Abstract:Hatchery-reared aquatic organisms usually have morphological and physiological differences compared to their wild conspecifics, which may have negative consequences the production of the juveniles under hatchery rearing conditions. To optimize the artificial breeding technologies of Sepiella japonica, we compared the morphology, biochemical composition and embryonic development between wild and hatchery-reared S. japonica. Furthermore, we also explored the effect of light cycle and capsule layer peeling on the embryonic development of S. japonica. The results showed that there were significant differences in morphological characteristics and biochemical components between wild and hatchery-reared S. japonica. The body sizes at maturity were much bigger in wild S. japonica than their hatchery-reared conspecifics. The lipid contents in muscle and liver of wild S. japonica were significantly lower than those of hatchery-reared. The protein contents in the ovary of wild S. japonica were significantly higher than those of hatchery-reared. The hatching rate of the black eggs spawned by the hatchery-reared cuttlefish was the highest when eggs were exposed to a 12∶12-hours light∶dark cycle. The hatching rate of the white eggs spawned by the hatchery-reared cuttlefish was the highest when eggs were exposed to the 24 hours dark cycle and 24 hours light cycle. The hatching rate of the black eggs spawned by the wild cuttlefish was the highest when eggs were exposed to the 24 hours dark cycle and 12∶12-hours light∶dark cycle. With the increasing light duration, the hatching period of fertilized eggs showed a tendency that it first increased and then decreased, which indicated that light cycle was an important factor for the development of embryo. With egg capsule layer peeling, the fertilized eggs from hatchery-reared S. japonica showed a significant decreased hatching rate, and the hatching time showed a decreasing tendency. To improve the hatching rate of the fertilized eggs and the survival rate of hatchlings, it is important to add sufficient number of wild brood-stock into productive group during artificial breeding and seedling production programs. Moreover, low light intensity should be implemented during the incubation of the fertilized eggs, which may improve the hatching rate and the survival rate of hatchlings. This study could provide useful information for the optimization of artificial breeding technology of S. japonica.

Abstract:To improve the germplasm resources of C. semilaevis (Cynoglossus semilaevis), a four-generation consecutive family selection was carried out for fast growth and Vibrio harveyi resistance. Starting from the third generation, we calculated the genomic estimated breeding value (GEBV) of V. harveyi resistance in C. semilaevis through the genomic best linear unbiased prediction and considered the families with high GEBV and infection survival rates as the superior disease-resistant family. In third-generation selection, we obtained 12 superior families. Their average infection survival rate (85.4%) and average GEBV (1.13) were higher than those of the control group (52.2%; 0.27). In fourth-generation selection, 5 families were selected as the superior disease-resistant families, and their average infection survival rate and average GEBV were 71.5% and 0.24, respectively. However, those of the control group were 30.1% and 0.03. After the four-generation consecutive selection, we cultivated the first new variety of C. semilaevis in China using the superior families with disease resistance and fast growth. Compared with the unimproved C. semilaevis population, the new variety “Tayou No.1” had 30.9% increase of survival rate after V. harveyi challenging, the body weight at 18-month-old increased by an average of 17.7%, and the survival rate in rearing improved 15.7% on average. The successful cultivation of C. semilaevis "Tayou No. 1" has added a good variety to the aquaculture breeding industry, promoted the development of the molecular breeding technology of C. semilaevis, and laid a foundation for the application of genomic selection in the aquatic breeding.

Abstract:Global marine fishery resources have shown a remarkable declining trend due to overfishing, climate change, environmental pollution and habitat destruction in recent decades. As a promising solution to the current challenge, fisheries stock enhancement is believed to be an important way to restore resources and maintain sustainable development of fisheries. At present, many countries in the world, including China, have carried out diverse enhancement programs on varying temporal and spatial scales, including a large body of juvenile releasing. Meanwhile, studies also have pointed out that many stock enhancements failed to achieve the expected goals while some even led to negative ecological impacts, which sounded a remarkable warning for the future development of enhancement. This study briefly reviewed the progress of fishery stock enhancement in China and abroad, mainly focusing on the scientific problems about the assessment of stock enhancement. We firstly examined the research topics on stocking strategies, including the choice of releasing time and locations, size of juveniles, releasing tactics, juvenile density, genetic effects and their interactions. We then reviewed the methods commonly used in the assessment of stocking effects and the ecological impacts from the ecosystem perspective, and summarized the methods into four categories, that is, assessment models based on mark-recapture, YPR model, population dynamics model and ecosystem model, respectively. Based on the understanding of the complexity of stock enhancement system, we demonstrated the key ecological processes, ecological mechanism and spatial-temporal scales in the processes of enhancement. We further discussed the direction of methodological development for stock enhancement evaluation, and advocated that fundamental principles, ecological effects, and spatial structure should be increasingly incorporated into the development of assessment models. This article indicates that stock enhancement ecosystems have complex structure and dynamics, and stock enhancement should be planned on the basis of a comprehensive ecosystem understanding. Prospective assessment research should be developed to support stock enhancement planning and risk avoidance. This study may provide scientific references for the research and practices of stock enhancement by exploring the shortcomings and development of fisheries enhancement evaluation.

