Volume 73, 2021

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https://hdl.handle.net/10524/63746

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A comparison of the physiological responses to heat stress of juvenile and adult starry flounder (Platichthys stellatus)
(2021) Lee, Hyo B.; Yoon, Ji H.; Park, Jung Y.; Lee, Il Y.; Lim, Han K.
Water temperature is the most important factor in fish farming as changes in water temperature cause physiological stress in fish. There have been few studies on physiological responses to high temperatures, which vary with aging. This study investigated the responses of juvenile and adult Platichthys stellatus to heat stress. Plasma cortisol, glucose, lactate, and lysozyme levels, antioxidant enzyme activities, and expression of heat shock proteins 70 and 90 (HSP70 and HSP90) of P. stellatus were determined at water temperatures of 16, 20, 24, 28, and 30°C. As a result, it was confirmed that several plasma parameters of adult were significantly higher than that of juvenile under heat stress. Plasma cortisol and glucose levels of adult were increased than juvenile at 24 and 28°C. Plasma lactate level of adult were higher than that of juvenile at 28°C. Comparisons of survival and physiological changes showed that juveniles have better thermal tolerance, resulting in a higher cumulative survival rate. Moreover, the relationship between thermal tolerance and HSP gene expression revealed that expression of HSP70 and HSP90 was significantly upregulated at 28°C in both juvenile and adult fish, and HSP70 expression was significantly higher in juvenile fish than in adult fish. It is judged that the adult's HSP70 activity was lower than juvenile, so the demand for plasma parameters for heat response was relatively high, whereas juvenile's HSP70 activity increased at 24 and 28°C, indicating a relatively stable value of plasma parameters. These results indicate that the thermal tolerance of juvenile fish is greater than that of adult fish, based on the differences in plasma parameters and HSP expression. These findings improve our understanding of age-related changes in P. stellatus during thermal stress and may help guide the management of fish farms.
Characterization, functional analysis and antibacterial activities of theromacin from the Akoya pearl oyster Pinctada fucata
(2021) Guo, Hua-Yang; Liu, Bo; Yang, Jing-Wen; Jiang, Shi-Gui; Zhang, Dian-Chang
The Akoya Pearl oyster Pinctada fucata is distributed over the coastal area of South China and is the most popular farming shellfish for seawater pearl production. Antimicrobial peptides (AMPs) could inhibit or kill pathogenic microorganisms. Theromacin has been proven to be an antimicrobial peptide, which plays an essential role in the body's immune system. The AMP gene to be identiﬁed was encoding theromacin in the pearl oyster Pinctada fucata (PoAP). The full-length PoAP cDNA contains 522 bp and consists of a 5’-UTR of 6 bp, an unusually long 3’-UTR of 749 bp, and an open reading frame (ORF) of 375 bp that encodes a 124 amino acid peptide with a molecular weight of 13.67 kDa and the theoretical isoelectric point of 9.25. Homology analysis of the deduced amino acid sequence of the PoAP with other known theromacin sequences by MatGAT software revealed that the PoAP shared 29.0%-46.8% similarity to the other known theromacin sequences. Signal P-N program showed that PoAP contains 33 amino acid signal peptides and a mature peptide located at amino acids 34-124; the mature peptide contains 12 cysteine residues and 13 alkaline amino acid residues with a molecular weight of 13.67 kDa and the theoretical isoelectric point of 9.25. The tempered program suggests that PoAP is a membrane protein with one transmembrane helix between amino acids 13 and 34. The PoAP gene was linked into prokaryotic vector pET-32α, and the PoAP fusion protein with 31 kDa molecular mass was successfully expressed in Escherichia coli BL21. Using His-Bind Purification Kit Protocol purifies the antimicrobial peptides recombinant protein and compares the bacteriolysis effect on Gram-positive and Gram-negative bacteria using the purified protein. The results show that PoAP proteins had a bacteriolysis effect on the Gram-negative bacteria but on Gram-positive organisms. The antibacterial peptides theromacin seem to play a crucial antibacterial function in the immune responses of pearl oysters.
