Abstract:Shandong is a major fishery province in China, which shoulders the critial mission of building the "blue granary". The high-quality development of the aquatic seed industry in Shandong Province is significant for ensuring the sustainable and diverse supply of aquatic products in China. Based on the results of references analysis and field investigation, this study systematically summarized the status quo of the aquatic seed industry in Shandong Province and then pointed out the drawbacks in overall design and planning, collection and preservation of germplasm resources, innovation and application of breeding technologies, cultivation of new varieties, and formation of leading enterprises. Based on that, we put forward the long-term goals, critical tasks, and suggestions for developing the seed industry of fish, shellfish, shrimps, crabs, sea cucumber, algae, and aquatic seed economy in Shandong Province. This study will provide references for the high-quality development of the aquatic seed industry in Shandong Province.

Abstract:The Chinese mitten crab (Eriocheir sinensis) is a vital freshwater economic crab in China. Its growth is limited by exoskeleton. In the process of growth and development, the exoskeleton must be shed periodically in order to complete its phased growth. A highly complex calcium regulation mechanism is needed in the molting cycle of E. sinensis. Sarco/endoplasmic reticulum Ca²⁺ATPase SERCA (SERCA) transports Ca²⁺ from the cytosol to the sarco/endoplasmic reticulum (SR/ER), where Ca²⁺ is mainly stored in cells. In order to improve the molecular mechanism of molting of E. sinensis, a series of functional analyses of the SERCA gene, the key factor of Ca²⁺ signal transduction, was carried out in this study. The experimental group prepared four kinds of culture water with different Ca²⁺ concentrations by adding analytical pure CaCl₂ (40 mg/L, 160 mg/L, 320 mg/L) to the fresh water, and the control group without CaCl₂. The relative expression of genes were tested using qRT-PCR method. The result showed that the relative expression of genes related to Ca²⁺ signal pathway SERCA, PMCA, RyR and NCX in Y-organs and gill tissues increased, the relative expression of MIH in eyestalks decreased. The concentration of Ca²⁺ and ecdysone in hemolymph increased tested using ELISA method. The results showed that high concentration of Ca²⁺ could promote the absorption of Ca²⁺ from the water environment and transport across cells to hemolymph through the joint regulation of SERCA, PMCA, RyR and NCX in the gills of E. sinensis, thus increasing the concentration of Ca²⁺ in the hemolymph. In Y-organs, the relative expression of genes related to the Ca²⁺ signal pathway was increased, and the Ca²⁺ signal was up-regulated, which was involved in the regulation of intracellular calcium homeostasis. Meanwhile, the MIH gene was down-regulated in the eyestalks. This series of reactions promoted the transformation of E. sinensis to the premolt stage, accompanied by an increase in the concentration of ecdysone in hemolymph. After injecting the ds RNA of SERCA gene to E. sinensis for 24 h, 48 h, 72 h and 96 h, the knock down efficiency of SERCA gene were 65.67 %, 55.5 %, 32.10 % and 15.43 %, respectively, which showed it could effectively knock down the expression of SERCA gene, meaning it can be used in the next experiment. After knocked down of SERCA gene by RNAi and no Ca²⁺ was added to the culture water, and knocked down SERCA gene in high calcium environment (320 mg/L of Ca²⁺ was added to the culture water), the relative expression of PMCA and NCX genes in Y-organs increased, while the relative expression of RyR gene decreased. The concentration of intracellular Ca²⁺ was tested using Fluo-3 AM probe and it was increased. It suggested that the SERCA gene played an important role in maintaining intracellular Ca²⁺ concentration and intracellular calcium homeostasis in E. sinensis. Continuous knock down of SERCA gene expression could significantly prolong (P < 0.05) the molting interval and decrease the weight gain rate and survival rate of E. sinensis. SERCA is the critial factor of Ca²⁺ signal transduction, which not only participates in the regulation of molting, but also plays an important role in many cellular functions, knock down of SERCA gene expression may cause intracellular calcium homeostasis imbalance, interfere with Ca²⁺ signal, and cause adverse effects on other physiological activities, thus reducing the survival rate of E. sinensis. Continuous knock down of the SERCA gene in a high calcium environment resulted in shorter molting interval but aggravated intracellular calcium disorder and decreased survival rate compared with continuous knock down of the SERCA gene group. The results of this experiment will provide an essential reference for the further study of the molting mechanism of E. sinensis. It suggests that SERCA gene plays an important role in molting of E. sinensis. The study will improve the molecular mechanism of molting of E. sinensis, provide basic reference for further study of the molting mechanism and genetic improvement of E. sinensis, and provide theoretical support in the exploration of scientific culture and improving culture efficiency.