Abstract:Large yellow croaker (Larimichthys crocea) is an important mariculture fish in China. In recent years, the meat quality of cultured L. crocea has gradually declined due to limited culture conditions. Histological characteristics of muscle fibers are commonly used indexes in meat quality evaluation, especially muscle fiber diameter (FD) and density (Fρ). To identify related SNPs and investigate the potential genetic architecture of meat quality, thereby provide basis for meat quality related selection. We conducted a genome-wide association study (GWAS) on muscle fiber related traits of L. crocea, we collected the dorsal muscle of 500 cultured L. crocea and measured the FD and Fρ by using paraffin section and hematoxylin eosin (H.E) stain. The collected samples were genotyped by ddRAD-seq (double-digest restriction-site associated DNA sequencing), and a total of 25 520 and 25 309 high quality SNPs were obtained for FD and Fρ respectively. GWAS analysis identified 6 significantly associated SNPs on 5 chromosomes, and ten candidate genes including lpin2, adcyap1, btg1, lifr, thbs4, gmeb1, slc2a1, myom1, myom2 and tcp11l2 were detected. These genes are involved in biological processes including muscle fiber growth and development, as well as energy metabolism. This is the first study on genomic mapping and analysis of muscle fiber related traits in L. crocea. No gender difference was found in the muscle fiber related traits of two-year-old mature fish. In addition, genes such as lpin2, lifr and btg1 and biological processes including energy metabolism, muscle fiber growth and development may play a role in determining the physical characteristics of meat quality in L. crocea fiber. The results provide theoretical basis and potential molecular tools for subsequent genetic improvement of meat quality traits in cultured L. crocea.

Abstract:In order to study the effect of the diet supplemented with different aquatic weed meals on growth performance, digestive enzyme activity, antioxidant enzyme activity and coloration of Procambarus clarkii, five kinds of aquatic weed meals were added into diet at the level of 15% separately (Diet 2-6), including Elodea nuttallii, Hydrilla verticillata, Vallisneria natans, Ceratophyllum demersum and Alternanthera philoxeroides. The control group (Diet 1) did not contain aquatic weed meals. The six diets were fed to juvenile Procambarus clarkii for 60 days. The results showed that there was no significant difference in survival rate (SR) between Diet 2-6 and Diet 1. The weight gain rate (WGR) and specific growth rate (SGR) in Diet 3-5 were not significantly different from those of Diet 1, and the hepatopancreas index (HSI) of Diet 3 was significantly higher than that of Diet 1. Moreover, in hepatopancreas, the lipase (LPS) activity of Diet 2-6 were significantly higher than Diet 1, LPS and α-amylase (α-AL) activities of Diet 5 were the highest, and the pepsin activity was the highest in Diet 2. The cellulase (CL) activity in Diet 2-3 and 5 were significantly higher than Diet 1. The activities of 4 digestive enzymes in Diet 2-6 were lower than Diet 1 in intestine. The content of total carotenoids in carapace, muscle and ovary, the astaxanthin in carapace and ovary, the lutein and β-carotene in ovary of Diet 3-6 were significantly higher than those of Diet 1. The redness value (a*) and yellowness value (b*) of all treatment groups were significantly higher than Diet 1 in carapace and ovary, while lightness value (L*) was lower. The antioxidant capacity in hepatopancreas, the total superoxide dismutase (T-SOD) activity of Diet 2-6 was significantly higher than Diet 1 and Diet 5 was the highest. The total antioxidant capacity (T-AOC) activity of Diet 4 was the highest while the highest malondialdehyde (MDA) content was found in Diet 2. In serum, Diet 6 had the highest T-AOC activity, and no significant difference was found in T-SOD activity and MDA content between Diet 1-6. In conclusion, diet supplemented with 15% H. verticillata, V. natans, C. demersum meals could meet the growth requirements of P. clarkii, improve the coloration of carapace and ovary, and promote the health status of P. clarkii.

Abstract:Puntius tetrazona is a small tropical ornamental fish with high economic value. Through the method of t-test, the body length (BL), caudal fin length (CL), segment number (SN) and segment length (SL) of caudal fin of P. tetrazona (wild type, WT) and (long fin, LF) were statistically analyzed. The results showed that there was no significant difference in BL between the WT (n=30) and LF (n=30) (P>0.05), but there were significant differences in CL (P<0.000 1), SN (P<0.000 1) and SL (P<0.000 1). At the same time, linear regression analyses were performed on the caudal fin length, segment number and length of caudal fin of WT (n=80) and LF (n=80) P. tetrazona with different body length. The results showed that compared to WT, the caudal fin of LF P. tetrazona grew more rapidly (WT: k=0.28, LF: k=0.62, P<0.000 1), the increasing frequency of the segment number of caudal fin was similar (WT: k=0.79, LF: k=0.82, P=0.006), and the segment length of caudal fin was much greater (WT: k=0.000 4, LF: k=0.006 8, P<0.000 1). Transcriptome analysis of caudal fin of WT and LF adults showed that 56 271 unigenes were obtained from de novo transcriptome assembly. There were 1 304 differentially expressed genes between WT group (n=3) and LF group (n=3), of which 971 genes were up-regulated and 333 genes were down-regulated. The KEGG pathway enrichment analysis showed that the differently expressed genes were significantly enriched into cell cycle and DNA replication signal pathways related to cell proliferation (P<0.05), in which cyclin (cycA, cycB, and cycE) and cyclin-dependent kinase 1 genes were significantly up-regulated. Finally, we determined the expression level of cytoskeleton associated protein 2-like, proliferation marker protein Ki-67, cell division cycle protein 20, protein regulator of cytokinesis 1, up-regulator of cell proliferation and cyclin-dependent kinase 1 by qRT-PCR. The results of qRT-PCR were consistent with those of RNA-seq. The above results showed that a mutated gene in LF P. tetrazona caused the up-regulated expression of cell cycle related genes, which accelerated the cell proliferation rate of caudal fin and resulted in increase of caudal fin segment length, showing the phenotype with a long caudal fin.