Expression analysis of three immune genes IL-8, IL-6 and IL-1β in the Japanese flounder (Paralichthys olivaceus)
(2021) Pan, Qiuli; Zhang, Feng; Liu, Yang; Zang, Lin; Wang, Xiuli; Qiu, Xuemei
Interleukin-8 (IL-8), Interleukin-6 (IL-6), and Interleukin-1β (IL-1β) are major immune-related genes that play important roles in the innate immune system of vertebrates. In this study, the expression levels of the three immune-related genes in eleven tissues of normal adult Japanese flounder (Paralichthys olivaceus) were examined using semi-quantitative RT-PCR at 13time points after challenge with Lipopolysaccharide (LPS). The results showed that the highest expression levels of the Japanese flounder IL-8 were detected at 12h in the spleen, 12h in the head kidney, and 24h in the liver after the challenge with LPS. Interestingly, the expression levels of IL-6 in the spleen and head kidney were highest at 48h. The liver had the highest expression level of IL-6 at 36h.The highest expression levels of IL-1β were detected at 3h in the spleen and 9h in the head kidney and liver. These results indicated that IL-8, IL-6, and IL-1β also played important roles in the immune response of the Japanese flounder at lower temperatures. The study provided a basis for further research on the immune mechanisms of IL-8, IL-6, IL-1β, and the production of recombinant IL-8, IL-6, or IL-1β used in Japanese flounder cultivation.
Effect of Power Pump and Nozzle Diameter Microbubble Generator to Increase Oxygen Concentration in Aquaculture
(2021) Taukhid, Imam; Trijuno, Dody D.; Karim, Muhammad Y.; Syah, Rachman; Makmur, Makmur
Various types of microbubble generators for use in aquaculture facilities for aeration. The aeration system is essential for high-density shrimp cultivation. However, there is a blockage in the microbubble generator aeration system, and generally, aeration at high densities requires considerable electrical power. In this study, modifications were made to various diameter nozzles and various pump power for microbubble generators. This research was conducted to determine the best microbubble by comparing the nozzle diameter and pump power. To achieve this goal, three diameter nozzles are combined with three different powers with an airflow rate of 2.5 LPM. The best combination of 32.5 mm nozzle diameter and 160-watt pump power. Produce bubbles ranging from 5.6 – 82 μm, with an increased oxygen concentration time of 60 minutes.
First report of Iridovirus (ISKNV) infection in Israeli mariculture gilthead sea bream (Sparus aurata) at the Mediterranean Sea
(2021) Smirnov, Margarita; Ofek, Tamir; Hershko, Hanna; Ron, Tetsuzan B.
Megalocytiviruses have caused mass mortalities in various farmed fish species, both edible and ornamental. Infectious spleen and kidney necrosis virus (ISKNV) belongs to this family of viruses and induces lethal diseases in cultured fish. Here, we publish the first report describing this epizootic virus affecting the sea bream (Sparus aurata) in the offshore mariculture farm located in the Mediterranean Sea in Israel. The infectious agent was diagnosed with histology analysis and was identified as ISKNV by PCR.
Entirely Farm-raised Snubnose Pompano (Trachinotus blochii) Under High Salinity in Saudi Arabia
(2021) Young, Benjamin C.; Alfaggeh, Riyadh H.
Snubnose pompano (Trachinotus blochii), a species of economic importance in the Red Sea region, has shown aquaculture potential in Saudi Arabia. The unique environment of the Red Sea causes aquaculture systems to operate under high salinity (42‰–45‰), but there is a lack of information regarding the culture of snubnose pompano in these conditions. This study estimated the survival, growth, and farming costs of snubnose pompano in two production systems: indoor and outdoor tanks. The experiments were performed in triplicate in 2020–2021, with 100 sub-adult fish per production system. The survival rate, growth performance, natural sexual maturation, and farming costs were determined. The results indicated that snubnose pompano culture is feasible under high salinity conditions using the indoor production system considering the significant differences in survival rate and growth performance, although the outdoor system had lower feed and labor costs. After 550 days of rearing, the sub-adult fish weighed more than 1,100–1,200 g, and both males and females had sexually mature gonads. These results show that spawning can be induced in high salinity (42‰) conditions. This study was the first to successfully farm-raise snubnose pompano in Saudi Arabia. Our results can thus be used as a reference for related research and aquaculture development in the Middle East region.