Abstract:As the center of cellular energy regulation in eukaryotic cells, AMPK senses and maintains energy balance in peripheral tissues by modulating various metabolic pathways. It plays a vital role in regulating the body's physiological activities and maintaining the body's homeostasis. Although the AMPK gene family has been extensively studied, systematic identification and analysis of the AMPK gene family in Patinopecten yessoensis are still lacking. In order to understand the characteristics, evolution and biological function of the AMPK gene family in P. yessoensis, we conducted genome-wide identification and functional and evolutionary analysis of the AMPK gene family in P. yessoensis. We also investigated the expression profiling of the AMPK gene family under heat stress. The results showed that three AMPK genes were identified in the genome of P. yessoensis including PyAMPKα, PyAMPKβ and PyAMPKγ, which were necessary subunits to form the AMPK complex. Spatiotemporal expression profiling suggested that three AMPK genes have relatively high expression level before the D-shaped larval stage. The PyAMPKα, PyAMPKβ and PyAMPKγ genes exhibited the highest expression level at the fertilized egg stage, blastocyst stage, and the fertilized egg and 2-8 cell stage, respectively. PyAMPK had distinct expression patterns in various adult tissues with the highest expression in kidney, followed by gill. Furthermore, we found the expression levels of all three AMPK genes in the kidney and gill increased first and then decreased over time in the group under the heat stress. Our study results showed that the AMPK genes not only regulated energy balance at early embryo development in scallops, but also participated in the response to heat stress. This study would benefit for understanding the function and evolution of AMPK gene in molluscs, and laid the foundation for further research on the regulation mechanism in response to heat stress in molluscs.

Abstract:Like other macroalgae, Saccharina japonica also has CO₂-concentrating mechanism (CCM) to realize high photosynthesis efficiency as well as elevated biomass. Phosphoenolpyruvate carboxylase (PEPC) in the cytoplasm was suggested to be an essential component of CCM. However, there was no report about cytosolic PEPC of S. japonica. In this study, the full length cDNA sequence (SjPEPC) of a PEPC gene, which might be located in cytoplasm,was screened from the full-length transcriptome of this kelp and was identified by RT-PCR. The full-length cDNA sequence of SjPEPC was 3 503 bp in length, consisting of a ORF of 2 850 bp, a 5′-UTR of 50 bp, and a 3′-UTR of 603 bp. It encoded a protein of 949 amino acids with a molecular weight of 104.91 ku, and a pI of 7.31. Multi-sequence alignment showed functional sites of PEPC were highly conserved in the selected species. Both phylogenetic analysis and sequence characterization showed that SjPEPC was a bacterial-type PEPC. pET32a-SjPEPC was constructed for expressing the recombinant SjPEPC harbouring all the enzyme active sites. After being induced by IPTG and purified, rSjPEPC with molecular weight of 86.3 ku was obtained. Enzyme activity assay results showed that rSjPEPC could catalyze the carboxylation of PEP, and the specific activity was (9.37±0.46) U/mg prot. These findings provide molecular and biochemical data for analysis the role of cytosolic PEPC in the storage of inorganic carbon in S. japonica, and furtherly for analysis CCM of this kelp.

