Intensive Culture Research Articles

Effects of Bacillus subtilis as a single strain probiotic on growth, disease resistance and immune response of striped catfish (Pangasius hypophthalmus).

The present study investigated the potential role of Bacillus subtilis as probiotic in striped catfish (Pangasius hypophthalmus). Fish (initial weight = 150.00±2.63g n = 180) were stocked in circular tanks. Four isonitrogenous (30%) and isolipidic (3.29%) diets were formulated having supplementation of B. subtilis at four different levels (P0; 0, P1: 1×106, P2: 1×108 and P3: 1×1010 CFU/g). Each treatment had three replicates, while each replicate had fifteen fish. The trial started on second week of July and continued for eight weeks. Growth, feed conversion ratio, crude protein content, the concentration of amylase and protease, the profile of both dispensable and non-dispensable amino acids in all four dietary groups increased with a gradual increase of B. subtilis in the diet. At the end of growth experiment, fish in all four groups were exposed to Staphylococcus aureus (5×105 CFU/ml). After S. aureus challenge, fish fed with B. subtilis responded better to damage caused by reactive oxygen species and lipid peroxidation and better survival rate. The catalase and superoxide dismutase level also increased in response to bacterial challenge in B. subtilis fed groups. On the other hand, the concentration of malondialdehyde gradually decreased in these groups (+ve P0 >P1>P2>P3). It is concluded that supplementation of B. subtilis as a probiotic improved the growth, protein content, antioxidant response and immunocompetency against S. aureus in striped catfish. The optimum dosage of B. subtilis, at a concentration of 1×1010 CFU/g, resulted in the most favorable outcomes in striped catfish. This single bacterial strain can be used as an effective probiotic in large scale production of aquafeed for striped catfish. Future studies can investigate this probiotic's impact in the intensive culture of the same species.

Effects of intensive oyster farming on nitrogen speciation in surface sediments from a typical subtropical mariculture bay

The spatial-temporal distributions of various nitrogen (N) species in surface sediments were examined in a typical subtropical mariculture bay (Maowei Sea) in the northern Beibu Gulf to assess the impact of intensive oyster culture activities on sedimentary N speciation. The results indicated that the mean contents of total nitrogen (TN), extractable (labile) nitrogen (LN) and residual nitrogen (RN) in the surface sediments were 33.3 ± 15.5 μmol g−1, 13.8 ± 1.3 μmol g−1 and 19.5 ± 15.0 μmol g−1, respectively, which lacked significant seasonal variability (P > 0.05). Four forms of LN, namely ion extractable form (IEF-N), weak acid extractable form (WAEF-N), strong alkali extractable form (SAEF-N) and strong oxidant extractable form (SOEF-N) were identified based on sequential extraction. SOEF-N was the dominant form of LN, accounting for 67.8 ± 2.5 % and 63.7 ± 5.9 % in summer and winter, respectively. Spatially, the contents of sedimentary TN, LN, RN, WAEF-N and SOEF-N in intensive mariculture areas (IMA) were significantly higher than those in non-intensive mariculture areas (NIMA) during summer (P < 0.05). Stable nitrogen isotope (δ15N) mixing model revealed that shellfish biodeposition was the predominant source of sedimentary TN in IMA with a contribution of 67.8 ± 23.0 %, approximately 5.4 times that of NIMA (12.6 ± 3.3 %). Significant positive correlations (P < 0.05) were observed between most forms of N species (WAEF-N, SOEF-N, LN and RN) and shellfish-biodeposited N in the surface sediments during summer, indicating that intensive oyster farming greatly enhanced sedimentary TN accumulation.

Ammonia‐‑nitrogen stress affects immune regulation via TNFα in yellow catfish (Pelteobagrus fulvidraco)