Variation of bacterial communities in black tiger shrimp (Penaeus monodon) with different growth performances
(2021) Li, Yundong; Zhou, Falin; Zhang, Wenwen; Yang, Qibin; Jiang, Song; Huang, Jianhua; Yang, Lishi; Jiang, Shigui
The intestinal bacteria of aquatic animals are closely related to their health and growth status. Penaeus monodon has become an important aquaculture species in the world because of its high nutritional value and market to demand. However, knowledge of bacterial communities on the growth phenotype of P. monodon is still limited. In this research, the bacterial community were comprehensively analyzed by using Miseq sequencing technology and bioinformatics. The results indicated that 29 phyla and 468 genera were identiﬁed by the taxonomic sequence. The data showed that the composition of microbial community was statistically different to fast-growing shrimps and slow-growing shrimps. There were significant differences in intestinal bacteria at the genus level. Lactococcus, Limnothrix, and Arthrospira had more abundance in the gut of fast-growing shrimps, which may promote the growth of P. monodon by affecting enzyme activities and improving immune response. Nautella, Shimia, Pseudoalteromonas, Aliiroseovarius, Albimonas, Tessaracoccus had more abundance in the gut of slow-growing shrimps. Nautella had the ability to express virulence by stimulated by environmental factors, thereby increasing the susceptibility to infection, which may have a negative impact on healthy growth of shrimps. Pseudoalteromonas, Aliiroseovarius and Shimia were related to the pathogenicity of shrimp, which may be an important factor affecting the growth of shrimp. Overall, this study demonstrates that the bacterial community associated with P. monodon was variation on different growth performance. These results can provide information on microbiome characteristics involved in the asynchronous growth of shrimp.
Lysine requirement of the spotted scat Scatophagus argus (Linaeus, 1766)
(2021) Nhu, Binh Mac; Truong, Dan Van; Thi, Thuy T. N.; Duy, Tram Q. N.; That, Chat T.; Serrano, Augusto E.
The study aimed to determine the lysine requirement of young spotted scat Scatophagus argus (Linaeus, 1776) (average body weight = 10.7 g). The feeding trial was conducted for 8 weeks with 5 experimental diets which were isonitrogenous, isocaloric and isolipidic (35% CP, 18.3 MJ·kg-1, containing lysine levels as treatments containing equal dietary protein (35%) and lipid levels (5%) in 3 replicates. The lysine content was from 1.22 g to 1.94 g lysine·kg-1 dry diet (35 to 55 g·kg-1 CP) with an average content of 0.18 g lysine·kg-1 dry diet per treatment. Results showed that the growth rate, feed conversion and protein efficiency ratios were significantly highest at lysine level of 1.58 g·kg dry diet-1(45 g·kg-1 CP). Fish survival was not influenced by dietary lysine. Lysine requirement level for juvenile scat was estimated using quadratic regression of the percent weight gain (PWG) and specific growth rate (SGR) against dietary lysine level to have a mean value of 1.64 g·kg dry diet-1 (4.75 g·kg-1 CP).
Reduction of Antibiotic-Resistant Bacterial Counts in a Mangrove-Riverine System in Capiz, Philippines - Preliminary Data
(2021) del Castillo, Carmelo S.; Añasco, Cherry P.; Tan, Valerie L.; Noblezada, Albert; Pagapulan, Mary J. B.; Valad-on, Eunice
The anthropogenic impact of effluents and indiscriminate use of antibiotics in aquaculture promotes the emergence and proliferation of antibiotic resistant (ABR) bacteria. Comparative total bacterial and ABR counts were determined from 3 locations of the Cadimahan river of Capiz province, Philippines. The upstream station showed lower total bacterial but higher ABR counts, which is the inverse of the downstream station which showed higher total bacterial but lower ABR counts. The ABR counts accounted for 0.0173%, 0.0043% and 0.0002% of the total bacterial counts for upstream, midstream, and downstream, respectively, showing a strong inverse correlation of -0.84 in the Pearson correlation coefficient. This result suggests a remediating effect potentially mediated by microbial dynamics in the Mangrove-riverine system.
