The invasive golden apple snail Pomacea canaliculata has a strong reproductive capacity and has rapidly spread in Asian countries. Current control methods include physical, chemical, and biological approaches, but there has been limited research on the control of P. canaliculata in its different life stages. This study assessed the effectiveness of using giant river prawns Macrobrachium rosenbergii in controlling juveniles of P. canaliculata through a controlled indoor experiment. The density, size, and dispersal range of recently hatched juvenile snails were significantly lower among those kept with prawns than those kept without prawns, indicating a control effect of M. rosenbergii at least on P. canaliculata juveniles. Furthermore, the study speculates on the potential application of M. rosenbergii in the context of a rice–prawn symbiotic system of ecological farming to control invasive P. canaliculata. In terms of effectiveness and safety, its application might lead to a win-win situation for both rice-farm profits and the ecological benefits of invasive species control.

Microalgae play an important role in the formation of biofloc. To demonstrate the feasibility of Chlorella pyrenoidosa in biofloc formation, an experiment was performed with a simple random design consisting of five inoculation levels (in triplicate) of C. pyrenoidosa (0, 1 × 10⁸, 1 × 10⁹, 5 × 10⁹, and 1 × 10¹⁰ cells·L⁻¹) in the biofloc system. All treatments kept a C:N ratio of approximately 15:1. This study observed the effects of different initial concentrations of C. pyrenoidosa on biofloc formation, water quality and bacterial community in biofloc systems. The results indicated that C. pyrenoidosa had the ability to enhance biofloc development, especially when the C. pyrenoidosa initial concentration reached 5~10 × 10⁹ cells·L⁻¹. Too high or too low a concentration of C. pyrenoidosa will adversely affect the formation of biofloc. The effect of C. pyrenoidosa addition on water quality (TAN, NO₂⁻-N, and NO₃⁻-N) was not significant in the final stage. The inoculation of C. pyrenoidosa decreased the species richness and diversity of the bacterial community but increased the domination of Proteobacteria and Bacteroidota in the biofloc system, especially the order of Rhizobiales. The addition of C. pyrenoidosa could maintain water quality by increasing the proportion of several denitrifying bacteria, including Flavobacterium, Chryseobacterium, Pseudomonas, Brevundimonas, Xanthobacter, etc. These above dominant denitrifying bacteria in the biofloc system could play a major role in reducing the concentration of NO₂⁻-N and NO₃⁻-N. So, we recommended the reasonable concentration is 5~10 × 10⁹ cells·L⁻¹ if C. pyrenoidosa is used to rapidly produce biofloc.

As a typical pathogen-associated molecular pattern (PAMP), β-1,3-glucan can engage with pattern recognition receptors (PRRs) to initiate an immune response. In this study, we investigated the effects of dietary β-1,3-glucan on growth performance, antioxidant capacity, immune response, intestinal health, and bacterial resistance in juvenile Macrobrachium nipponense. Prawns were fed with five experimental diets containing 0%, 0.05%, 0.1%, 0.2%, and 0.4% β-1,3-glucan for eight weeks. The findings demonstrated that the inclusion of β-1,3-glucan improved weight gain and survival rate in prawns. Prawns fed with β-1,3-glucan exhibited elevated activities of hepatopancreatic ACP (acid phosphatase), AKP (alkaline phosphatase), and SOD (superoxide dismutase), while MDA (malondialdehyde) content was reduced. Expression levels of PRRs related genes including LGBP (lipopolysaccharide and β-1,3-glucan binding protein), lectin, and LBP (lipopolysaccharide-binding protein) were significantly increased in prawns fed with β-1,3-glucan. Intestinal flora analysis revealed suppression of Cyanobacteria abundance at the Phylum level and enhancement in Rhodobacter abundance at the genus level in prawns fed with a 0.2% β-1,3-glucan diet. Furthermore, prawns fed with 0.1%, 0.2%, and 0.4% β-1,3-glucan demonstrated significantly higher survival rates following Aeromonas hydrophila infection. In conclusion, β-1,3-glucan can activate PRRs to improve immune responses in M. nipponese. Within the range of β-1,3-glucan concentrations set in this experiment, it is recommended to add 0.18% of β-1,3-glucan to the diet, taking into account the positive effect of β-1,3-glucan on the survival rate of M. nipponensecu.