Ammonia‑nitrogen has become a global issue with feed-dependent intensive culture modes, which may cause toxicity in aquatic animals by affecting immune regulation. Although numerous studies have investigated the acute and short-term toxic effect of ammonia‑nitrogen in fish, there is a lack of research on the long-term effects of exposure to low concentration of ammonia‑nitrogen. In this study, yellow catfish (Pelteobagrus fulvidraco) were exposed to water supplemented with ammonia (NH4Cl was used as the ammonia source) at concentrations of 0 (control), 8, 10, 12, 14, 16 and 18 mg/L for eight-weeks, and the effects on growth performance, histopathology, antioxidant and immune capacities of yellow catfish were investigated. The results showed that long-term ammonia exposure resulted in decreased weight gain rate (WGR) and serum antioxidant capacity, increased feed coefficient (FC), serum and tissue ammonia levels. They caused extensive histopathological changes and significantly impaired inflammatory and immune responses. On the other hand, ammonia exposure significantly affected the respiratory burst and the content of reactive oxygen species (ROS) of head kidney macrophages. Still, the above phenomenon can be reversed by inhibiting tumor necrosis factor-α (TNFα), indicating that TNFα may play a key role in this process. In conclusion, our findings indicate that extended exposure to ammonia nitrogen, even at low concentrations, has a detrimental effect on the well-being of aquatic organisms. This finding underscores the necessity of long-term environmental toxicological investigations of ammonia‑nitrogen.

Unlocking Eco-solutions: Analyzing parasitic disease resistance in Yellow River carp (Cyprinus carpio haematopterus) under different ecological treatments

Combatting parasitic diseases in intensive aquaculture is crucial for sustainable and healthy fish production. The use of chemical pesticides, although effective, poses environmental and public health risks. To address this issue, we investigated the impact of ecological treatments on the occurrence of parasitic diseases in intensive culture of Yellow River carp (Cyprinus carpio haematopterus) pond. A comprehensive survey was conducted in 160 ponds, and the data were collected through a normative questionnaire which included the main factors related to ecological management such as pond water sources and depth, stocking methods, whether or not mixed culture with carps, water quality adjustment and sediment operation methods. Whether parasitic diseases have happened was determined by combination of both field investigation and laboratory diagnostic methods. For assessment the relationship between ecological treatments and parasitosis occurrence, the data were analyzed using two methods, including univariate and multivariate logistic regressions. The final model revealed the influence of five significant ecological treatments (P < 0.05) on parasitosis occurrence in the ponds. The three ecological treatments significantly reduced disease occurrence, which were mixed culture with silver and/or bighead carp, maintaining water quality at intervals of ≤7 days, and aeration time > 10 h in 24 h. Additionally, utilizing underground water, avoiding sediment stirring increased the incidence of the parasitosis. These findings demonstrate the effectiveness of appropriate ecological treatments in minimizing parasitic diseases in Yellow River carp, supporting sustainable aquaculture development.

The Probiotic Bacillus hwajinpoensis Colonizes the Digestive System of Crassostrea gigas Larvae and Protects Them from Vibrio alginolyticus Infection.

The Pacific oyster Crassostrea gigas is one of the most important cultured marine species around the world. Production of Pacific oysters in China has depended primarily on hatchery produced seeds since 2016, with the successful introduction and development of triploid oysters. However, the seed supply of Pacific oysters is threatened by recurring mass mortality events in recent years. Vibriosis is the most commonly encountered disease associated with intensive oyster culture in hatcheries and nurseries. Vibrio alginolyticus and Bacillus hwajinpoensis were the two strains with pathogenic and probiotic effects, respectively, identified during the Pacific oyster larvae production. To monitor their colonization process in Pacific oyster larvae, green fluorescent protein (GFP) and red fluorescent protein (RFP) were labeled to the pathogenic V. alginolyticus and the probiotic B. hwajinpoensis stain, respectively. The pathogenic and probiotic effects of the two strains during the colonization process were then assessed. Stabile expression of GFP and RFP were observed in corresponding stains, and the capabilities of growth, biofilm formation and in vitro adhesion of GFP- and RFP- tagged stains were not significantly different from those of the wild-type strains. Usage of probiotics of 105 CFU/mL significantly inhibited the growth of pathogenic V. alginolyticus and reduced the mortality of D-sharped larvae. Both the pathogenic and probiotic strains employed a similar route to enter and colonize the oyster larvae, which indicates that competing with pathogens for binding and spreading sites were one of the mechanisms of B. hwajinpoensis to provide the probiotic effects to oyster larvae. In summary, employment of fluorescence-tagged pathogenic and probiotic strains simultaneously provides us with an excellent bioassay model to investigate the potential mechanisms of probiotics.