Abstract:The Ruditapes philippinarum mainly inhabits estuaries, inner bays and coastal mudflat. Affected by tides, rainfall and seasons, the dissolved oxygen in their living environment is prone to change, which will affect their growth, survival and metabolism.The gills of bivalves are both respiratory organs and feeding organs used for filtering food. In order to investigate the effect of dissolved oxygen changes on the gill tissue structure of R. philippinarum and provide parameters for their aquaculture management, we designed three modes of dissolved oxygen changes, namely, continuous maintenance of regular dissolved oxygen C treatment, regular dissolved oxygen-rapid hypoxia for 24 h-rapid reoxygenation for 4 h AHR treatment, and regular dissolved oxygen-slow hypoxia for 48 h-slow reoxygenation for 8 h CHR treatment. Then tissue sections and immunohistochemstry methods were used to analyze the effect of dissolved oxygen changes on the gill tissue structure. The results of tissue sectioning showed that dissolved oxygen changes would affect the morphology and structure of gill tissue in R. philippinarum. Hypoxia caused gill filaments to widen, surface epithelial cells to damage, cilia to fall off, the sponge like blood cavity tissue to become loose, gill lumen gaps to become larger, and there were cell fragments inside. Hypoxia reoxygenation significantly changed the morphology of the gill flap, and the damage to the tissue cells of the outer gill flap was more severe than that of the inner gill flap. Slow hypoxia for 48 h and slow reoxygenation for 8 h caused more severe damage to the gill tissue structure than quick hypoxia for 24 h and quick reoxygenation for 4 h. The immunohistochemical results showed that both rapid hypoxia for 24 h and slow hypoxia for 48 h increase the ROS level in the gill tissue, while reoxygenation only reduced the ROS level a little in the gill tissue. There was no significant repair effect on the damage caused by hypoxia in a short period of time. The gill tissue cells damaged by slow hypoxia for 48 h and reoxygenation for 8 h were numerous and diffuse, with unclear nuclear cytoplasmic boundaries, the degree of damage to gill tissue cells was higher than that of rapid hypoxia for 24 h and reoxygenation for 4 h. In summary, this experiment found that both slow hypoxia for 48 h and rapid hypoxia for 24 h could cause damage to the cellular structure of the gill tissue. The damage to reoxygenated tissue cells could not be repaired in a short period of time. Slow hypoxia for 48 h caused more severe damage to gill tissue structure than fast hypoxia for 24 h. The tissue cell damage continues to worsen even after 8 hours of slow reoxygenation. The results of this study suggested that the management of R. philippinarum farming need to consider the stable control of dissolved oxygen, and efforts should be made to avoid changes in dissolved oxygen, especially the damage to the gill tissue of clams caused by long-term chronic hypoxia stress. This study provides parameters for dissolved oxygen control in the process of R. philippinarum aquaculture.

Abstract:The skipjack tuna purse seine fishery in the West and Central Pacific Ocean is a typical kind of distant water fishery. The selection of host states decided by pelagic fisheries companies is influenced by various aspects such as resources factors, economic factors and social factors. To enhance economic performance of pelagic fisheries companies, taking the 5 host states of Micronesia, Papua New Guinea, Marshall Islands, Nauru and Kiribati as subjects, and based on previous studies about resources distribution and fisheries risks, an indicator system for host state selection in skipjack tuna purse seine fishery was built under Analytic Hierarchy Process (AHP). Aiming at maximizing the profit, the system consisted of 3 first-level indicators which were resources situation, economic costs and fishery risk as well as 8 second-level indicators. Based on statistical data from Western and Central Pacific Fisheries Commission (WCPFC) and survey data from pelagic fisheries companies from 2017 to 2020, taking the entry-fishing effectiveness of 5 entry-fishing countries as an example to verify the indicator system. Results showed that Nauru was the most suitable entry-fishing country with stable scores over 65 among 5 years, while Marshall Islands was the worst with scores lower than 65. By the way, the scores of Micronesia, Papua New Guinea and Kiribati were unstable and slightly lower than that of Nauru. Among the two-level indicators, resource situation played a vital role and the economic costs was in the next place, while fisheries risks had the most minimal impact. The weights of first-level indictors in descending order were resource situation (0.479), economic costs (0.372), fishery risks (0.149). The weights of second-level indictors in descending order were resource abundance (0.265), vessel day access fee (0.171), time for searching (0.151), percent of suitable habitat (0.148), social stability (0.078), foreign relations of the state (0.071), percent of species with high commercial value (0.066) and time for transferring (0.050).Our study systematacially summarized the current status of Chinese Katsuwonus pelamis purse seine fishery and provided references for pelagic fisheries companies.

