The complete mitochondrial genome sequence of the hybrid of Acipenser schrenckii (♀) × Huso dauricus (♂) (A × H) was first determined by a PCR-based sequencing method in this study. The mitochondrial was 16 687 bp in length, including 13 protein genes, two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and one control region. All genes were encoded on the heavy strain except for ND6 and eight tRNA genes. Base composition of the heavy strain was A (29.80%), T (24.42%), C (28.94%), G (16.82%), and with A + T bias of 54.26%. Compared with the complete mitochondrial genome of the parents, results showed the hybrid sturgeon was consistent with a maternal inheritance; however, we also found ND6 and tRNA-Glu which were species-specific for the male parent H. dauricus. The complete mitochondrial genome sequence of the A × H provided an important data set for further study in mitochondrial inheritance mechanism.

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The complete mitochondrial genome of Ictiobus cyprinellus was first determined by a polymerase chain reaction-based sequencing method in this study. The mitochondria was 16,611 bp in length, including 13 protein genes, 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and 1 control region. All genes were encoded on the heavy strain except for ND6 and eight tRNA genes. The gene arrangement of I. cyprinellus was similar to those found in the other Catostomidae species. Base composition of the heavy strain was A (29.40%), T (24.86%), C (27.96%), G (17.78%) and with A + T bias of 54.26%.

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The supply of a balanced portion of nutrition is vital for the success of the restocking program of the Yangtze sturgeon, an endangered sturgeon in the Yangtze River, however, knowledge of the nutritional requirement of this endangered species is scarce. The present study was performed to investigate the optimum dietary lipid requirement of the Yangtze sturgeon juveniles (initial weight, 184.24 ± 6.79 g). Five isonitrogenous diets containing a mixture of fish oil and soybean oil (1:1 ratio) at five different levels (35, 63, 90, 124 and 168 g/kg) were prepared and each prescribed diet was hand‐fed to triplicate groups of fish for 50 days. Results showed that feed intake of fish was not affected, but growth and feed utilization rate increased and then declined with the increment of dietary lipid content. Similar trends were observed for the activities of enzymes involved in lipid digestion and metabolism. The lipid content of fish dorsal muscle and liver together with serum triglyceride content was linearly elevated with increasing inclusion of dietary lipid. The inclusion of 12.4% dietary lipid significantly reduced the content of deamination product ammonia in serum. Excessive lipid intake caused noticeable hepatocellular vacuolation as shown by histological staining. Based on the regression analysis between growth response and dietary lipid levels, the optimum dietary lipid level of juvenile Yangtze sturgeon was estimated to be 141.67 g/kg diet.