Effects of date (Phoenix dactylifera L.) kernel essential oil on growth performance and innate immunoassay in rainbow trout (Oncorhynchus mykiss) juveniles
(2021) Gaballah, Mousa S.M.; Alkhunni, Saleh B.A.; GÜLTEPE, Nejdet
This study aimed to investigate the effects of date (Phoenix dactylifera L.) kernel essential oil on growth and development performance parameters as well as phagocytic activity, respiratory burst activity, superoxide dismutase, lysozyme activity, and myeloperoxidase activity from immune parameters of rainbow trout (Oncorhynchus mykiss). The nutritional study was performed for 45 days to assess the effect of three concentrations (0.5, 1, and 2 mL kg-1) of date kernel essential oil in rainbow trout. β-citronellol, an important compound in many respects, was found 31.70% in date kernel oil. It has been determined that the addition of date kernel essential oil to rainbow trout feed decreases the feed conversion rate, increases the percent body weight gain, and the specific growth rate. It was observed that phagocytic activity, respiratory burst activity, and myeloperoxidase activity values improved in date kernel essential oil added groups, however, superoxide dismutase and lysozyme activity values were not affected. Consequently, date kernel essential oil can be act as a growth promoter, increase innate immunity, and cheap feed additive for the rainbow trout juveniles.
Effects of substituting dietary fish meal with soybean meal isolate on growth performance, digestive enzyme activity, and intestinal morphology of spotted seabass (Lateolabrax maculatus)
(2021) Wang, Zhe; Yang, Linkun; Zhang, Chunxiao; Li, Xueshan; Wang, Ling; Lu, Kangle; Song, Kai
Soy protein isolate (SPI) is a promising plant protein source to replace fish meal (FM) in aquatic feeds. This study investigated the growth performance, digestive enzyme activity, and intestinal morphology of spotted seabass (Lateolabrax maculatus) fed diets with FM partially substituted by SPI. Three iso-nitrogenous and iso-lipidic diets were formulated to replace 0, 25, and 50% of FM with SPI, being abbreviated as FM, SPI25, and SPI50, respectively. Each diet was allocated to triplicates of fish for 8 weeks. The results indicated that the weight gain was gradually reduced with increasing dietary SPI levels, as did intestinal trypsin and lipase activities. However, these traits were not significantly decreased until 50% of FM was substituted by SPI. Furthermore, feed intake and lipid digestibility significantly decreased with dietary SPI inclusion. Moreover, replacing 50% of dietary FM with SPI significantly reduced the intestinal villus height and perimeter ratio, whereas these traits did not markedly differ between FM and SPI25 groups. In conclusion, this study indicated that up to 25% of dietary FM could be substituted with SPI without significantly affecting the growth, digestive enzyme activity, or intestinal morphology in spotted seabass.
Analysis of Some Immune Parameters in The Skin Mucus of Four Cultured Fish Species
(2021) Baba, Esin
The skin mucus layer and its components provide the first line of defense against fish pathogens. The skin mucus samples were taken from four species Nile tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss), Siberian sturgeon (Acipender baerii), and the European sea bass (Dicentrarchus labrax) for analyzing of some immune parameters. It is measured the activities of alkaline phosphatase, lysozyme, myeloperoxidase, bactericidal activity (against Aeromonas hydrophila), total protein and immunoglobulin concentration. The sea bass had highest level of lysozyme, myeloperoxidase, and bactericidal activities, and so were the total protein and immunoglobulin concentrations. The alkaline phosphatase activity in skin mucus measured in Nile tilapia as maximum level while the immune activity observed in sea bass among fish species. The skin mucus determined a more robust bactericidal activity against A. hydrophila fish pathogen in all fish species. The current study results presented preliminary information for better comprehension of the function of skin mucus as a key component in the different fish immune systems in aquaculture.
