between the traditional feeding mode (8.43 ± 2.13) and the mixed feeding mode (8.36 ± 2.39) (P > 0.05), which was significantly lower than the average weight of the juvenile crabs in the formulated feeding mode (10.52 ± 2.60) (P < 0.05)
The results showed that the contents of Phragmoplastophyta in the stomach of male (23.20 ± 0.15%) and female (18.99 ± 0.16%) crabs was the highest under the formulated feeding mode, and the contents of Diatom in the stomach of male (8.43 ± 0.02%) and female (6.96 ± 0.02%) crabs was the highest under the mixed feeding mode, while the contents of Phragmoplastophyta and Diatom in the stomach of crabs were the lowest under the traditional feeding mode
Summary
The Chinese mitten crab, Eriocheir sinensis, which belongs to the phylum Arthropoda, subphylum Crustacea, order Decapoda, and family Graspidae, is one of the major economically important farmed crab species in China (Huang et al, 2019). The traditional feeding mode, which plays a leading role in the culture of juvenile E. sinensis in China, mainly contains soybean meal, bran, rapeseed meal and wheat (Wang and Wang, 2013; He et al, 2014). This feeding mode is cheaper, but will lead to problems such as early maturity of crab species, poor quality of adult crab and deterioration of water quality, which seriously restricts the green and sustainable development of the culture industry of E. sinensis (Pan et al, 2016). The food composition of E. sinensis under these different feeding modes and the contribution of the different feed sources to its growth have not been reported yet
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