Impacts of three feeding modes on the diet composition and contribution ratios for juvenile Chinese mitten crab Eriocheir sinensis

Abstract

The diet composition and contribution ratios for juvenile Chinese mitten crab Eriocheir sinensis can vary with different feeding modes during pond culturing. To investigate this, the stomach contents of juvenile crabs and the contributions of different food sources to their growth were compared across three feeding modes: alligator weed Alternanthera philoxeroides alone (Diet 1), formulated diet feed alone (Diet 2), and a 1:1 mixture of A. philoxeroides and the formulated diet (Diet 3). The analysis utilized 18 S rDNA high-throughput sequencing and carbon and nitrogen stable isotopes. There were five replicates for each treatment group, and the experimental period was 120 d. The results showed that the diversity of the food composition in the stomach contents of the juvenile crabs was significantly lower (P < 0.05) with Diet 2 than with Diets 1 and 3. The seven phyla with the highest relative abundances in the stomach contents in descending order were Chloroplastida; Stramenopiles, Alveolata, and Rhizaria (SAR); Arthropoda; Cryptomycota; Phragmoplastophyta; Rotifera; and Eukaryota. The highest abundance of Phragmoplastophyta was 12.96 % with Diet 1, 53.66 % with Diet 2 %, and 8.23 % with Diet 3. The stable isotopes analysis showed that Diet 1 resulted in the lowest δ13C‰ values, whereas the δ15N‰ values were not significantly different among the three groups, indicating that there were differences in the food compositions of the juvenile crabs with the different feeding modes. The main food source for juvenile crabs fed Diet 1 was A. philoxeroides, with an average contribution of 28.91 % whereas that for juvenile crabs fed Diets 2 and 3 was the formulated feed, with average contributions of 33.35 % and 33.15 %, respectively. Particulate organic matter was the secondary food for all three diets. Therefore, in the juvenile crab pond culture feeding mode, the addition of a formulated feed when A. philoxeroides has a contribution ratio of 10.39 % can improve feed utilization. This study can provide a scientific reference and theoretical basis for the promotion of the formulated feed feeding mode and the development of A. philoxeroides as a vegetal feed added to the formuated feed of juvenile Chinese mitten crabs.