Occurrence and health risks of heavy metals in crayfish (Procambarus clarkii) from Jiangsu province, China

Concentrations of arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) in crayfish from Jiangsu province, China, were measured and their health risks were evaluated. For crayfish from both crayfish-rice culture system (CRCS) and crayfish intensive culture system (CICS), concentrations of As, Cd and Pb in whole body of crayfish (WB) were significantly higher than those in abdominal muscle of crayfish (AM), while concentration of Hg in WB was significantly lower than that in AM. No significant difference in concentrations of the heavy metals was found between CRCS and CICS. Concentrations of the heavy metals in AM from both systems were below the limit set by the national standard of China. Estimated daily intake values of the heavy metals were far below the provisional tolerable daily intakes set by Joint FAO/WHO committee on Food Additives, and the corresponding hazard quotient and hazard index were below one. Therefore, consumption of crayfish with the average daily consumption rate (DCR) could be generally regarded as safe. For the consumption with two more times of average DCR during peak season, there might be a potential health risk from intakes of As and Hg in abdominal muscle of crayfish.Graphical

Polymer Gel Substrate: Synthesis and Application in the Intensive Light Artificial Culture of Agricultural Plants.

This work is devoted to the description of the synthesis of hydrogels in the process of cryotropic gel formation based on copolymerization of synthesized potassium 3-sulfopropyl methacrylate and 2-hydroxyethyl methacrylate (SPMA-co-HEMA) and assessing the potential possibility of their use as substrates for growing plants in intensive light culture in a greenhouse. Gel substrates based on the SPMA-co-HEMA were created in two compositions, differing from each other in the presence of macro- and microelements, and their effects were studied on the plants' physiological state (content of chlorophylls a and b, activity of catalase and peroxidase enzymes, intensity of lipid peroxidation, elemental compositions) at the vegetative period of their development and on the plants' growth, productivity and quality of plant production at the final stages of development. Experiments were carried out under controlled microclimate conditions. Modern and standard generally accepted methods of gels were employed (ATR-FTIR and 13C NMR spectral studies, scanning electron microscopy, measurement of specific surface area and pore volume), as well as the methods of the physiological and chemical analysis of plants. The study demonstrated the swelling ability of the created gel substrates. Hydrogels' structure, their specific surface area, porosity, and pore volume were investigated. Using the example of representatives of leaf, fruit and root vegetable crops, the high biological activity of gel substrates was revealed throughout the vegetation period. Species specificity in the reaction of plants to the presence of gel substrates in the root-inhabited environment was revealed. Lettuce, tomato and cucumber plants were more responsive to the effect of the gel substrate, and radish plants were less responsive. At the same time, more pronounced positive changes in plant growth, quality and productivity were observed in cucumber and lettuce in the variant of gel substrates with macro- and microelements and in tomato plants in both variants of gel substrates. Further research into the mechanisms of the influence of gel substrates on plants, as well as the synthesis of new gel substrates with more pronounced properties to sorb and retain moisture is promising.

Evaluation of High Stocking Densities on the Water Quality and Growth Performance of Pacific White Shrimp Litopenaeus vannamei Reared in a Mixotrophic Biofloc Nursery System

The present study aimed to explore the effects of intensive culture densities on the water quality and growth performance of the Pacific white shrimp Litopenaeus vannamei reared in a mixotrophic biofloc system (heterotrophic/chemoautotrophic) at three stocking rates of 5,000, 4,000, and 3,000 PL/m3 (namely G5000, G4000, and G3000, respectively) for 21 days. At the end of the study, the mean values of water temperature, dissolved oxygen, dissolved oxygen saturation level, pH, oxidation-reduction potential, free carbon dioxide, alkalinity, total ammonia nitrogen (TAN), nitrite-nitrogen (NO2-N), nitrate-nitrogen, and settleable solids did not substantially differ among study groups ( p &gt; 0.05 ). In addition, the highest mean levels of TAN and NO2-N recorded were 1.27 mg/l (G4000) and 9.23 mg/l (G3000), respectively. The results of growth performance revealed that final body weight, weight gain, weekly growth rate, and specific growth rate were not affected by the studied densities ( p &gt; 0.05 ). Although no significant differences were observed ( p &gt; 0.05 ), the G3000 treatment exhibited the highest survival rate (80.66% ± 8.56%), followed by G4000 (75.05% ± 0.31%) and G5000 (71.63% ± 2.11%). However, the shrimp yield was meaningfully higher for G5000 treatment (1.72 ± 0.0.09 kg/m3, 0.69 ± 0.03 kg/m2) compared with G3000 group (1.27 ± 0.0.12 kg/m3, 0.48 ± 0.04 kg/m2) ( p &lt; 0.05 ). Our results indicate L. vannamei can be reared at intensive nursery densities of up to 5,000 PL/m3 (2,000 PL/m2) until reaching 0.5 g without significant retardation in water quality, growth, and survival.

