No abstract

In-pond raceway aquaculture (IPRA) is the rational prescription for water eutrophication and improves the pond environment, enhancing production and the quality of fish. This experiment explored the growth performances and muscle quality of grass carp with stocking densities of 32 tail/m3 and 0.07 tail/m2 in IPRA and traditional pond culture (TPC), respectively. The hepatosomatic index, visceral mass ratio, and correction factor were statistically similar in IPRA compared to TPC. While the weight gain rate (p < 0.001) and the content of crude lipid (p < 0.05) in the flesh of grass carp were observed to be statistically promising in IPRA, the pH and water holding capacity, as well as hardness and chewiness, in grass carp muscle were not significantly different between the two culture systems. However, the 2-MIB concentration in the muscle was observed to increase continuously for the complete culture period in IPRA. The abundance of Proteobacteria was found to be higher in TPC (p < 0.05), while the richness of Planctomycetes was superior in IPRA (p < 0.05). Despite the high stocking density, the off-flavor in IPRA-produced grass carp had less of an impact on the flesh aesthetic quality compared to TPC. Considering all these facts, the results of this study show that grass carp with a better muscle quality can be produced from IPRA.

The starter diet for Japanese eel (Anguilla japonica) has always been a difficult problem for the realization of total artificial reproduction. Therefore, this research analyzed the nutritional composition of artificially fertilized eggs, and transcriptome of samples from early hatchlings of fry to better understand nutrients requirements. The composition of crude lipid and crude protein in fertilized eggs was 7.24% and 10.56%, respectively. Seven kinds of essential amino acids (EAA) were detected but took a comparable lower content (3.19%) than other marine fish eggs. We randomly assembled 265.74 million clean reads and identified 1751 differentially expressed genes (DEGs) (P < 0.01) from pre-leptocephalus larvae. A total of 23 KEGG pathways related to the digestive and metabolic system were detected. Genes related to the secretion pathway of saliva, pancreatic juice and other digestive juices were significantly changed. The genes of carbohydrate metabolism, glycerolipid metabolism and glycerophospholipid metabolism were up-regulated significantly with the growth of the larvae (day 0 to 12). This study will facilitate future studies on the nutrition of eel larvae and other biological traits to reproductive research.