Substituting dietary fishmeal with soybean meal isolate influences hepatic lipid metabolism and gut microbiota in spotted seabass (Lateolabrax maculatus)
(2021) Wang, Zhe; Yang, Linkun; Zhang, Chunxiao; Wang, Ling; Lu, Kangle; Song, Kai
This study was conducted to investigate the effects of partial substitution of dietary fishmeal (FM) by soy protein isolate (SPI) on lipid metabolism and gut microbiota of spotted seabass. A diet containing 30% FM formed the basal diet (FM), and two SPI diets were formulated in which 25% (SPI25) and 50% (SPI50) of FM were replaced by SPI. Each diet was fed to triplicates of fish for 56 days. The results showed that replacing dietary FM with SPI reduced triglyceride and cholesterol contents in the liver and serum, and the hepatic lipid droplets area was also decreased by dietary SPI inclusion. Furthermore, replacement of dietary FM with SPI markedly down-regulated the mRNA expression of genes involved in lipogenesis (srebpc-1c, fas, acc1, hmgcr, pparγ and chrebp) and lipolysis (atgl, hsl, pparα, and cpt1). Moreover, high-throughput sequencing analyses of gut microbiota revealed that dietary SPI inclusion dramatically decreased the Firmicutes/Bacteroidetes ratio. Overall, this study indicated that replacing 25-50% of dietary FM with SPI could reduce lipid accumulation in serum and liver of spotted seabass, which was associated with the suppressed hepatic lipogenesis and the remodeled gut microbiota.
High prevalence of Aeromonas and Pseudomonas infections among cage cultured Pangas catfish from the reservoirs of Maharashtra, India
(2021) Rathinam, R. Bharathi; Banu, Husne; Ghode, Gajanan S.; Bhushan, Shashi; Bhuvaneswari, Rathi; Tripathi, Gayatri
Cage farming of Pangas catfish (Pangasionodon hypophthalmus) in small reservoirs is primarily profitable. Still, sustainability in terms of disease and environmental impact issues remains unsolved. In the present study, Pangas catfish from selected farms were screened for bacteria and parasites from 2017-18. In the present study, several Gram-negative bacterial species, including Edwardsiella tarda, Aeromonas hydrophila, A. veronii, Pseudomonas putida, Enterobacter cloacae, and Plesiomonas shigelloides, were isolated. A high prevalence of Aeromonas and Pseudomonas infections was noticed in cage farms. The most prevalent isolate was A. veronii (9 isolates), followed by P. aeruginosa and P. putida, revealing the presence of biotic stress. Furthermore, potential human pathogenic bacteria, particularly Klebsiella pneumoniae, P. aeruginosa, Acinetobacter baumannii, Citrobacter freundii, and Morganella morganii, were isolated. Histopathological analysis of the vital organs concluded the extent of damage caused due to the biotic stress in the cage culture system. The antibiotic sensitivity test implied resistance of bacteria for Sulphamethoxazole and Tetracycline. Some of them were resistant to multiple drugs, the risk for public health. Water temperature, dissolved oxygen, pH, Aeromonas, Pseudomonas, and Plesiomonas were identified by principal component analysis as significant abiotic and biotic stress factors. This information helps design predictive disease models.
Structure, proximate composition, nutrient dynamics and growth characteristics of Penaeus vannamei in indoor biofloc systems with three different salinities and carbon sources
(2021) Anand, Theivasigamani; Srinivasan, Arasan; Padmavathy, Pandurengan; Jawahar, Paulraj; Sampathkumar, J. Stephen
In the biofloc systems the continuous application of carbon sources led to the assimilation of nitrogenous nutrients and formation of heterotrophic bacterial biomass. The present experiment was conducted in 0.22m3 capacity tanks in the triplicate to find out the structure, proximate composition, nutrient dynamics and growth characteristics of Penaeus vannamei in indoor biofloc systems with three different salinities (35, 20 and 5ppt) and carbon sources (molasses, sugar and rice flour) with an estimated C:N ratio of 15:1. pre salinity acclimatized P. vannamei , specific pathogen free seeds (0.2±0.04g) were stocked @100 numbers per m3 and fed 4 times a day based on the % of body weight (from 22% to 2.5%) and reared for 10 weeks. The results revealed that the carbon application at different salinities significantly influenced the biofloc structure (Scanning Electron Microscopic images of biofloc 4000x) showed round and rod-shaped structures. Proximate composition: crude protein (p<0.001), ether extract (p<0.001) and crude fibre (p<0.05) showed significant difference between treatments. Similarly, elemental carbon composition (p<0.01), nitrogenous waste assimilation of TAN (p<0.01), nitrite (p<0.05), and nitrate (p<0.05) showed significant differences in the treatments vs. the control group. The variables also influenced the microbiota abundance {the metagenomics analysis of biofloc showed Bray-Curtis overall average dissimilarity index of 81%, and it varied from 49% to 100% between treatments & controls} and growth characteristics {average body weight (p<0.001) and survival rate (p<0.01) between treatments and controls} of P. vannamei indoor biofloc systems. Hence, the application of carbon sources at different salinities influenced the biofloc structure, proximate, elemental carbon composition, biofloc microbiota abundance, enhanced the nitrogenous waste assimilation and growth performance of P. vannamei in indoor biofloc systems.