Molecular epidemiology and current management of Infectious Spleen and Kidney Necrosis Virus (ISKNV) infection in Ghanaian cultured tilapia

Infectious Spleen and Kidney Necrosis Virus (ISKNV) is globally gaining more attention, due to its highly significant economic impact on the aquaculture industry. In late 2018, unusually high levels of mortality (60–90%) was reported in some intensive tilapia cage culture systems on the Eastern bank of Lake Volta in Ghana. This resulted in the fold-up of several small and medium scale farms. Preliminary investigations confirmed the involvement of ISKNV, a viral pathogen noted for fatal systemic infections in many fish species. As a follow-up on the outbreak situation, and post-mass vaccination of affected fish farms, the need to investigate further the molecular epidemiology and phylogeography of the virus across Lake Volta became paramount. A multiplexed PCR assay to detect the virus and MinION™ nanopore sequencing of the Major Capsid Protein (MCP) were performed to investigate the presence and genotype of ISKNV in tilapia collected from 30 randomly selected farms at various geographical locations. ISKNV was found to be widely distributed across the lake and detected in 80% of farms with a reported average daily mortality of 40%. Fry and juvenile fish were the most affected, and approximately 50% of fish that tested positive were asymptomatic. These apparently healthy fish are likely contributors of virus transmission across farms. Phylogenetic analysis of the MCP revealed that all 35 isolates from 14 different farms distributed across the lake clustered with ISKNV clade I with 100% homology to isolates from the 2019 outbreak strain. Vaccination and heat-shock treatment; the two main specific interventions currently employed to control the viral pathogen have not achieved much success, and ISKNV remains a threat to the growth of the aquaculture industry in Ghana. The outcome of this study can be useful in improving fish health management and biosecurity policies in the aquaculture industry.

Skeletal Morphogenesis and Anomalies in Gilthead Seabream: A Comprehensive Review.

The gilthead seabream, one of the most important species in Mediterranean aquaculture, with an increasing status of exploitation in terms of production volume and aquafarming technologies, has become an important research topic over the years. The accumulation of knowledge from several studies conducted during recent decades on their functional and biological characteristics has significantly improved their aquacultural aspects, namely their reproductive success, survival, and growth. Despite the remarkable progress in the aquaculture industry, hatchery conditions are still far from ideal, resulting in frequent abnormalities at the beginning of intensive culture, entailing significant economic losses. Those deformities are induced during the embryonic and post-embryonic periods of life, and their development is still poorly understood. In the present review, we created a comprehensive synthesis that covers the various aspects of skeletal morphogenesis and anomalies in the gilthead seabream, highlighting the genetic, environmental, and nutritional factors contributing to bone deformities and emphasized the potential of the gilthead seabream as a model organism for understanding bone morphogenesis in both aquaculture and translational biological research. This review article addresses the existing lack in the literature regarding gilthead seabream bone deformities, as there are currently no comprehensive reviews on this subject.

Transcriptomic analysis revealed the dynamic response mechanism to acute ammonia exposure in the ivory shell, Babylonia areolata

The ivory shell (Babylonia areolata) is an economically important shellfish in tropical and subtropical regions, but its intensive culture and biological characteristic of hiding in the sandy substrate make it highly susceptible to ammonia stress. In this study, we investigated the dynamic changes in histopathology, oxidative stress, and transcriptome of the ivory shell at different time points under high concentration (60 mg/L) ammonia exposure. With prolonged exposure to stress, vacuoles appeared in the hepatopancreas while cell volume and intercellular space increased. The activities of superoxide dismutase (SOD) and catalase (CAT) decreased significantly under high concentrations of ammonia-induced stress while malondialdehyde (MDA) levels increased significantly. Integrated analysis of differentially expressed genes (DEGs), weighted gene co-expression network analysis (WGCNA), and quantitative real-time polymerase chain reaction (qRT-PCR) revealed that lipid transport primarily contributed to maintaining cellular homeostasis during the early stage of stress (6 and 12 h). Subsequently, a significant upregulation of oxidation-reduction reactions occurred at the middle stage (24 h), leading to oxidative stress. Finally, during the later stage (48 h), metabolic decomposition provided energy for survival maintenance. Additionally, lysosome and apoptosis were identified as potential key pathways in response to acute ammonia toxicity. Overall, our findings suggest that ivory shells can respond to acute ammonia toxicity via immune and antioxidant defense mechanisms but sustained high concentrations may cause irreversible damage. This study provides valuable insights into the response mechanism of mollusks towards ammonia and serves as a data reference for breeding ammonia-tolerant varieties of ivory shells.