Abstract:Pacific oyster (Crassostrea gigas) is a widely aquaculture shellfish in China. Managing the coastal aquaculture area of C. gigas can increase the yield and reduce the losses caused by the environment in Shandong. With the development of remote sensing and artificial intelligence, convenient conditions are provided for evaluating suitability for aquaculture. The autumn-winter fattening aquaculture is an efficient aquaculture method for Pacific oysters. In this study, based on Dynamic Energy Budget (DEB) theory, sea surface temperature, chlorophyll-a and total suspended sediment data obtained by satellites and sea surface height reanalysis data, were used to construct an evaluation model for C. gigas suitability assessment in Shandong Peninsula. The results showed regional differences on the suitability index of fattening aquaculture in Shandong Peninsula, and the overall suitability trend was southern coastal area > northern coastal area > eastern coastal area > western coastal area. The most suitable aquaculture area in the southern coastal area was 9.1%, mainly in Rushan coastal. Several area in the Yellow River mouth area were unsuitable aquaculture area, accounting for as much as 30.5% of the area. The most suitable area of C. gigas fattening aquaculture in Shandong costal area was 38.2% in 2017 and 57.9% in 2019, much more than those of other years. The autumn-winter fattening aquaculture in Shandong for C. gigas was better located in areas with less turbidity, higher chlorophyll-a concentrations, warmer temperatures and fewer waves. The Yellow River estuary was not suitable for the autumn-winter fattening aquaculture due to the high turbidity. The northern and northeastern coastal area of Shandong, such as the northern part of Yantai City and the eastern part of Rongcheng City, were suitable for the fattening aquaculture due to the abundance of Chl.a and clarity of water. In the southern coastal area of the Shandong, such as the southern part of Qingdao City and the southern part of Lushan City, SST was warmer in autumn and winter, allowing oysters to continue to grow and develop, which was ideal for fattening. The results of this study can provide effective quantification and scientific basis for C. gigas aquaculture suitability assessment in Shandong Peninsula.

Abstract:The niche and interspecific relationships between Sepiella japonica and major nekton in the waters of the Zhongjieshan Islands were analyzed by niche breadth, niche overlap and association coefficient (AC) to explore the niche of S. japonica in the ecosystem, according to the survey data of fishery resources in the Zhongjieshan Islands sea area of four voyages in spring (April) and autumn (October) from 2020 to 2021. The results showed that 21 major nektons in spring and 14 in autumn. The niche breadth values of S. japonica in different seasons were quite different. S. japonica belonged to a wide niche in spring and a middle niche in autumn. In spring, the niche overlap between S. japonica and major nekton was low. The species pairs with O_ik≥0.5 accounted for only 14.29% of the total. In autumn, the niche overlap between S. japonica and major nekton was high. The species pairs with O_ik≥0.5 accounted for 50% of the total. AC analysis showed that the proportion of species pairs with positive interspecific association (AC≥0) between S. japonica and major nekton species was higher, among them, 19.05% of the 21 species pairs in spring had significant positive associations. A total of 14 species pairs in autumn, 35.71% had significantly positive associations. Research showed that the resource utilization ability, environmental adaptability and interspecific association of major nekton species were different in different life history stages of S. japonica. Based on the niche perspective, the resource decline mechanism of S. japonica was further explored, which could provide ecological basis for the protection and restoration of S. japonica habitat.