Characterization and expression analysis of heat shock protein 90β from golden pompano (Trachinotus ovatus, Linnaeus 1758) in responses to stock density stress and Cryptocaryon irritans infection
(2021) Guo, Hua-Yang; Yang, Quan; Liu, Bo; Liu, Bao-Suo; Zhang, Nan; Guo, Liang; Zhu, Ke-Cheng; Zhang, Dianchang
Heat shock protein 90 family, a class highly conserved protein and important molecular chaperone and its plays a role in enhancing animal adaptability to environmental stress and improving immunity. In this study, a full-length HSP90β cDNA (ToHSP90β) sequence was identified from Trachinotus ovatus. The cDNA of ToHSP90β was 2648 base-pairs (bp) long and contained a 5′-terminal untranslated region of 130 bp, a 3′-terminal untranslated region of 334 bp, and the open reading frame length 2184 bp, which can encode 728 amino acids. The ToHSP90β has a heat shock protein 90 family signature. The ToHSP90β amino acid sequence has high homology with other fish HSP90β amino acids (92.5-99.17%) and contains five conserved signal regions and a structural feature of the cytoplasmic HSP90 family. Phylogenetic tree analysis indicated that ToHSP90β was most closely related to Seriola dumerili HSP90β. Tissues expression analysis showed that the ToHSP90β was expressed in all nine tissues of T. ovatus, and its expression was the highest in the intestine. The stocking density significantly affected the expression of ToHSP90β in the kidney and brain tissues, and its expression levels increased significantly with increasing stocking densities, indicating that it plays an important regulatory role in the process of T. ovatus’ chronic stress response. After Cryptocaryon irritans infection, the mRNA expression of ToHSP90β was signiﬁcantly increased in liver and kidney tissues, indicating that ToHSP90β would be involved in the immune regulatory response. This study was the first to analyze the expression pattern of HSP90β mRNA in T. ovatus tissues and their expression responses to stocking density stress and C. irritans infection. To provide a theoretical basis for further study of the function of fish HSP90 and its physiological mechanism in environmental stress and parasite infection.
Development and characterization of 20 microsatellite markers in spotted sea bass (Lateolabrax maculatus) and cross-amplification in related species
(2021) Fan, Sigang; Huang, Hao; Wang, Pengfei; Yan, Lulu; Zhao, Chao; Qiu, Gaofeng; Qiu, Lihua
The spotted sea bass (Lateolabrax maculatus) is an economically valuable cultured fish species in China. In this study, 20 novel polymorphic microsatellite loci of L. maculatus were isolated from genomic data and characterized using 40 wild individuals. The number of alleles and the effective number of alleles ranged from 2 to 12 (average of 5.1000) and from 1.180 to 8.000 (average of 3.3097). The observed and expected heterozygosities ranged from 0.083 to 0.875 (average of 0.4405) and from 0.153 to 0.875 (average of 0.5633), respectively. Deviation from the Hardy-Weinberg equilibrium was observed in 11 loci (P < 0.05). Polymorphism information content ranged from 0.141 to 0.862 (average of 0.5265) and most loci were heterozygous. Cross-amplification trials in two cryptic congeneric species, the largemouth bass, Micropterus salmoides, and the barramundi, Lates calcarifer, achieved successful amplification of 16 primers. The microsatellite markers developed in this study could be used for research on genetic breeding of L. maculatus and genetic relationships among tested taxa.