Abstract:Fish-light complementation is a clean and efficient production model developed rapidly in recent years, which provides a huge development space for aquaculture. It has the characteristics of clean, low-carbon, and high efficiency. However, there are some problems, such as blank basic research, irregular facility system, insufficient aquaculture technology, and so on. This paper introduces the concept and characteristics of fish-light complementation in detail, analyzes the economic, ecological, and social values of fish-light complementation, and puts forward development suggestions combined with the problems existing in the development process. This study may provide a reference for promoting the healthy and sustainable development of the fish-light complementation industry in China. By fish-light complementation, the solar module has a high power conversion efficiency due to the low surface temperature near the water; the evaporation rate of the water surface is reduced by more than 70% due to solar panels, which saves a lot of water for aquaculture; environmentally friendly aquaculture and power generation models promote the redevelopment of the ecosystem; we can use the smart fishery system to control the aquaculture environment, thereby increasing the growth rate of fish and improving the economic benefits of aquaculture. In addition, from the perspective of energy-saving and emission reduction, if the national average light intensity is combined with the complementary technology of fishing and light, based on the aquaculture area currently in use, it will be able to generate more than 50 megawatt-hours of electricity each year and save about 18 billion tons of coal and reduce 49.85 megatons of carbon dioxide emissions.

Abstract:In order to compare the effects of hydrolysate fish protein of anchovy (HFP), stickwater of anchovy (SW), hydrolysate stickwater of anchovy (HSW), low-temperature fishmeal (L-FM) and high-temperature fishmeal (H-FM) by different production processes in diets, juvenile Pelteobagrus fulvidraco with an initial body weight of (17.69±0.09) g were taken as experimental subjects. 30% super steam fishmeal (FM group) was used as control. HFP, SW, HSW, L-FM and H-FM were added into the test diet respectively, after 8 weeks culture experiment, the effects of 5 different production techniques of anchovy protein on growth performance of yellow catfish were compared. Among them, the addition levels of HFP in the diet were designed to be 25% (HFP25 group), 45% (HFP45 group) and 65% (HFP65 group) of the protein content of fish meal in the FM group. The HFP45 group was used as the reference, and the growth of SW and HSW groups with the same protein content was compared. 8 experimental diets were isonitrogenous and isolipid, with 3 replicates per group and 40 fish per replicate. The results showed that, ① taking the FM group as the control, SGR and FCR in L-FM and H-FM groups were not significantly different; ② the SGR of HFP25 group was decreased by 3.30%, and the FCR was increased by 5.36%, showing no significant difference. SGR of HFP45 and HFP65 groups was decreased by 10.99% and 20.33%, and the FCR was increased by 21.43% and 41.96%, respectively, with significant difference. SGR, protein retention rate (PRR) and fat retention rate (FRR) showed a decreasing trend with the increase of HFP level; ③ among the three protein ingredients of HFP, SW and HSW, HFP group had the highest SGR, and SW group had the lowest SGR, with no significant difference. SGR of HSW group after hydrolysis was 2.25% higher than SW group, with no significant difference. In body composition, there were no significant differences in moisture, crude protein, crude fat and total phosphorus among HFP45, HSW and SW groups, but ash contents were significantly different. The results also showed that there were no significant differences in growth performance and feed utilization of P. fulvidraco between FM, L-FM and H-FM, but the fish health was better than H-FM group. 7.1%HFP could replace 30%fish meal and there was certain equiralence in growth performance, feed utilization and serum biochemical indexes. High dose of HFP added into the diet will have negative effects on the growth and feed utilization. Among the different hydrolysate proteins, HFP had the best growth effect on yellow catfish, and SW had the worst. In addition, HSW after hydrolysis was better than SW. This experiment may provide a basis for improving the utilization efficiency of marine protein resources by studying marine protein materials with different processing technologies.