Abstract:The coast of Zhejiang has the most extensive fishing grounds in China and is rich in fish resources. Juvenile Engraulis japonicus is one of the key fish species in the area. However, due to over fishing and other human factors, which resources are less than they used to be. The Ministry of Agriculture and Rural Affairs approved juvenile E. japonicus fishery along the coast of Zhejiang in 2018 to achieve a sustainable harvest of this species juvenile. Meanwhile, there were no studies report using DNA barcoding to identify species of the fishery presently. To comprehensively understand the bycatch species of juvenile anchovy fishery and investigate the effectiveness of mitochondrial cytochrome oxidase subunit I (CO Ⅰ) gene in the identification of fish, this study adopted the method of DNA barcode-assisted morphological classification, taking 192 juvenile fishes from the by-catch of juvenile E. japonicus fishery. Finally, we identified 48 species, belonging to 46 genera of 2 classes 11 orders 36 families, of which 46 species were identified to the level of species, 2 to the level of genera, and 11 species of morphology misidentifies were successfully identified. The average length of 152 CO I sequences was 654 bp (634-656 bp), and conserved sites accounted for 47.21%, informative sites accounted for 45.25% and variable sites accounted for 51.89%. The content of C+G (47.66%) was significantly lower than that of A+T (52.34%), showing at AT bias, and the highest AT content was found at the site 3. The average interspecific genetic distance (0.252 3) was 74 times higher than the average intraspecific genetic distance (0.003 4). The largest genetic distance between genera was between Salanx and Pampus (0.339 5), and the smallest was between Trachurus and Alectis (0.119 7). The largest genetic distance between the families was between Salangidae and Stromateidae (0.339 5), and the smallest was between Atherinidae and Carangidae (0.192 1). The largest genetic distance was between Perciformes and Osmeriformes (0.276 2), and the smallest was between Scorpaeniformes and Atheriniformes (0.212 2). The ABGD analysis resulted in 48 OTUs, consistent with the morphological classification. The phylogenetic tree was constructed based on CO Ⅰ gene, and individuals of the same species could be clustered in the same branch. The species could be effectively distinguished, but the clustering relationships at the family and order levels were not clear. The DNA barcoding identification results were basically consistent with the morphological identification results. The above results indicated that DNA barcoding could be used as an effective method of identification of juvenile E. japonicus fishery in Zhejiang coast, which made up for the limitations and shortcomings of traditional morphological identification methods. The findings of this study can lay the foundation for the study of fish diversity and spawning migration along the Zhejiang coast, as well as provide a scientific basis for the sustainable development and utilization of juvenile Engraulis japonicus fishery.

Abstract:The Pelteobagrus vachelli and Leiocassis longirostris, belong to the order Siluriformes and family Bagridae, respectively fall under the genus Pelteobagrus and Leiocassis. Their interspecific hybrid offspring exhibit superior growth performance, suggesting significant production potential. As the hybrid offspring of P. vachelli and L. longirostris share similar morphological features with their parents, confusion may arise in production. DNA molecular markers can be used to accurately and rapidly distinguish species, and are commonly used for species identification. In this study, based on the published genomic data of P. vachelli and L. longirostris, comparative genomic analysis revealed a close evolutionary relationship between the two species. The estimated divergence time was about 3.7 million years ago. Moreover, through chromosome sequence synteny analysis, it was found that both species had 26 pairs of chromosomes. These chromosomes corresponded one-to-one, with no observed chromosomal fusions, only intra-chromosomal rearrangements. Based on these results, a 391 bp INDEL was identified in the patj gene sequence in the two fish species. Using this differential fragment, we designed the primer PVLL. This primer only amplified a 339 bp band in P. vachelli and a 730 bp band in L. longirostris, while in the hybrid species, it amplified both 339 bp and 730 bp bands. The difference in the amplified bands could be used to distinguish the three species, regardless of gender accurately . We further verified the validity of the primers in different populations. Accordingly, our study provides a theoretical basis for hybrid breeding between P. vachelli and L. longirostris through comparative genomic analysis. Furthermore, we developed a molecular marker that could efficiently and accurately identify P. vachelli, L. longirostris, and their interspecific hybrids, which will greatly improve the efficiency of hybrid breeding production.