Larval digestive system ontogeny and early weaning in neon tetra Paracheirodon innesi.

The intensive culture of characid teleosts for ornamental trade is highly dependent on live feed organisms, particularly Artemia nauplii, to provide nutrition through the larval stage. Live feeds have inherent disadvantages relative to prepared microparticulate diets (MDs), specifically availability, labor and cost. In this research, the dependence of larval Paracheirodon innesi on live Artemia was confirmed via a nutritional trial. Next, digestive system ontogeny was characterized from the onset of exogenous feeding through metamorphosis. P. innesi exhibited an agastric larval stage, as well as low digestive enzyme activity at the onset of exogenous feeding followed by abrupt increases in trypsin, lipase and pepsin activity. Differentiation of the stomach, including gastric gland formation and production of neutral mucopolysaccharides, as well as the onset of pepsin activity, did not occur until 20days post hatch (dph; 5.24 ± 0.20mm). This shift from agastric to gastric digestive modes is indicative of a proliferation of digestive capacity and subsequent prey diversity in other fish species exhibiting similar altricial larval stages.Based on this information, different schedules for weaning from Artemia to a MD were evaluated. For P. innesi fed until 32 dph, weaning beginning at 12 dph and 17 dph resulted in similar survival to live Artemia (mean: 22.0 ± 1.7%), and the MD resulted in the lowest survival (0.8 ± 0.3%). These results indicate that weaning is possible prior to gastric differentiation, potentially resulting in the reduction of Artemia use in the larval culture P. innesi.

Concentration of suspended solids in superintensive culture of the Pacific white shrimpLitopenaeus vannameiwith biofloc technology (BFT): A review

AbstractMicrobial flocs (bioflocs) present in the water of intensive culture tanks are formed by a variety of microorganisms and other kinds of particulate organic matter, such as faeces and uneaten feed. During shrimp culture, biofloc concentrations increase. It has been reported that some level of control over biofloc levels, which can be quantified by the concentration of total suspended solids (TSS), is necessary for the adequate performance of the system. Some authors suggest that TSS concentrations below 600 mg L−1are more appropriate for the superintensive culture of the Pacific white shrimpLitopenaeus vannameiin biofloc technology (BFT). However, subsequent research results contradict some of the arguments supporting the suggested solids limits, for example, the impact of increased solids on gill obstruction and subsequent shrimp survival. Recent studies have also shown the relationship between the control of solids and other important aspects of the system not considered so far, such as the control of opportunistic bacteria. Therefore, this topic seems worthy of revisiting, and it will be helpful to find new guidance toward understanding the levels of bioflocs that should be kept inL. vannameiculture tanks. In this review, we addressed the reasons that led to the establishment and limitations of the current biofloc levels forL. vannameiculture. The effects of maintaining low and high levels of bioflocs on both shrimp performance and the culture system are also analysed. Finally, perspectives on the management of biofloc levels are discussed, highlighting the advantages and disadvantages of each proposed strategy.

Molecular characterization and expression of Megalobrama amblycephala (Wuchang bream) lysine monomethylase set7 and its potential role in hypoxia adaptation

Previously, we reported that the mammalian lysine monomethylase SET7 impairs the transcriptional activity of hypoxia-inducible factor (HIF), and set7-deficient zebrafish exhibit enhanced tolerance to hypoxia stress. Megalobrama amblycephala, an extensively farmed endemic species in China, is highly sensitive to hypoxia stress, which has posed a serious threat to its intensive and large-scale culture. Therefore, it is meaningful to identify key candidate genes related to the hypoxia tolerance trait in Megalobrama amblycephala. In this study, we found that set7 is highly conserved across species. The luciferase reporter assay showed that Megalobrama amblycephala set7 inhibits the transcriptional activity of hif-1αa/b and hif-2αa/b. Furthermore, using the fluorescent glucose analog 2-NBDG, we observed that overexpression of Megalobrama amblycephala set7 inhibited glucose uptake in EPC cells under hypoxic conditions. Our findings may provide clues to understand the function of Megalobrama amblycephala set7 in the hypoxia signaling pathway, and provide a potential target for genetic breeding of hypoxia tolerant species.