Abstract:In order to explore the morphological differences of Eleutheronema rhadinum in different geographical groups, this paper was based on 133 E. rhadinum individuals collected from Haimen, Rudong, Zhoushan, Sanmen and Zhuhai from 2018 to 2019, 35 measurable traits and 8 countable traits were measured, and photos of preserved samples were taken for geometric morphological analysis. In the traditional morphological analysis, ANOVA results showed that there were significant differences in other factors except the anal length/body length. Principal component analysis results showed that the variance contribution rates of the first three principal components were 27.724%, 23.959%, 13.535%, and 65.218%. Cluster analysis results showed that there was no significant morphological difference among geographic groups. In the geometric morphology analysis, the results of overprint analysis showed that the marks 5, 4, 7, 7 and 9 had a great influence on the external morphology of E. rhadinum. The results of principal component analysis showed that the first three principal components contributed 21.25%, 18.41%, 12.60% , and the cumulative contribution was 52.25%. The results of principal component cluster analysis showed that there was no morphological difference. In the typical variable analysis results, CV1 contributed 71.059%, CV2 contributed 18.192%, and CV1 and CV2 plotted the two-dimensional scatter diagram of typical variables with staggered distribution of each group sample. The results of Mahalanobis distance and Przewalski distance of different geographical groups showed that there were no significant morphological differences among different geographical groups.The results of both traditional morphology and geometric morphology analysis showed that the morphological characteristics of E. rhadinum among 5 geographical groups were different to a certain extent, and were positively correlated with geographical distance, but had not yet reached the level of population differentiation. This may be due to the geographical isolation between the South China Sea and the East Yellow Sea caused by the fall of sea level during the Pleistocene Glacial Age. However, with the rise of sea level at the end of Pleistocene, because of the strong migration habit of E. rhadinum, some groups could still migrate long distance between the Yellow Sea and the South China Sea, and the presence of fish eggs and larvae that spread with ocean currents, resulted in different levels of gene exchange between populations. As a result, although there are differences in morphological characteristics among different geographical groups, the morphological and genetic differentiation still cannot reach the level of population differentiation.In view of the time difference of E. rhadinum reproductive migration of different geographical groups in the corresponding sea areas, it was suggested that these 5 geographical groups be divided into 1 management unit of Sanmen group, 1 management unit of Zhoushan group, 1 management unit of Rudong group and Haimen group, and another independent management unit of Zhuhai group. In order to protect the sustainable development of fishery resources and guarantee the livelihood of fishermen, targeted management policies should be further formulated and implemented according to four management units for five geographical groups.

Abstract:Nile tilapia (Oreochromis niloticus) is a main aquaculture fish product in China, which is famous for its delicious taste, no intermuscular bone and high nutrition. Currently, it has been observed that the muscle elasticity of O. niloticus can be effectively improved by feeding with Faba bean meal. This kind of O. niloticus was named crisp O. niloticus which has become an economically important freshwater fish species with high economic value. However, little is known about the muscular features between crisp and normal O. niloticus. To investigate the differences of texture properties and nutritional components between crisp and normal O. niloticus, the texture properties, basic chemical composition, free amino acid composition, fatty acids composition and sensory evaluation were measured in this study. Both texture profile analysis and sensory evaluation results indicated that the hardness, springiness and chewiness between crisp and normal O. niloticus muscles were significantly different (P <0.05). For the basic chemical composition, the contents of crude protein and ash content of two kinds of O. niloticus were similar, while the water content of crisp one was lower whereas crude fat was higher than the normal one (P <0.05). Fatty acids composition analysis revealed that the polyunsaturated fatty acids level of crisp O. niloticus was significantly higher than the normal O. niloticus with great nutritional value (P <0.05). Especially, the content of linoleic acids, eicosapentaenoic acids and docosahexaenoic acids of crisp O. niloticus were 2.12, 3.36 and 3.71 times higher than the normal ones, respectively. For free amino acids, the essential amino acids and umami amino acids of crisp O. niloticus were significantly higher than normal one excepting lysine (P <0.05). This study showed that the physical texture, water content, fatty acid content and free amino acid composition of crisp O. niloticus were significantly different when compared with the normal one.

Abstract:Ommastrephes bartramii is one of the important and significant economic species in the Northwest Pacific Ocean, and the variation in biomass is susceptible to the climate change, such as El Ni?o. In this study, we assumed that the oceanic Ni?o index (ONI) affected the parameters, including intrinsic rate of growth (r), carrying capacity (K), respectively and simultaneously, of population dynamics model for O. bartramii. Thus, four surplus production models, Schaefer’s model of surplus production (SP) and three environmentally dependent surplus production (EDSP) models (E_r-EDSP, E_K-EDSP and E_r-E_K-EDSP) were developed to evaluate the trend of the stock dynamics of O. bartramii in the Northwest Pacific. The results showed that the Deviance Information Criterion (DIC) values of three EDSP models were less than the DIC value of SP model. Moreover, the E_r-E_K-EDSP with the smallest DIC value served as the optimal model. The estimated Maximum Sustainable Yield (MSY) value was 39.26×10⁴ tons. From 1994 to 2017, the fishing mortality rate (F_t) of O. bartramii was far lower than the target mortality rate (F_tar) and the fishing mortality rate at the level of MSY (F_MSY). In 2017, the stock resources of O. bartramii in the Northwest Pacific Ocean were less than the corresponding resources at the level of MSY (B_MSY). Currently, the O. bartramii stock in the Northwest Pacific is being overfished or was being overfished. The conclusion could be used for sustainable development and management of O. bartramii in the Northwest Pacific Ocean.