Abstract:Antarctic krill (Euphausia superba) is the keystone species in the Antarctic marine ecosystem, and is also the marine protein source that left for human beings. E. superba is creatures that inherently form schools and display intricate social interactions. It is also known to engage in both vertical and horizontal movements in its natural habitat. The social dynamics within these schools are crucial to understanding various biological aspects of E. superba. Consequently, researches into its behavior are essential for comprehensive grasp of krill biology. The effect of visible light color on the aggregation behavior of E. superba was investigated through in-situ aquaria observation on the sea. Understanding the characteristics of the distance between individuals and their swimming angles within schools will help understand the size of schools in the field and improve the accuracy of the target strength (TS) model in acoustic estimate of this species. The krill school images were synchronously acquired by an optical stereo camera in this study. The high-precision automatic measurement of the geometric information of the key feature points of the krill individuals was completed with the help of photogrammetry technology, then obtained the individual distances and swimming angle in the schools under different visible light colors from blue (short-wave) to red (long-wave). Research had found that blue light had a better positive phototaxis to krill compared with long-wavelength red light. The absolute individual spacing of krill schools was (14.51±9.71) cm, and the relative individual spacing was (2.84±1.51) BL. The lighting conditions affected the distance between individuals in the krill schools, and there were significant differences in distance and swimming angle between individuals in the krill schools between short-wavelength blue light and long-wavelength red light. The swimming angle of E. superba under different light colors was (46.08±35.50) ° and concentrated around 60°. There was no significant difference in swimming angle between different light colors. This study helps to understand the characteristics of krill schools in autumn and winter seasons, and provides scientific references for the input parameters of the TS model for krill resource evaluation, in order to improve the evaluation accuracy of the model.

Abstract:The aquaculture of Procambarus clarkii has developed rapidly nationwide in recent years. According to statistics, the production of P. clarkii in 2021 reached 2 633 600 tons, become the most highly-produced freshwater crustaceans in China. However, limited knowledge about intensive breeding of P. clarkii seedlings has hindered its sustainable development. Artificial incubation may be an effective way to realize intensive breeding of P. clarkii seedlings. The mortality, hatching rate and embryo development of P. clarkii embryos were compared between in vitro incubation mode and maternal incubation mode to evaluate the feasibility of in vitro incubation of P. clarkii embryos and explore its artificial intensive incubation techniques. The results showed that the mortality of embryos at different incubation periods (2-4 days, 5-7 days, 8-10 days, 11-13 days of the experiment) were significantly different. Embryos mortality in the prepared hatching stage (11-13 days of the experiment) was significantly higher than that in 2-4 days and 8-10 days, but there were no significant differences in total embryos mortality between the two incubation treatments. At the same measurement time, the developmental stages of embryos of two incubation treatments were similar and there were no embryo morphological abnormalities. However, embryos hatched under in vitro incubation were susceptible to mycelial attachment, and the dead embryos of in vitro incubation were all infected by the mycelium. Two incubation treatments appeared the first instar larvae at the same time. The hatching rate of embryos of in vitro incubation was significantly lower than that of maternal incubation. But a higher hatching rate (76.91%±4.62%) of embryos under in vitro incubation was obtained. The study indicated that the feasibility of P. clarkii embryos under in vitro incubation was good. The main problem of embryos under in vitro incubation was the embryonic death due to the oomycete infection. In order to reduce the mortality of embryos under in vitro incubation, gradient anti-oomycete could be carried out.