Review on Gilthead Seabream (Sparus aurata) Aquaculture: Life Cycle, Growth, Aquaculture Practices and Challenges

Over the years, the gilthead seabream (Sparus aurata), a prominent species in Mediterranean aquaculture with an increasing production volume and aquafarming technologies, has become an important research focus. The accumulation of knowledge via several studies during the past decades on their functional and biological characteristics has significantly improved the aquacultural aspects, namely their reproductive success, survival, and growth. Despite the remarkable progress in the aquaculture industry, hatchery conditions are still far from ideal, resulting in frequent challenges at the beginning of intensive culture, entailing significant economic losses. Given its increasing importance and the persistent challenges faced in its aquacultural practices, a thorough review is essential to consolidate knowledge, and elucidate the intricate facets concerning its distribution, life cycle, growth dynamics, genetics, aquaculture methodologies, economic dimensions, and the challenges inherent to its cultivation.

Effect of digestible protein on intermediate metabolism, hepatic enzyme activities, energy reserves, and growth performance of pacu (Piaractus mesopotamicus) in the finishing growth phase.

This study investigated the effect of different levels of digestible protein (DP) on blood metabolites, hepatic enzyme activity of glycolysis and amino acid metabolism, energy reserves, and the production characteristics of pacu (Piaractus mesopotamicus) during the finishing growth phase. Six semi purified and isoenergetic diets, containing 16.3, 20.1, 23.8, 27.2, 31.5, and 34.8% of balanced DP, provided with essential amino acid balance, were hand-fed to pacu (1100.0 ± 10.3 g, initial weight) three times daily for 7 weeks. The experiment consisted of six treatments, with three randomly arranged replicates (tanks) per treatment. The data obtained from this experiment were analyzed by one-way analysis of variance (ANOVA), and significant differences (p < 0.05) between treatments were determined using Tukey's test. Blood metabolites, except serum ammonia and the hepatic enzymes activities of glycolysis and amino acid metabolism, except hexokinase activity were affected (p < 0.05) by balanced DP. The energy reserve indices, except hepatic total lipid content, were also found associated (p < 0.05) with balanced DP. The test diets significantly (p < 0.05) affected growth performance parameters. Higher dietary proteins led to a greater energy uptake by fish from the protein in feed. Overall, fish fed the intermediate level (23.8%) of balanced DP with digestible energy of 17.95 MJ kg-1 showed better production traits and physio-biochemical health markers. This information could help nutritionists and farmers to develop nutritionally balanced and economically and environmentally sustainable aquafeed for promoting healthy and sustainable production of pacu in intensive culture systems.

Critical temperatures and aerobic metabolism in post-larvae of Pacific white shrimp Litopenaeus vannamei (Boone, 1931).

Increasing water temperature because of climate change decreases the oxygen concentration while increasing the oxygen requirement of species in aquatic environments. Temperature is one of the most important environmental factors affecting the physiological functions of organisms, especially poikilothermic animals, such as shrimp at all levels. In intensive shrimp culture, it is of great importance to know the tolerable temperature range of cultured species and their metabolism since this affects the physiological condition. In this study, critical temperatures (CTM: CTmin and CTmax) of Pacific white shrimp, Litopenaeus vannamei, post-larvae (PL), were determined at different acclimation temperatures of 15, 20, 25, and 30°C. Lower and upper incipient lethal temperatures (ILT: LILT and UILT) were also calculated for the PL. The thermal windows of the PL were developed using the CTM and ILT values. The standard metabolic rate (SMR) of the PL was determined based on the oxygen consumption rate (OCR) at the different acclimation temperatures mentioned above. The acclimation temperature had a subsequent effect on the thermal tolerance and SMR of the PL (P < 0.01). The PLs of Pacific white shrimp have high thermal tolerance and can survive at extreme temperatures (CTmin and CTmax: 8.2-43.8°C) with their large dynamic and static thermal window areas of 1128 and 931°C2, respectively. The optimal temperature range for Pacific white shrimp PLs is the 25-30°C range, where a decrease in SMR is determined with increasing temperature. The result of this study reveals that a range of 25-30°C is optimal for effective PL culture of Pacific white shrimp.