Abstract:In order to understand the differences of nutritional ingredients of muscle in Opsariichthys bidens under wild, pond and factory farming conditions, a comparative study was conducted on morphological indices, nutrient composition, amino acid content, fatty acid content, physicochemical property, heavy metal content of muscle. The results indicated that the muscle phenylalanine, aspartic acid, total essential amino acid, total non-essential amino acid and drip loss of O. bidens in wild were significantly higher than those in pond; the visceral body ratio, muscle crude protein, branched chain amino acid/aromatic amino acids, C16:0 and cooking rate were significantly lower than those in factory, but the moisture, methionine, sulfur-containing amino acids, C18:3n6, saturated fatty acid, lead, cadmium and copper were higher; no significant difference was found in the condition factor, muscle valine, leucine, threonine, lysine, isoleucine, glutamate, tyrosine, arginine, total amino acids, total semi-essential amino acids, flavor amino acid, bitter amino acid, delicious amino acid, C20:0, C20:2, C22:2, C22:1n9 and C20:5n3 of O. bidens between wild and factory. The results showed that compared with the wild and pond, the factory farming can increase the muscle crude protein, total amino acid, C20:5n3, cooking rate, and reduce drip loss, saturated fatty acid, cadmium, lead and copper, which is a better culture mode of O. bidens.

Abstract:As the foundation for ecological engineering of marine ranching, artificial reefs play an important role in the restoration of marine ecological environment and the proliferation of fishery resources. With a large number of artificial reefs, the seabed of marine ranching has gradually transformed into highly heterogeneous benthic habitats, which directly affects the development and reproduction of bottom organisms. How to accurately identify seabed habitats has become an important issue in the benthic ecological research of marine ranching, and remote sensing of the seabed using acoustic technique combined or individually are providing solutions to this problem. Currently, the acoustic seabed classification technique has been applied to ecological research in many sea areas successfully, but it is rarely used in marine ranching. Also, the science of acoustic seabed classification is at its nascence, and there is still no widely accepted agreement about the standardization of instruments and methods. Focusing on the application of acoustic technique in seabed classification of marine ranching, we developed a new method of seabed telemetry and identification based on side scan sonar (SSS) and multi-beam echo sounder (MBES), and applied it in Tianjin Marine Ranching. The SSS and MBES acoustic images objectively reflect the hardness and topography of seabed respectively, which closely relates to seabed type. But most seabed types are not directly measurable using remote survey techniques. It is always necessary to measure the seabed types using in situ ground truthing methods, which can be linked in some way to the characteristics of acoustic images, and then the seabed types can be identified and classified by using acoustic images. In our research, 70 seabed in-situ samples were analyzed and connected with the corresponding acoustic images, and the results show that key image features to identify the seabed type were brightness and texture of SSS image and topography derived from MBES image. Based on the believable relationship between seabed type and acoustic image characteristic, the seabed type of Tianjin Marine Ranching was identified, classified and quantified. The results show that ① six seabed types were found in Tianjin Marine Ranching, including artificial reefs, oysters, mud, clam-mud, oyster-mud and shell-mud, and the accuracy of seabed classification method based on acoustic characteristics is 90%, which can meet the needs of benthic ecological research in marine ranching; ② the mud seabed has subsided to 58.13%, and the shellfish seabed has increased to 7.96%, which demonstrates that the shellfish proliferated in Tianjin Marine Ranching; ③ 0.266 km² of new oyster reef are closely surrounding artificial reefs, and 0.313 km² of oyster-mud seabed will be developed into oyster reef, which verifies the restoration effect of Tianjin Marine Ranching on living oyster reef. Compared with conventional benthic survey methods, our method of acoustic seabed classification based on high-precision acoustic images can avoid sampling errors, reduce human disturbance, discover accurate position of shellfish and improve the accuracy of seabed classification. This study explored the acoustic classification method suitable for the seabed of marine ranching, discussed the complement and perfection of acoustic technique to traditional benthic survey methods, clarified the close relationship between marine ranching seabed types and acoustic image characteristics, and verified the restoration effect marine ranching on oyster reefs. Our research results can be effectively applied to coastal habitat restoration, accurate assessment of shellfish resources, and the evolution mechanism of oyster reefs.

Abstract:Shellfish shell color often exhibits polymorphism, and shell color can be used as a marker color for excellent trait and used in the breeding of improved shellfish species. In order to explore the relationship between shell-color trait of clam Cyclina sinensis and its growth and nutritional components, we measured and analyzed the growth indicators and nutritional components of individuals with different shell colors. The results showed that the wet weight, shell length, wet weight of pipes and gills of the purple-shell individuals were significantly higher than those of the white-shell individuals (P<0.05), and shell width and wet weight of mantle tissue were extremely significantly higher than those of white-shell individuals (P<0.01). The content of crude fat and crude protein of the edible parts from purple-shell individuals were extremely significantly higher than those of the white-shell individuals (P<0.01). The ratios of essential amino acids to total amino acids in purple- and white-shell individuals were 37.46% and 37.02%, respectively, and this ratio of purple-shell individuals was significantly higher than that of white-shell individuals (P<0.05); the ratios of essential amino acids to non-essential amino acids were 67.72% and 66.60%, and this ratio of purple-shell individuals was significantly higher than that of white-shell individuals (P<0.05), indicating that the amino acid balance effect in the purple-shell individuals was better than that of white-shell individuals, and they were all high-quality proteins. The monounsaturated fatty acids of purple- and white-shell individuals are mainly palmitic acid, accounting for 9.97% and 9.85% of the total fatty acids, respectively; Polyunsaturated fatty acids mainly consist of EPA and DHA, of which EPA accounts for 6.64% and 6.54% of the total fatty acids in purple- and white-shell individuals respectively, and DHA accounts for 8.00% and 8.51% of the total fatty acids respectively. Taken together, it suggests that there are certain differences in growth and nutrition between purple- and white-shell individuals and a certain positive relationship between purple shell traits and their growth and nutrition, which provides a theoretical basis for using purple-shell trait as genetic marker in clam breeding.