Abstract:To investigate the effects of different oligosaccharides on the formation of biofloc and the structural characteristics of biofloc flora. Using glucose (GLU) as control, xylo-oligosaccharides (XOS), fructooligosaccharides (FOS), mannan-oligosaccharides (MOS), soybean oligosaccharides (SBOS), and maltose oligosaccharides (MTOS) were used as carbon sources to culture biofloc, ammonium chloride was used as nitrogen source and C/N was 15. The results showed that suspended particulate matter content and biofloc volume in the SBOS group were significantly increased (P<0.05) compared with other groups, and there were no significant differences between other oligosaccharide groups and the control group (P>0.05). Ammonia nitrogen gradually decreased and then stabilized. Compared with the control group and other experimental groups, the level of ammonia nitrogen in the SBOS group was significantly decreased (P<0.05). Except for the FOS group, the ability to reduce ammonia nitrogen in other experimental groups was higher than that in the control group. There was no significant difference in nitrite nitrogen degradation (P>0.05). Nitrate nitrogen showed a trend of decrease first and then increased, and the accumulation of nitrate nitrogen was decreased in all groups except the XOS group, and the accumulation of nitrate nitrogen was significantly decreased in the SBOS group and MTOS group (P<0.05). Compared with the control group, the abundance of biofloc and microbial diversity index was significantly decreased in the XOS group (P<0.05). From the analysis of phyla level, proteobacteria had the highest abundance in all experimental groups. Compared with the control group, proteobacteria and Proteobacteria in oligosaccharide groups were improved, and the abundance of Proteobacteria and Bacteroidetes in the FOS group was significantly increased (P<0.05). Regarding subordinate level, the proportion of Bdellovibrio decreased in the experimental group compared with the control group (P>0.05). Compared with the control group and other experimental groups, the FOS group significantly increased the abundance of unclassified_f_Rhodobacteraceae and significantly decreased the abundance of unclassified_f_Rhodobacteraceae and norank_f_Enterobacteriaceae (P<0.05). The results show that the biofloc constructed by oligosaccharide as carbon source can improve water quality, optimize bacterial community structure, increase the number of beneficial bacteria, and reduce the number of harmful bacteria. This study provides some theoretical basis for applying of oligosaccharides as carbon source in biofloc.

Abstract:As one of the most essential nutrients in life activities, protein plays a vital role in maintaining the good growth traits and health status of aquatic animals. Rice field culture is the one of the leading aquaculture pattern of Procambarus clarkii in China, which accounts for more than 80% of the annual production. Therefore, we should pay more attention to the protein requirements of P. clarkii farming in the rice field. In order to assess the optimal dietary protein requirement of juvenile P. clarkii farming in the rice field, six isoenergetic and isolipid diets were formulated to contain graded levels of 28%, 31%, 34%, 37%, 40% and 43% crude protein (described as Diet 28-Diet 43 group). Each diet was assigned to a triplicate of 20 experimental crayfish with an average initial body weight of (8.59±0.05) g for eight weeks. At the end of feeding trial, growth performance, muscle composition, hemolymph biochemical indexes, activities of digestive enzyme in intestine, antioxidant enzyme activities and non-specific immunity enzyme activity were measured. Our results showed that: ① The final body weight (FBW), weight gain rate (WGR) and specific growth (SGR) increased at first and then decreased. The meat yield (MY) increased with increasing protein level. ② The dietary protein levels did not significantly affect the muscle moisture, ash and lipid contents. The protein content of the muscle gradually increased as dietary protein level increasing, and then tended to decrease, and was highest in Diet 40 group. ③ The dietary protein level did not significantly affect the content of hemolymph total protein (TP), albumin (ALB), globulin (GLB), glucose (GLU), total cholesterol (TCHO) trended to decrease as dietary lipid level increased. Alanine aminotransferase (ALT) activity and aspartate aminotransferase (AST) activity in hemolymph significantly increased as dietary protein level increasing, both of them in Diet 43 group was highest. ④ The dietary protein level significantly affected the activities of intestine tryptaese and lipase, but not amylase activities. ⑤ Dietary protein also significantly induced the activities of the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), peroxidase (POD), lysozyme (LZM), acid phosphatase (ACP) and total antioxidant capacity (T-AOC), but the contents of malondialdehyde (MDA) was significantly induced. ⑥With dietary protein levels increasing, the expressions of molting-related genes (ecr, chitinase) and genes related immune (hsp70, tlrs, lzm) were firstly significantly increased and then decreased. However, dietary protein level did not significantly affect genes related to protein metabolism (eif4e, s6k1, 4e-bp1). Based on the WGR, broken-line analysis showed that dietary protein requirements of P. clarkii were 40.35% in the present study. In conclusion, under the present experimental conditions and in combination with other factors, the appropriate feed protein level was 40.35%. This study provided a theoretical basis for the development of dedicated feed for P. clarkii farming in the rice field.

