Crayfish, carp, and crab threaten the consumer’s health due to the enrichment of the toxic elements. The concentration of the toxic elements (As, Cr, Cd, and Pb) in these aquatics was less investigated simultaneously in situ. In this study, the toxic elements in these aquatics from the same site of Hanchuan, Hubei Province, China were measured by ICP-MS to assess the enrichment of the four toxic elements in them and the health risk to the consumer. The results showed that the concentrations of these elements in muscle were lower than those in hepatopancreas/ liver, except for Cr in crayfish. Furthermore, the concentrations of Cd in the hepatopancreas of crayfish and crab exceeded the standards of China and the European Union. Accordingly, the hepatopancreas of crayfish and crab are not recommended for consumption. The estimated daily intake of these elements in the muscle of crayfish, carp, and crab did not exceed the provisional tolerable daily intakes, the corresponding target hazard quotient (THQ), and the cancer risk (CR) values for As were lower than 1 and 1 × 10–6, respectively. However, the accumulated consumption of the muscle of the three freshwater catches could result in a significant increase in the total THQ value. The total ingestion of the muscle of these catches should be limited. Collectively, these findings may renew interest in food safety and the health risk to humans owing to the consumption of freshwater catches.

The red swamp crayfish, Procambarus clarkii (Girard, 1852), is currently an economically important aquaculture animal. Its genetic basis has been scarcely reported, however, partly due to the absence of abundant molecular markers in the genome. In this study, Simple Sequence Repeat (SSR) loci were mined, based on genome survey sequencing via the next generation sequence of the red swamp crayfish. A total of 4897 SSR loci were identified, with the most abundant type being the di-nucleotide repeat motifs (75.2%), followed by tri- (20.4%), tetra- (3.8%), penta- (0.5%), and hexanucleotide (0.2%) repeats. In total, 1546 SSR markers were validated to be amplified, and 721 of these were identified as polymorphic SSR markers. Fifty polymorphic SSR markers were randomly selected for the identification of the genetic diversity of the 14 red swamp crayfish populations in China. The expected and observed heterozygosity and polymorphism information content were 0.39, 0.30, and 0.29, respectively, on average. The results indicated a medium genetic diversity among the 14 investigated populations. These probably cluster into three genetic populations. The current study provides abundant genetic markers and information on the 14 populations, which can be helpful for genetic diversity estimation and molecular breeding of the red swamp crayfish.