Abstract:The improved strain (HR-5) of Pyropia haitanensis was characterized by thin blade, good taste, fast growing and high production of conchospores. In order to develop it into a new variety, the contents of crude protein, total amino acid and free amino acid of HR-5 strain and the native cultivated strain (WT-dt) of P. haitanensis cultivated in mariculture farm were determined in this study. The results showed that, ① The contents of crude protein from the first three harvests' blades were 45.2%-38.0% in HR-5 strain, and were 39.5%-33.2% in WT-dt strain, the former was significantly higher than the latter in three harvest periods (P<0.05), and with the increase of harvesting time, the contents of crude protein from both strains decreased gradually. ② The contents of total amino acids were 361.8-287.4 mg/g in HR-5 strain, and were 321.8-264.8 mg/g in WT-dt strain, the former was significantly higher than the latter in three harvest periods (P<0.05), and with the increase of harvesting time, the contents of total amino acids and essential amino acids from both strains decreased gradually. ③ The contents of free amino acids were 3 391.8-1 983.2 mg/100 g in HR-5 strain, and were 2 930.2-2 046.7 mg/100 g in WT-dt strain. The contents of free amino acids of HR-5 strain in the first and second harvest periods were significantly higher than those of WT-dt strain (P<0.05). ④ The contents of mainly flavor amino acids of HR-5 strain were significantly higher than those of WT-dt strain in three harvest periods (P<0.05), and with the increase of harvesting time, the contents of free amino acids and flavor amino acids from both strains decreased gradually. The above results confirmed that the contents of crude protein, total amino acid, free amino acid and mainly flavor amino acid of HR-5 strain were higher than those of WT-dt strain, and that’s the reason why the taste of the former were better than that of the latter. This study also provided basic data for developing HR-5 strain into a new variety of P. haitanensis.

Abstract:With the development of artificial intelligence, big data, machine learning, computer vision and other technologies, convolutional neural network (CNN) is increasingly used in the field of image recognition, which greatly improves the efficiency and accuracy of recognition. Machine learning is data-driven and requires large amounts of data as a basis for experimentation. The richness and diversity of image data sets are crucial to the performance and expressive ability of convolutional neural network models. However, the existing fish image data set resources are relatively scarce, and the training set and test set samples are severely lacking. This makes it difficult to train neural network models, and it is difficult to meet the needs of deep convolutional neural network model optimization and performance improvement. A basic image data set for fish species classification was constructed by using a combination of web crawlers and manual camera collection in the laboratory. Larimichthys crocea, Hypophthalmichthys molitrix, Cyprinus carpio, Cololabis saira and Aristichthys nobilis were used as the test objects in this paper. First, we used web crawlers on the web to obtain pictures of these species of fish, and then, in a laboratory environment, we used cameras to take a large number of photos of these species of fish. In view of the problems of different scales and uncertain formats of images, image batch processing, unified data preprocessing was performed on all the acquired images, and the basic data set was enhanced through content transformation and scale transformation. The dataset was further enriched through this process and the image collection and induction of 7 993 samples were completed. On the basis of parameter sharing and local connectivity, a convolutional neural network model for fish recognition is constructed; the ReLU function was used as the activation function to improve the performance of the algorithm; the dropout and regularization were used to avoid overfitting. The test results showed that: the convolutional neural network fish species recognition model constructed in this study have good recognition accuracy and generalization ability. As the number of iterations increased, the performance of the convolutional neural network model gradually improved. It reached the best when the number of iterations came to 1 000. The accuracy of the model was 96.56%. The model adopted the machine learning method of supervised learning. Based on the CNN model, it realized the classification of five common fish species, with high recognition accuracy and good stability. The model has provided a new theoretical calculation model for the species identification of farmed fish.

