To investigate the changes in digestive enzyme activities in the intestine and stomach, as well as the activities of non-specific immunoenzymes in the liver of juvenile Sebastiscus marmoratus under salinity stress, and to assess the ability of the juveniles to adapt to sudden changes in salinity, a salinity experiment was conducted. The experiment comprised four groups, representing different salinity gradient levels: 6, 8, 10, and 20 (control). These groups were referred to as S6, S8, S10, and S20, respectively. Results indicated that at the acute stress period of 96 hours, the activities of trypsin, pepsin, amylase, and lipase in S10 and S20 were significantly higher compared to those in S6 and S8 (P<0.05). Conversely, the activities of glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase were significantly higher in S6 and S8 compared to S10 and S20 (P<0.05). There was no significant difference in the activities of ACP and AKP between S6 and S8 (P>0.05). Additionally, the activities of ACP and AKP increased initially and then decreased over time in S10 and S20. These activities in S10 and S20 peaked at 12 hours, signifying a significant increase compared to other salinity levels. These findings suggest that the optimal salinity for breeding juvenile S.marmoratus ranges from 10 to 20.

In order to investigate the genetic diversity among three populations of Macrobrachium rosenbergii collected from Shanghai breeding population (SC), Zhejiang cultured population (ZJ) and Thailand wild population (TL), the mitochondrial sequences of the COⅠ gene in the three populations were amplified and determined by PCR and sequencing. The result showed that 8 nucleotide sites and 4 haplotypes were found in the 458 bp long partial gene segment. The mean content of A+T (54.4%) was higher than G+C (45.7%). Genetic variation parameters showed the population of highest haplotype diversity was TL population (Hd=0.733), the population of highest nucleotide diversity was ZJ population (π=0.005). AMOVA showed that genetic variations among populations (74.5%) was higher than that within populations (25.5%). The tendency of molecular phylogenetic trees which were constructed by NJ and UPMGA method was similar. SC population and ZJ population were the closest genetically, and they clustered into a small branch, then with TL population. These findings were expected to provide reference information for the protection and utilization of germplasm resources of M.rosenbergii.