Abstract:Ichthyophthirius multifiliis is the causative agent of “white spot” disease, which affects numerous freshwater fish and causes severe economic losses to worldwide aquaculture. The disease of I. multifiliis infection could develop very fast, and there are few practical measures to treat this heavy infection. To overcome the shortcomings of existing methods, for detecting I. multifiliis in the early stage and environmental samples, such as low sensitivity of visual diagnosis with microscope and low specificity of PCR methods developed in the previous studies, here we developed and validated novel PCR assays. In this study, a pair of primers (qIchF 5′-TTCTGCCCGTACTTTAGTTACC-3′ and qIchR 5′-TGGTTGTACTAACACCTGCAA-3′) were designed and screened to target the mitochondrial COⅠ gene of I. multifiliis. The length of the amplified product is 131 bp. After PCR programme optimization, specificity and sensitivity verification, clinical and environmental samples detection and analysis, standard PCR and real-time PCR assays were established, respectively. The standard PCR was incubated at 95 °C for 3 min; 35 cycles of denaturation at 95 °C for 15 s, annealing at 51 °C for 15 s, and extension at 72 °C for 10 s; and final extension at 72 °C for 5 min. For real-time PCR was incubated at 95 °C for 30 s; 40 cycles of denaturation at 95 °C for 10 s, annealing and extension at 60 °C for 30 s. The results showed that the primers obtained in this study had high amplification specificity for I. multifiliis. Ciliates Paramecium sp., Tetrahymena sp., and Balantidium sp. were not amplified, nor were common farmed fish hosts Carassius auratus gibelio, grass carp (Ctenopharyngodon idella), Nile tilapia (Oreochromis niloticus), and Megalobrama amblycephala. Amplification specificity and sensitivity were better than existing methods. The limit of detection for standard PCR was 2.67 theronts/μL, while real-time PCR could be detected at 0.02 theront/μL. Among them, the detection sensitivity of real-time PCR was higher than that of standard PCR. In the detection application of clinical samples and environmental water samples, the two PCR assays showed high consistency, and could effectively detect the latently infected fish and I. multifiliis in the pond water samples. Therefore, the assays developed in this study were suitable tools for early diagnosis and pathogen monitoring of I. multifiliis in freshwater aquaculture.

Abstract:Since the industrial revolution, the concentration of greenhouse gases in the atmosphere has risen rapidly due to human activities, which has seriously affected the global climate. The development of blue carbon industry has become an essential measure for people to cope with climate change. Cultivated seaweeds carbon sinks are an important component of blue carbon. Based on the data of seaweeds cultivation in eight coastal provinces of China, this research calculates the total economic value of the carbon sink of the cultivated seaweeds, and analyzes its spatiotemporal differentiation characteristics. The LMDI index decomposition method was used to analyze the influencing factors of the total economic value of carbon sink of cultivated seaweeds in China, which provided a reference for the reasonable calculation and evaluation of the economic value of carbon sink of cultivated seaweeds. The results showed that the carbon sink and total economic value of cultivated seaweeds in China showed an overall upward trend from 2009 to 2021,which reached 0.87 million tons and 48.8 billion CNY in 2021, respectively. The carbon sink of different seaweeds from high to low were Saccharina japonica, Gracilaria spp., Porphyra sensu lato, Undaria pinnatifida, and others (Sargassum fusiforme, Eucheuma muricatum, Gelidium amansii, and Ulva prolifera). The carbon removal capacities per unit area from high to low were S. japonica, G. spp., U. pinnatifida, others (S. fusiforme, E. muricatum, G. amansii, and U. prolifera) and Porphyra sensu lato. The total economic value of cultivated seaweeds carbon sinks in Fujian, Shandong, and Liaoning provinces were relatively high, while in other provinces those were relatively low. The culture efficiency effect (EFE) and culture area effect (AE) had a strong driving effect on the total economic value of carbon sinks in cultivated seaweeds. Research had found that the carbon sink potential of cultivated seaweeds in China must be addressed and could create huge economic benefits. The total economic value of cultivated seaweeds could be improved by adjusting the cultivation species and structure reasonably. Suggestions were proposed from the government, the scientific research unites, the industry practitioners and the public. Efforts should be made to enhance the function and value of fishery carbon sink, especially the cultivated seaweeds industries, to promote the high quality development of the fishery industry that contribute to mitigating global climate change, and realize the grand goal of " carbon-peaking and carbon neutrality".