Abstract:Excessive deposition of fish fat is a very common phenomenon in artificially farmed fish. The widespread use of high-fat diets is an important cause for this consequence. Long-term and excessive use of high-fat diets can cause fat deposition in fish organs or tissues. Liver cells are the main place for fat synthesis in fish, and 90% of the fat is synthesized in liver cells. Excessive fat deposits in the liver can have a negative impact on the health of the fish. Chinese herbal medicine is the current research focus of anti-immune stress agents. Berberine is an alkaloid isolated from the traditional Chinese medicine Rhizoma Coptidis. It has the effects of protecting the liver, antioxidant, anti-inflammatory, hypoglycemia and lipid-lowering. Preliminary research in our laboratory found that berberine as a functional feed additive can significantly inhibit the process of oxidative stress, reduce cell apoptosis and enhance the immunity of fish fed with high-fat diets. In order to explore the effect of berberine on the lipid metabonomics of Danio rerio liver cells induced by high fat, D. rerio cells were used as experimental materials, and sodium palmitate (0.25 mmol/L, 24 h) was used to induce liver cell lipid deposition models. After treatment with berberine (25 μmol/L, 6 h), the cells were collected. Using high performance liquid chromatography-mass spectrometry technology for lipid metabolomics analysis, the lipid metabolites of different treatments of D. rerio liver cells were screened and identified, and the gene expression of lipid metabolism-related factors was detected. The results showed that compared with the control group, a total of 1 761 differential ions were screened in the high-fat group, among which 147 differential metabolites were identified, and 123 were increased and 24 were decreased; the high-fat + berberine group screened a total of 2 728 differential ions, among which 346 different metabolites were identified, 139 increased and 207 decreased. Compared with the high-fat group, the high-fat + berberine group screened a total of 1 605 differential ions, of which 259 differential metabolites were identified, and 45 increased and 204 decreased. Further studies on the metabolic pathways of unsaturated fatty acids found that the content of differential metabolites dihomo-γ-linolenic acid (DGLA) and dihomo-α-linolenic acid (ETA) increased significantly in the high-fat group, and the addition of berberine would make their content decrease significantly; compared with the control group, there was no significant difference in the content of DGLA and ETA in the high-fat + berberine group. By detecting the expression of DGLA and ETA decomposition-related enzyme genes (atgl, hsl), it was found that compared with the control group, both of the high-fat group were significantly reduced, and both were significantly increased after the addition of berberinei; detection of the expression levels of synthesis-related enzyme genes (acc, elovl6, elovl7a, scdb, fas and fads2), showed that compared with the control group, the high-fat group intracellular acc, elovl6 and scdb expression were significantly increased, fads2 expression decreased significantly, and fads2 expression in cells increased significantly after berberine was added, and fas, elovl6 and scdb expressions were significantly decreased. To sum up, the induction of high fat inhibits the expression of lipid-related genes, promotes the expression of lipid-synthesis-related genes, and causes excessive deposition of fat in cells. Adding a proper amount of berberine can promote the expression of lipid-related genes and inhibit the expression of lipid synthesis-related genes, thereby down-regulating the content of DGLA and ETA, effectively alleviated the damage induced by sodium palmitate to liver cells.

Abstract:The Sutong section in the lower reaches of the Yangtze River is located in the estuary section and close to the estuary of the Yangtze River, which is the migration channel for Coilia nasus. Recent studies have shown that C. nasus adult fish resources still indicate a trend downwards. It’s of great significance to conduct research on C. nasus early resources, which is a supplementary group of adult fish resources. In this study, early resource surveys were conducted in Sutong section for a total of 84 days from May to August each year in 2018-2020 to reveal the spatial and temporal distribution characteristics of C. nasus early resources. A total of 646 fertilized eggs of C. nasus were collected during the survey period, including 328 eggs collected in 2019 accounting for 50.77% of all. The mean abundance of eggs collected in May and June was significantly higher than that in the other months of collection (P<0.05), where as no fertilized eggs were collected in April. The peak of fertilized eggs collected in each year was on 15 May (4.96 ind./100 m³), 16 June (26.48 ind./100 m³) and 24 May (26.11 ind./100 m³), respectively. Pearson correlation analysis showed significant differences in the spatial distribution of the sampled sections (P<0.05), with mean abundance distribution on the left bank (1.42 ind./100 m³) > right bank (0.87 ind./100 m³) > centre of the river (0.69 ind./100 m³). The mean abundance and frequency of fertilized eggs of C. nasus collected in the downstream S1 (waters of Lvhua Town in Chongming Island) and S2 (waters of Xintonghaisha, Haimen City), midstream S5 (waters of Gangzha District in Nantong) and upstream S8 (waters of Changqing Sha Dian Yuan in Rugao) of the Sutong section were significantly higher than those of other collection sections (P<0.05). The analysis of environmental factors showed that the abundance of fertilized eggs of C. nasus was negatively correlated with temperature (P<0.01), and the abundance of fertilized eggs of C. nasus was higher in the range of 21.1-25.3 °C and 6.80-7.41 mg/L of dissolved oxygen. The results showed that May and June were the peak spawning months for C. nasus in Sutong section, and the temperature range of 21.1-25.3 °C and dissolved oxygen range of 6.80-7.41 mg/L were suitable for C. nasus spawning. It is speculated that the waters in Lvhua Town of Chongming Island, Xin Tonghaisha of Haimen, Nantong Gangzha District and Changqing Sha Diangyuan of Rugao are potential spawning grounds for C. nasus.