The use of Auxenochlorella pyrenoidosa (formerly Chlorella pyrenoidosa) and its intracellular substances (ISs) to promote biofloc development has been extensively studied. To identify the key components of the ISs of A. pyrenoidosa that drive biofloc formation, algal-extracted polysaccharides (AEPSs) and algal-extracted proteins (AEPTs) were isolated from the ISs. In this study, we established four groups: ISs, AEPSs, AEPTs, and tap water (TW, control), to investigate the effects of AEPSs and AEPTs on biofloc formation dynamics, water quality parameters, and microbial community composition. The results indicated no significant differences were observed between the ISs and AEPSs groups during the cultivation period. AEPSs significantly enhanced flocculation efficiency, achieving a final floc volume of 60 mL/L. This enhancement was attributed to the selective promotion of floc-forming microbial taxa, such as Comamonas, which can secrete procoagulants like EPS, and Pseudomonas and Enterobacter, which have denitrification capabilities. Water quality monitoring revealed that both AEPSs and AEPTs achieved nitrogen removal efficiencies exceeding 50% in the biofloc system, with AEPSs outperforming AEPTs. This is closely related to the fact that the microorganisms with increased flocculation contain numerous nitrifying and denitrifying bacteria. So, the intracellular polysaccharides were the key component of the ISs of A. pyrenoidosa that drive biofloc formation. These findings provide critical insights into the functional roles of algal-derived macromolecules in biofloc dynamics and their potential applications in wastewater treatment.

In recent years, Pomacea canaliculata has aggressively invaded rice fields in Asia, resulting in significant agricultural losses. Biological control can effectively reduce the damage caused by P. canaliculata. This research evaluates E. sinensis as a biocontrol for P. canaliculata, focusing on its feeding preferences and optimal control density on snails of three sizes, as well as the effects on the nutritional quality of juvenile crabs post consumption. Our findings reveal that juvenile E. sinensis exhibit a strong preference for feeding on small snails, effectively managing populations at densities of 600 snails per tank. Crab feeding significantly reduces the survival and activity of snails. Furthermore, consumption of P. canaliculata meat alters the crabs’ physiology. Female crabs show elevated levels of molting hormones, total energy yield (TEY), and condition factor (CF), while males demonstrate increased lipid, moisture, and TEY levels. The amino acid profiles shift, with higher isoleucine and leucine levels in female hepatopancreas and reduced histidine in the muscles. Notably, the total Σn-3 PUFA content in female muscles fed on snail meat exceeds that of those given commodity grain. This study underscores the dual benefits of employing juvenile E. sinensis for managing P. canaliculata while enhancing crab farming practices.

Pollution evaluation and health risk assessment are critical procedures for residents consuming black carp (Mylopharyngodon piceus) contaminated with non-essential hazardous trace elements in an artificial wetland also known as an aquaculture pond. Samples were collected, dissected and digested to analyze the pollution status and health risk associated with four heavy metals present in eleven tissues of black carp fish based on the metal pollution index (MPI) and target hazard quotient (THQ). The results indicated that the concentrations of Cd, Cr, Cu and Pb were 1.36 ± 0.04 mg/kg, 13.70 ± 0.50 mg/kg, 2.85 ± 0.10 mg/kg, and 4.98 ± 0.18 mg/kg in large black carp, while the concentrations of Cd, Cr, Cu and Pb were 4.27 ± 0.08 mg/kg, 50.84 ± 0.82 mg/kg, 9.33 ± 0.18 mg/kg, and 22.49 ± 0.42 mg/kg in small specimens. The MPI values showed that the heavy metal pollution detected in small fish was much more significant than in large fish. Notably, the polluted metals were more likely to accumulate in the viscera (e.g., brain and heart) rather than in the external tissues (e.g., muscle and epidermis). In addition, the estimated THQ and HI values for three edible tissues demonstrated that the health risk associated with muscle tissue intake of both small and large black carp was within the acceptable range, while the contaminants were likely to pose health risks associated with the consumption of fish head tissue. Small black carp are generally not fit for human consumption, thus both the epidermis and muscle of the fish are often cooked in China. However, the ingestion of large black carp is relatively safe. The contributions to THQ values of these four heavy metals decreased in the following sequence: Cr > Pb > Cd > Cu. Cr is the critical pollutant with its contribution to HI values measuring over 50%. We suggest that in artificial wetlands (e.g., aquaculture ponds) more attention should be paid to heavy metal pollution, the conservation of the aquaculture ecosystem, and effects on human health.