Effects of dietary compound acidifiers supplementation on growth performance and intestinal health of juvenile American eels (Anguilla rostrata) cultured in cement tanks
(2021) Zhang, Mingliang; Wang, Yue; Zhai, Shaowei
This experiment was conducted to investigate the effects of compound acidifiers (CAs) on the growth performance and intestinal health of juvenile American eels (Anguilla rostrata) cultured in cement tanks. Six cement tanks with similar fish size and weight (approximately 4 g/fish and 87 kg/tank) were randomly divided into control group and CAs group with three replicates each. The fish of two groups were fed commercial diet and commercial diet supplemented with 4 g/kg CAs, respectively. The trial period was 56 days. The dietary CAs supplementation significantly increased final fish weight, weight gain rate, specific growth rate and feed intake (P<0.05). There were no significant differences in feeding rate, feed efficiency, and survival rate between the control group and CAs group (P>0.05). Protease activity in intestine was increased significantly by CAs supplementation (P<0.05). Lipase activity and amylase activity were similar between control group and CAs group (P>0.05). CAs supplementation significantly increased the villi length and thickness of the intestinal muscular layer (P<0.05). Dietary CAs supplementation increased the richness and the diversity of intestinal microbiota. At the phylum level, the higher relative abundances of Proteobacteria, Actinobacteria and Bacteroidetes and the lower relative abundance of Firmicutes were observed in CAs group compared to the control group. At the genus level, dietary CAs supplementation significantly increased the relative abundances of Faecalitalea, Sphingomonas, Sutterella and Mycobacterium (P<0.05). In conclusion, the dietary 4 g/kg CAs supplementation might improve the growth performance and intestinal health of juvenile American eels cultured in cement tanks.
Status, Trends, and Prospects of the Channel Catfish Industry in China and the impact of the Covid-19 epidemic
(2021) Zhou, Zhen; Dai, Yun-Yun; Yuan, Yuan; He, Yan-Hui; Zhou, Jing
In 1984, the Fisheries Research Institute of Hubei Province first introduced channel catfish from the US to China. Since then, the production of China's channel catfish has undergone volatile changes. In 2003, as a substitute for Pangasius fillets from Vietnam, the export volume of channel catfish-processed products increased considerably. In recent years, the Chinese channel catfish industry has shifted from dependence on American and European markets to dominance in Chinese markets. It is expected that the continuing impact of the Covid-19 epidemic in China and the development of the global pandemic will significantly affect the channel catfish farming sector in China. This paper outlines China's channel catfish industry's development, markets, costs, and benefits and provides some suggestions for its development.
Effects of Photoperiod, Water temperature, and Exogenous Hormones on Spawning and Plasma gonadal Steroid in Starry Flounder, Platichthys stellatus
(2021) Hong, Beom S.; Lee, Hyo B.; Park, Jung Y.; Yoon, Ji H.; Lee, Il Y.; Lim, Han K.
The sexual maturation and spawning of teleosts are regulated by the external environment and the endocrine system. When the environmental conditions are artificially adjusted at a fish farm, the maturity and spawning of fish can be controlled. In this study, sexual maturation and spawning of the starry flounder, Platichthys stellatus, were artificially induced by adjusting the water temperature and photoperiod at a fish farm to accelerate the species’ natural spawning period. One experimental group acted as a control and was exposed to a natural photoperiod and natural water temperature (NPNT). In contrast, another experimental group was exposed to an adjusted environment consisting of a regulated photoperiod and temperature (RPRT). Daylight time was reduced by 10 minutes every 3 days from 13 hours to a duration of 8 hours. The water temperature was first reduced by 1oC every day, starting at 22oC and ending at 8oC, and then raised to 10oC until the spawning period. Both experimental groups were treated with gonadotropin-releasing hormone analog (GnRHa) pellets to induce ovulation. The results show that when the water temperature and photoperiod were artificially controlled, ovulation could be induced 97 days earlier than the natural spawning. Plasma testosterone levels of RPRT and NPNT tended to increase and then decrease 1–2 months before spawning, and plasma levels of 17α,20β-dihydroxy-4-pregnen-3-one increased 1–2 months before spawning. The concentration of estradiol-17β (E2) in plasma was not associated with spawning.

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