Abstract:Type Ⅱ interferon, also termed IFN-γ (IFN-γ), is one of the key cytokines involved in the immune response of T helper 1 (Th1) lymphocytes. Fish and mammalian type Ⅱ IFN-γs are homologs, but unlike mammals which contain a single copy of IFN-γ gene, teleost fish have two duplicated copies, namely IFN-γ and IFN-γ related (IFN-γrel) factor. To date, the expression and functions of fish IFN-γs have been well documented, however fish IFN-γrels have not been extensively investigated. For example, the cells producing IFN-γ and IFN-γrel are unclear, whether they have differences in functions has also been debated. In this study, the IFN-γ and IFN-γrel recombinant proteins of Ctenopharyngodon idella (Ci) were expressed in E. coli DE3 cells. The results showed that the CiIFN-γ protein was soluble, while the CiIFN-γrel protein was insoluble. The recombinant IFN-γ and IFN-γrel proteins were purified using affinity chromatography and size exclusion chromatography and used for preparation of monoclonal antibodies in mice. Four antibodies with high specificity and affinity were obtained after screening by Western blotting. It was revealed that the monoclonal CiIFN-γ antibodies did not cross-react with the CiIFN-γrel protein and vice versa. Two of the antibodies were labeled with FITC fluorescein and could be used for immunofluorescent analysis and flow cytometry. Further, C. idella IFN-γ and IFN-γrel monoclonal antibodies could not recognize their respective homologs from Danio rerio. To our knowledge, this is the first study reporting the preparation of IFN-γrel monoclonal antibody in fish. The availability of CiIFN-γ and CiIFN-γrel monoclonal antibodies will provide valuable information to investigate the cellular sources and biological functions of type Ⅱ IFNs in C. idella.

Abstract:Sinibrama taeniatus is a rare and small economic fish which is distributed in the upper reaches of the Yangtze River. S. taeniatus can reproduce twice a year in the wild, while the reproductive cycle of S. taeniatus reared at the temperature of 26 °C is only 14 days. Low temperature is a major factor limiting the reproduction of the fish in the wild, especially in winter. We found that the low temperature of 11 °C significantly inhibited the ovarian development of S. taeniatus. To explore the effects of low temperature on ovarian development, the female S. taeniatus after spawning were reared at a low temperature of 11 °C (LT groups) for two weeks, and the fish reared at the temperature of 26 °C (OT groups) as control group. We compared the ovarian development of the LT groups and OT groups. The morphological and histological results showed that the ovarian development was inhibited in the LT groups and that the oocytes were underdeveloped and degenerated. Besides, the atretic follicles were observed in the ovaries of the LT groups. The results of enzyme-linked immunosorbent assay and qPCR showed that the secretion of FSH and DHP, and the gene expression of fshr, lhcgr, pgr, esr1, and ar were significantly inhibited by the low temperature. Transcriptome sequencing results showed that the differentially expressed genes were significantly enriched in steroid hormone synthesis, cell growth and proliferation, apoptosis, and autophagy pathways, indicating these pathways were affected by the low temperature significantly. The expression of genes involved in pro-apoptosis (i.e. bax, tnf, and tp53) was up-regulated in the LT groups. However, the expressions of genes involved in steroid hormone synthesis, oocyte development, cell growth and proliferation, and anti-apoptosis, viz., StAR, cyp17a1, hsd3b, cyp19a2, hsd17b1, vtg1, zp4, mmp9, mmp15, ccni, cdk16, igf1r, egfr, nobox, and bcl2 were significantly down-regulated in the LT groups. It suggests that the low temperature may inhibit the synthesis and action of reproductive hormones, limit oocyte growth and proliferation, and promote autophagy and apoptosis of follicles which results in follicular atresia. It provides a theoretical basis for conservation biology and artificial reproduction of S. taeniatus.

Abstract:Tachypleus tridentatus belongs to the arthropod phylum, and its blood contains a lot of hemocyanin. Hemocyanin plays an important role in the organism, such as transporting oxygen, immune defense, and energy storage. Hemocyanin also has many applications in vitro, such as being made into biosensors and immune products. This study aims to obtain high-purity hemocyanin of T. tridentatus and explore its potential application value. In this study, hemocyanin was extracted from hemolymph of T. tridentatus and purified with AKTA protein purification system. The purified hemocyanin was qualitatively analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS) technology. Finally, 22 amino acid sequences of hemocyanin from 5 species were downloaded from the uniprot protein database, then the N-J phylogenetic tree was constructed. The results showed that the purity of the purified hemocyanin was high. Twelve types of hemocyanin subunits were identified from hemocyanin of T. tridentatus, including Hemocyanin subunit Ⅰ, Hemocyanin subunit Ⅱ, Hemocyanin subunit Ⅲa, Hemocyanin subunit Ⅲb, Hemocyanin subunit Ⅳ, Hemocyanin subunit Ⅴ, Hemocyanin subunit Ⅵ, etc. According to the uniprot database, these subunits were first found in Carcinoscorpius rotundicauda and Limulus polyphemus. The N-J phylogenetic tree shows that hemocyanin of Tachypleus tridentatus has a high degree of homology with C. rotundicauda and L. polyphemus. It was also found that there was a close evolutionary relationship of hemocyanin between hemocyanin of Limulidae and Litopenaeus vannamei and Scylla serrata, which suggests that the function of hemocyanin in T. tridentatus can be inferred from the function of hemocyanin in other species. This study obtained high-purity hemocyanin from hemolymph of T. tridentatus, and the results of this study are helpful to the function prediction and application research of Chinese horseshoe crab hemocyanin.