Effects of substrate, water flow, and turbulence in raceway culture of the high-value agarophyte Pterocladiella capillacea

One reason most commercial seaweed aquaculture is done extensively is that land-based intensive culture is expensive. Seaweed growth in land-based raceways can be bolstered by high water flows and turbulence, and a better understanding of this may mitigate production costs. We investigated flow conditions in raceway culture of Pterocladiella capillacea, a source of pharmaceutical grade agar. We tested the effects of ploidy level (carpospores, tetraspores), substrate (rope, glass slide), and flow type in raceways (turbulent, laminar) and the laboratory (no flow) on the survival and growth of sporelings. We also assessed the effect of flow rates (1.5, 4, 10 cm s−1) and flow type (turbulent, laminar) on the growth of adult P. capillacea. Sporeling survival 48 h post-settlement was unaffected by flow type, and carpospores survived better than tetraspores on ropes. After four weeks, sporelings in raceways survived better on ropes than on glass slides, and sporelings derived from carpospores survived better on ropes than those from tetraspores. Sporelings grown in raceways were 5.8 times larger than those in the laboratory, but flow types had little effect within raceways. Seaweeds grown from carpospores grew 1.2 times larger than tetraspore in the raceways. Flow rate and type had little effect on the growth of adults, and their growth was slow possibly because of smothery by epiphytes. This study suggests P. capillacea spores are amenable to raceway culture, but adults do not fare as well in similar conditions.

Determining the Effect of Different Ecological Conditions on the Maturation of Rabbitfish (Siganus guttatus)

A study aimed at the rabbitfish Siganus guttatus (Bloch, 1787), the reproductive ability of one economically important marine and brackish fish in Giang lagoon systems and marine Asia. The future expectations of mariculture development were decided in Vietnam. The region had enough fingerlings for intensive culture and polyculture to contribute to environmental conservation and sustainability. There were 3 experiments in 3 different ecosystems for fish culture and maturity by feeding a commercial feed and finding suitable areas for the maturing period. The results showed that the growing fish kept in cages on the lagoon had the best growth and rate maturity, much higher than fish in cages of shrimp ponds and plastic bottom ponds, as showed a much bigger size of body, 610 g/head for females and 542 g/head for males, while other culture more 500/head, especially after 3 months of feeding, more than 20% matured for females, they reached more 50% at 6 months feeding. The length at first sexual maturity was 28.87 to 31.20 cm and 27.47 to 29.20 cm for females and males, respectively. The potential ova diameter is from 405 to 483 µm, P &lt; 0.05; the benefit for spawning, gonads maturity stages, with GSI (gonadal-somatic index), 3.03 to 4.53 were opportunities for the spawning season, ova diameter and fecundity and the gonadal-somatic index were differed significantly (P &lt; 0.05) males and females. This result showed the maximum (peak), and all fish can mature and get to spawning. In conclusion, different ecosystems impacted maturity and spawning during the moon season.

Evaluation of cannibalism during hatchery rearing of tiger muskellunge crosses

AbstractObjectiveJuvenile tiger muskellunge (Northern Pike Esox lucius × Muskellunge E. masquinongy) are cannibalistic, which can lead to a substantial reduction in yields within an intensive culture environment. Utah hatcheries have traditionally raised the female Northern Pike × male Muskellunge cross, and hatchery managers are reluctant to raise the female Muskellunge × male Northern Pike due to a perceived difference (increase) in cannibalism rates when rearing this cross.MethodsWe raised both crosses in replicated microcosms to evaluate the differential cannibalism between them. All rearing conditions were consistent among treatments and replicates. We evaluated weekly cannibalism using generalized linear regression models.ResultAfter 6 weeks, we found that the female Muskellunge × male Northern Pike cross offspring were significantly more cannibalistic than juveniles from the female Northern Pike × male Muskellunge cross, with total cannibalism across the 6‐week period estimated at 27% and 5.6%, respectively.ConclusionWe documented a previously unreported difference in tiger muskellunge cross cannibalism rates. Choosing the female Northern Pike × male Muskellunge cross could substantially increase survival of juvenile tiger muskellunge in aquaculture facilities.